93-98 Supra Twin Turbo Supra FAQ’s

frequently asked questions
Following are a list of frequently asked questions and answers relating to maintenance and upgrading of the toyota supra mkiv twin turbo . Question section headers are in blue, answer headers are in red.
additional info:
repair manuals | mkiv specifications
credits: david e., steve v., john c., sean m.
questions
the questions will be indexed here at the top. click on a question to go directly to the answer. all the answers to the questions are at the end of this section.
basic performance upgrades (bpu)
  1. my tt is currently stock, but i want to improve its performance. what should i do?
  2. how much will bpu cost me?
  3. i have a ’96-’98 mkiv with the obdii computer. can I still do bpu’s?
  4. what is the free fuel cut defenser (ffcd)?
  5. i didn’t do the ffcd, and now my check engine light has come on. what can i do?
  6. since i’m upgrading, should i replace the air intake as well?
advanced performance upgrades (apu)
  1. what about the stock fuel system in the tt? does it need to be upgraded as well?
  2. i need some instructions for installing the hks vpc
  3. i need some instructions for installing an upgraded fuel system
  4. which single/twin turbo kits fits my supra best? their potential?
  5. what exactly is a/r on a turbo?
engine
general description

  1. what is the difference between an i-6 engine and a v-6?
  2. what is meant by “…designed as a non-interference engine”?
  3. i sometimes hear slight detonation when boosting.
  4. what causes knocking, pinging, detonation, and pre-ignition?

specifications

  1. i want to have the motor bored & stroked like my chevy. what’s available?

features

  1. what spark plugs should i use?
  2. i’m using stock plugs, and my car isn’t running quite right.
  3. i want to replace the spark plugs on my supra tt. what are the steps?
  4. how can i read my sparkplugs?
  5. the engine misses at high boost.
  6. how do i check the engine trouble codes?

cylinder head & valvetrain

  1. what does dis mean? is it an abbreviation for distributor?
  2. how about sfi?
  3. how can i do a cylinder leak-down (clt) test?

block

  1. i thought the supra was a high performance engine. why doesn’t it have four bolt mains like a camaro?

pistons & rods

  1. are aftermarket forged pistons and rods a good idea?

crankshaft & torsional damper

  1. can I pull the harmonic balancer off, replace it with an underdrive pulley and pick up 10-15 horsepower?

lubrication system

  1. which type/brand of oil and filter should i use for the mkiv tt engine?
  2. how often should i change my oil?
  3. is it difficult to change the oil? how long should it take?
  4. what specification and oil weight should i use?
  5. aren’t all engine oils basically the same?
  6. how can i know if my oil is not performing?
  7. how important is it for my turbos/engine to use the right oil?
  8. when to switch to synthetic? what kind?
  9. what is the best way to change the oil on my mkiv?
  10. a “quickie lube” place changed my oil and wanted to put in an additive. they said my engine would get 30% better gas mileage and make at least 20% more power.
  11. where can i learn more about oil?
  12. why does my oil look dirty when i check my oil level?

cooling system

  1. how do i know if my coolant needs changing?
  2. which coolant should i use?
  3. what’s the proper mix of coolant and water?
  4. why distilled water?
  5. why is such a low concentration of coolant recommended? i always thought that a 50/50 mix of coolant and water was the best protection for my cooling system.
  6. doh, i didn’t sign up for a course in heat transfer. just tell me the right proportion of coolant and water to put in my system.
  7. what’s the best way to flush & clean the cooling system?
  8. my car seems to run very hot in the TX or AZ summer and gets terrible gas mileage. should i try a lower temperature thermostat?
  9. i think i’ll take the thermostat out altogether. won’t this help cool the engine even more?
  10. what about electric fans, do they help?
  11. how ’bout that cool looking trd radiator cap. will that make it cool better, and the car go faster?
  12. i live in denver, and in the summertime when i park my car and turn off the engine, i hear gurgling noises. once i even saw steaming coolant coming out of the radiator into the overflow tank. what’s wrong?
  13. my car overheats since i installed (pick one or more):
    1) a fmic
    2) oil cooler
    3) electric fans
    4) started road racing
    5) went bpu+++
    what’s wrong?

intake system

  1. what can I do to improve the performance of the intake air system?

exhaust system

  1. i “accidentally” ran some (pick one):
    1. leaded gasoline
    2. octane booster
    3. mysterious fuel additive from a “quickie lube” place through my car thinking it would make it go faster. now it runs terrible and my gas mileage is terrible.
  2. my supra emits smoke when i start up. what does the smoke indicate?
  3. 3. my car is (insert modification level here), do i need an egr blockoff plate?
turbo system
  1. how does the stts (sequential twin-turbo setup) work?
  2. what does a vsv do?
  3. will a front mount intercooler (fmic) help my bpu car?
  4. i don’t want to put a big fmic in front of my radiator, can i get an upgraded sidemount?
  5. how about upgraded ic piping?
  6. my ic hoses pop off under high boost. what should i do?
  7. my car won’t boost very high. it stumbles and lets out black smoke while accelerating. what is wrong? i have the stock mass air sensor (maf).
  8. my second turbo doesn’t kick in immediately after i downshift. what is wrong?
  9. my boost is acting strangely, and i do not have a boost leak. what could be wrong?
  10. how do i to troubleshoot the sequential system?
transmission and differential
  1. which transmission is better, the 6-speed or the auto? can either of them handle the additional horsepower?
  2. what fluid should I use in my tt 6-speed? how about in the differential?
  3. my 6-speed transmission makes a rattling sound at low speeds. should i worry?
  4. how do i check the torsen differential oil?
  5. should i get a lightweight flywheel?
brakes
  1. what minimal brake upgrades will i need for road race tracks?
  2. i want to remove my rear brake disc but it will not come off. what should i do?
suspension
  1. what is a good street alignment?
  2. what is the stock alignment?
wheels and tires
  1. what kind of tires are the best for sport driving? how about for drag racing?
  2. i’m thinking about getting aftermarket wheels. how much do the stock wheels weigh?
  3. what are the names of the wheel parts?
  4. what is offset?
  5. what is the size and offset of the stock wheels?
n2o – nitrous oxide
  1. i run nitrous. which spark plug should i run?
electrical
  1. my airbag light has come on after i opened the dashboard. how do i turn it off?
  2. i have the 7-speaker system in my mkiv, and i want to upgrade the speakers. what fits?
  3. i want to improve the stock stereo. what’s good?
  4. how do i clear the “check engine” light?
  5. how do i reset my ecu?
  6. is it possible to swap out 93-96 headlights with the new 97-98 headlights?
  7. i want to use a turbo timer, but it seems to interfere with the factory alarm.
  8. i want to install an aftermarket alarm/keyless entry system and i can’t find the wiring color code for a 93-94′ tt?
body
  1. i want to keep my Supra looking its best. what wax / polish should i use?
  2. at freeway speeds, my hood vibrates up and down. is there a problem with it opening at higher speeds?
  3. i get a chirping sound from my door. what can i do?
  4. does anyone sell a car cover specifically for the mkiv supra that would fit over the wing?
  5. my headlights are fogged up inside. what can i do?
  6. there is a rattle coming from the hatch area. what is it?
  7. can i get an advice on the care and up keeping of my supra?
drag racing
  1. what are the basics of drag racing?
  2. what is the best way to launch my tt for a drag race?
  3. what is a good autocross alignment?
general faq
  1. i can’t understand many of the posts – they all contain acronyms i’ve never seen before.
  2. what’s the equation which relates crank horsepower to speed at the end of the 1/4 mile?
  3. i’m going to store my supra for some time. how should i prepare it?
  4. there’s no cup holder. where do i put my drink?
  5. what is the difference between the export mkiv supras and japanese mkiv supras?
  6. what is horsepower?
  7. where can i get the repair manuals for my mkiv supra?
  8. where can i get discounts on stock supra parts?
  9. i see some list members have white gauges. where can i get those?
  10. what is the right way to dyno the supra tt?
  11. what are the production numbers for the mkiv supra?
  12. i need help with my toyota warranty. what should i do to make the process go by easy?
  13. how much does the supra weigh and what is the weight distribution?
  14. i understand some years only came with automatics. which ones?
  15. is any year supra more desirable than others?
  16. how hard is it to convert an auto supra to a 6 speed?
  17. are there any common problems to look out for when shopping for a supra?
answers
following are the list of answers to the above questions. the questions are included with this section to improve referencing.
bpu – basic performance upgrade
1. my tt is currently stock, but i want to improve its performance. what should i do?
glad to hear you’re ready to “really” join the tt club! we have found that the tt responds very well to the following list of basic performance upgrade s (bpus). these upgrades are proven (by us naturally!!) to have a high degree of reproducibility from car to car if you install all of the following:

  1. exhaust system (most of the major brand name exhausts are fine)
  2. downpipe with or without high flow catalytic converter (rod millan, speedtek, random technology, stillen, uprd, powerhouse & spp)
  3. ebc or mbc (electronic/manual boost controller), not boost controllers w/ fuzzy logic (e.g.. profec a and hks evc)
  4. fuel cut defenser (greddy bcc – highly recommended by the mkiv.com members. read why hks fcd is the same as the ffcd (using the hks fcd or the ffcd is only recommended if you have the ttc mod and 12v mod)

with the bpu installed, you can expect to obtain approximately 370-410 rear wheel horsepower (rwhp). damn, you gotta love the supra tt!!

you will also want to install a boost gauge to monitor how much boost you are running. obviously running more boost is going to decrease the life of your turbos (by how much is not really known) so you will want to watch this. a few turbos don’t last long at all at higher than stock boost levels, but most seem to take the increased boost just fine. most people think the best trade off is no more than 18 psi although some have had success and longevity with higher boost. a conservative number would be to run 15 psi low boost with occasional runs to 17 psi if you get an ebc that is easily adjustable on the fly. even with a supra, you gotta be willing to pay to play…
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2. how much will bpu cost me?
around ~$2k if you go for the electronic boost controller instead of using a manual boost controller or a bleeder valve. not bad, huh? try to get that kind of serious hp for the money in any other performance ride!!
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3. i have a ’96-’98 mkiv with the obdii computer. can i still do bpu?
yes, they work just fine with the obdii computer. however, when you install the dp you will get the ‘check engine’ light continuously because you are disconnecting the second oxygen sensor from the catalytic converter. however, that second sensor has no effect on performance. click here for how to clear the ‘check engine’ light. a dp with high flow cat will accommodate the obdii o2 sensors and will not alert the mil. alternatively, you can purchase an o2 simulator that will trick the computer into thinking the catalytic converter is still there.
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4. what is the free fuel cut defenser (ffcd)? *read why the greddy bcc is better then the ffcd mod here & here.
The free fcd is basically a low-buck way to bypass the computer’s fuel cut control. this is critical to maximizing your hp output when your boost levels go over say, 14-15 lbs of boost. here’s how you do it within 5 minutes and for less than a dollar!! this modification requires no soldering or tapping into the harness and is reversible within minutes. please be aware though that with this mod, you have no fuel cut. you need to ensure you don’t boost too high! to install the “free” fcd, completely remove the 4-inch vacuum line that connects the pressure sensor switch to the “y” connector. (you’ll find the pressure sensor switch on the passenger side of the intake air manifold on the throttle body towards the top. the correct sensor is marked “sensor turbo pressure” in green.) notice that the vacuum line is attached to the bottom of the sensor switch. leave the wire connector attached. cap the bottom of the switch with a 1/8-inch cap. cap off where the 4-inch hose connected at the “y” with another 1/8-inch cap. (note: when you slip the cap onto the sensor turbo pressure, you must make sure not to trap too much air in the cap. one tt owner had some difficulties because the sensor thought it “saw” high boost all the time. just a warning.)
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5. i didn’t do the bcc, and now my check engine light has come on. what can i do?
you need to reset your ecu. see the faq entry on that topic for details
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6. since i’m upgrading, should i replace the air intake as well?
dyno results show that mkiv supras with the bpu and no intake system dyno about the same as those with either a k&n or a hks super mega flow (the gain is minimal). higher horsepower cars will benefit more from the installation of an air intake system. if you must upgrade, the max air airbox with intake has been given high praise by several list members. one upside for some if you get a cone filter upgrade is you will hear a lot of new noises from your engine if you like that sort of thing.
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apu – advanced performance upgrade
1. what about the stock fuel system in the tt? does it need to be upgraded as well?
the stock 2jzgte twin turbo fuel system is a remarkably good system straight from the factory. the in-tank pump, fuel filter, fuel pulsation damper, injectors, and boost dependent fuel pressure regulator are all capable of high fuel flow. toyota did its homework here, as the tt’s fuel pump and injectors both max-out at about the same fuel flow.
fuel pump: the stock pump is a denso unit, capable of supporting up to 450 rear-wheel horsepower (rwhp) reliably. push it up to 500 rwhp, and you start gambling. go past 500 rwhp, and you are flirting with disaster! the pump is controlled by the fuel pump electronic control unit (ecu) located under the plastic panel just behind the rear driver-side shock tower. the ecu controls the pump at two different speeds based on engine load. at low engine loads, the pump is operating at reduced capacity due to reduced voltage from the ecu. once you floor it, however, the fuel pump operates at full capacity. also, the fuel pump ecu is equipped with a fuel pump system diagnostic function.
fuel filter, lines and the “mysterious” fuel pressure pulsation damper: the stock fuel lines are a decent size compared to other cars. there is no need to go to larger lines unless you plan on making over 500 rwhp, at which time you will need to rework the whole system anyway. the stock fuel filter is as good as any after-market unit. the fuel pressure pulsation damper is really no mystery. it is simply designed to minimize the “water hammer” effect in the fuel caused by the fuel pump’s mechanical action and the opening and closing of the injectors. the damper acts to absorb these pressure waves in an attempt to extend fuel pump and injector life. the necessity of this device, however, is questionable. people have reliably run up to 500 rwhp on the stock fuel system after removing this restriction and making sure the rest of the system is in top shape.
fuel rail and injectors: the stock fuel rail and injectors are quality units, capable of supporting the same HP as the stock fuel pump. the injectors are rated at 540 cc/min at 41.2 psi of fuel pressure (~550 cc/min at 43.5 psi), and are a two-hole, side-feed, low resistance design. these injectors enable the hot injector to be cooled by its fuel supply, increasing both hot starting and drivability. push your power past 475 rwhp, however, and your exhaust gas temperatures (egts) may climb due to a leaning-out condition. those pushing the limits of the stock system will need to keep a close eye on this. it would be a good idea to have your injector cleaned and balanced if you plan on pushing 500 rwhp on the stock system.
fuel pressure regulator and fuel tank: the fuel pressure regulator is a boost-dependent style. the regulator controls fuel pressure at around 36 PSI above manifold pressure. so as boost pressure rises, so does fuel pressure. this ensures a nice consistent differential pressure across the injector tip which optimizes spray pattern. the fuel pressure regulator directs all of the excess fuel through the return lines on back to the fuel tank. the fuel tank contains both a main fuel tank and a subtank. this subtank (along with an internal baffle-type design feature called the “jet pump system”) prevents fuel sloshing, and assists the fuel return flow in providing an uninterrupted supply of fuel during high-speed turns and low fuel level conditions, as fuel shifts from one side of the fuel tank to the other.
fuel system options: most people who upgrade their fuel systems are using either the paxton “signature” series, paxton “kamikaze”, or walbro high pressure fuel pump, depending on hp goals. couple one of these pumps with a paxton or earl’s fuel filter,-8 or -10 (an size) stainless braided lines and fittings (earl’s, aeroquip), 720-cc injectors (hks, greddy, rc engineering), and adjustable fuel pressure regulator (aeroquip, paxton, sx), and you end up with a monster fuel system capable of supporting up to 700 rwhp!
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4.which single/twin turbo kits fits my supra best? their potential?take a look at steve v’s turbopage for great information on a lot (if not all) of the different turbos out there that can be used on the 2jz.RPS Kits:
TS04: Most common housings for this turbo are 0.58 and 0.70, it makes about 450 rwhp in the former and 500 rwhp in the latter, spools slightly slower than stock, and can commonly be used on the stock fuel system. This is a good turbo if you have an automatic, and can be daily driven.
T61: Somewhat bigger than the TS04, this turbo can make 550-600 rwhp. It requires an upgraded fuel system. This doesn’t lag too much, a T61 car lags a bit more than stock, but is streetable, if not particularly responsive, could be used for road racing, not sure if I would recommend this turbo for a daily driver.
T66: Capable of making 600-675 rwhp, the T66 is a bigger turbo yet, this is probably as big a turbo as I would recommend for the street, it makes full boost right around 4250 rpm on most cars, a significant amount of lag, but not horrendous… (full boost being 1.5-1.6 bar) This is a very common turbo, and a nice setup for drag racing with some street driving.
T70: Slightly bigger than the T66, the T70 is probably not a streetable turbo. Lag is a couple hundred rpm more than the T66, power output ranges from 650-750 rwhp… perhaps a bit more with headwork… This is a nice turbo for drag racing.
T72+: These turbos are only good for drag cars for the most part, lag is far more than smaller turbos, power outputs are from 750-1000 rwhp.
Twin turbo kit:Using T25/28 ball bearing turbos, this kit will make slightly more than 500 rwhp, while spooling faster than the TS04 0.70… very good choice for a street car that needs more power than BPU.HKS:
GT2540: These twin turbos are used on the UPRD supra, and used in single form on quite a few different cars. Nice turbos, not enormous lag, maybe slightly more lag than their brethren the 2835s, but they spool a little faster too…I’m told that car makes power in the 900 rwhp range on turbo alone, but this could be just a rumor.
GT2835: Probably the most common twin turbos used on supras, this kit is large, and the turbos have a fair amount of lag, they make full boost in the 5000 rpm range, perhaps a bit higher. Very nice top end on this system, and I’ve seen power output in the 700-800 rwhp range fairly consistently with the right fuel support.
T04R: A fairly large single turbo, this comes with a pretty big exhaust A/R stock, 0.96… I would have thought it would be laggy, but my experience with it shows otherwise… it spools a touch faster than a T66, but has a bit more power output capability… it has made power in the 675-750 rwhp range, and is becoming fairly popular because of this.
T51R: This is HKS’s biggest single turbo that is commonly sold, although it isn’t THAT much bigger than the T04R. Probably in between the T66 and T70 in size, the T04R makes full boost in the 5k range, and none has really been able to realize its full power potential… I wouldn’t be surprised at seeing 800+ rwhp from a T51R under the right circumstances… very strong turbo but I wouldn’t use it on a street car personally.Greddy:
T67: The T67 isn’t used on supras very often, its a TD07-25g turbo, more commonly used on MR2s… its capable of right around 600 rwhp, and spools similarly to a T66, so most people choose to go with either the T66 or T61. Again, on the upper limit of streetability.
T78: This is one of the more common turbos used on supras… it makes full boost somewhat past 5000 rpm, but has the potential to make 750+ rwhp… nice turbo, very good top end once it gets spooled… lots of drag cars use it, and its fairly inexpensive now.
T88: Somewhat bigger than the T78, the T88 has close to 1000 rwhp capability, although I would imagine it makes full boost close to 6000 rpm, so a built motor is almost a certainty with this turbo… not too expensive but its not too usable on most supras so…Blitz:
Single: The blitz single turbo uses a K27 turbo and is capable of right around 600-650 rwhp… spools somewhat faster than a T66, and the kit is well made, but you need to modify it to work on the US spec supra, pain in the ass to do.
Twins: Supposedly capable of right around 700 rwhp with about as much lag as the single, haven’t really heard too much about it to corroborate this, but I wouldn’t doubt it… kind of expensive, and this needs heavy modification to work on a US spec supra.Others:
TPC: This turbo supposedly has 625-750 rwhp capability with faster spool up than a T66… don’t know enough about it to really say, but the dyno charts seem to show full boost at right around 4500-5000 rpm, which isn’t TOO bad for a turbo with its power capabilities… not enough people use it to really say.
Fastrax: Fastrax makes all sorts of custom turbos… my experience with them is that they make somewhat more power and spool somewhat faster than the turbos they were built off of… Fastrax has allot of experience in the drag racing scene, and they make high quality products. My Fastrax turbo supposedly has 750-800 rwhp capability while spooling slightly faster than a T66… it certainly spools faster than a T66 in my experience, we’ll have to see how much it puts down on the dyno.
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5. what exactly is a/r of a turbo?
a/r stands for area / radius on the turbine side of a turbo. area being the area of the turbine inlet and radius being the distance from the center of the turbine shaft to the center of the turbine inlet. this picture explains it perfectly. changing this property affects the spool-up and overall flow of a turbo. lower a/r generally reduces spool-up and maximum flow of a turbo.
engine
general descriptionthe 2jz-Gte is a high performance 3.0 liter, inline 6 cylinder engine. it features dual overhead camshafts (dohc), 4 valves per cylinder, twin sequential water-jacketed turbochargers with a common charge air cooler (air to air intercooler). it is a “square” configuration with equal bore and stroke dimensions. it is also designed as a non-interference type engine and both camshafts are driven from a common toothed drive belt.its mate, the 2jz-ge, or naturally aspirated (na) version of the engine, shares the same block casting, but is fitted with higher compression pistons. the two head castings are similar as they both must fit on a common block, but are cast and machined differently to suit the design requirements of the two models. the real differences between the two engines are found in the ancillary systems such as fuel, ignition, intake/exhaust, cooling, and of course the turbochargers and their control system.where similarities or commonality exists between the gte and the ge engine, they will be mentioned, otherwise the descriptions below are for the gte engine.
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1. what is the difference between an i-6 engine and a v-6?
the i-6 Supra engine has all six cylinders “inline”. the camry’s and other models in the toyota lineup use a six-cylinder engine with its cylinders arranged in a “v” like an american v-8. the supra engine is a superior design for smoothness, high performance potential, and ease of modification. sadly, toyota has decided to phase out their i-6 engines in favor of the v-6, for economic and space reasons.
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2. what is meant by “…designed as a non-interference engine”?
by definition, if the design of the paths of the valves and piston causes them to intersect at any point, regardless of the timing, the engine is an interference engine. in practical terms this means that if the camshaft drive system (timing belt) breaks in an interference engine, and several valves are left open or partially open, chances are there will be damaged valves, pistons, and perhaps other components. in a non-interference engine, if the timing belt breaks, the engine will simply stop running, but there will be no damage to it. some honda and dsm engine designs are the interference type.
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3. i sometimes hear slight detonation when boosting.
if this is consistent with any type of readily available fuel, you are probably running too much boost.
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4. what causes knocking, pinging, detonation, and pre-ignition?
detonation and pre-ignition are about the same thing, they just happen at different times in the compression cycle. pre-ignition is either caused by hot spots that pre-ignite the fuel before the spark plug goes off or the actual compression of the air/fuel igniting the mix. remember, when you compress a gas, you heat it up. that’s why too much boost can cause extra high cylinder temperatures and subsequent pre-ignition. a lot of people call this detonation, but it isn’t. you can feel pre-ignition, it will feel like rough power. detonation occurs after the spark. if the air/fuel ratio is too lean, you don’t get a nice progression of the flame front from the spark plug towards the bottom of the cylinder. the burn will be uneven, and you will develop many different flame fronts going in many different directions. as these flame fronts collide, they make noise and you hear the knocking and pinging. more importantly, the oxygen is going to react with something. better it react with gas than metal. both of these will lead to high EGTs. now hesitation can be caused by both lean and rich conditions. usually by too rich conditions. you basically flood out the spark and it doesn’t light off the air/fuel mixture. this will lead to black smoke out the tail pipe and low EGTs. if you run too lean to get a hesitation, you will be way past the point that your EGTs should be sky high. another thing to check is make sure all injectors are firing. you should be able to do this at idle by putting a screwdriver on the injector and the other end butted up against your ear. or, you can sometimes feel them by putting the tip of your finger nail on the injector and pushing a little hard. the vibration is carried through the bone and you feel it.
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specificationsbore & stroke of the engine are both 86mm (3.39″) giving a true displacement of 2997cm3 (183in3). The turbocharged (gte) engine has a compression ratio of 8.5:1, while the na (ge) engine is raised to 10.0:1 using different pistons and head configuration. the engine is internally balanced, has a firing order of 1-5-3-6-2-4, and produces a maximum horsepower of 320 (sae net) @ 5600 rpm, with 315 ft-lbf peak torque @ 4000 rpm.
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1. i want to have the motor bored & stroked like my chevy. what’s available?
interesting idea, but there are no big bore kits available, nor can the engine be bored any significant amount. there are only two stroker kits (jun and crower), and these cost in excess of $5000 and only increase the displacement by approximately 10%. this is very expensive horsepower…
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featuresthe engine has an advanced dis type cop (coil on plug) ignition systemwhich is crank and camshaft triggered. no external ignition timing adjustments are available or necessary. all timing adjustment is made electronically by the engine management system (ems) according to internal 3d ignition maps. two knock sensors are provided and timing is retarded by the EMS when knock is sensed.fuel delivery is by a sfi system with both pulse rate and fuel pressure adjusted according to load demand by the engine management system.intake air is measured before the turbochargers by a hot-wire type, mass airflow (maf) meter. this measurement is then compensated for temperature & barometric pressure (altitude) in the engine management system.all systems are controlled by an integrated engine management system consisting of a main engine control module (ecm) and several peripheral electronic control units (ecu) for the ancillary systems.all aforementioned systems are described/discussed in more detail in later sections of this faq.
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1. what spark plugs should i use?
stock vehicles respond very nicely to factory toyota plugs, gapped to toyota specs. of .043″. if you have a tt or single-turbo Supra and run higher than stock boost, or if you notice a high-rpm miss, you may want to consider reducing your plug gaps until the miss goes away. there is still debate about whether to switch to another plug at bpu levels, but single-turbo supras will probably benefit from a plug one heat range cooler than stock. many bpu owners have switched to plugs one heat range cooler than stock also such as NGK 3330, 1095, 6097, and 1283. these four are described below.
to begin with…stock plugs on the supra are the NGK BKR6EP-11, which is defined as:BKR6EP-11: B = thread diameter of 14mm, K = construction type: hex size 5/8″ w/ ISO projection tip, R = resistor type plug, 6 = heat range #6, E = 19mm (3/4″) thread reach, P = platinum-type plug, -11 = x/10 – 1.1mm pre-gap (0.044″)now keeping that in mind, (in what the car calls for, and specs it requires) now lets compare the BCPR7ES(-11) 1095/3330 and the BKR7E(-11) 1283/6097 plugs:(1095) BCPR7ES-11: B = thread diameter of 14mm, CP = hex size 5/8″ w/ projected insulator (which is out-of-spec), R = resistor, 7 = heat range #7, ES = standard 3/4″ thread reach w/ 2.5mm diameter center electrode (which is prone to misfires), -11 = x/10 – 1.1mm pre-gap (0.044″)3330 is simply the BCPR7ES w/out the 1.1mm pregap (therefore gapped at 0.0315″)(1283) BKR7E-11: B = thread diameter of 14mm, K = construction type: hex size 5/8″ w/ ISO projection tip, R = resistor type plug, 7 = heat range #7, E (stand-alone digit) = v-grooved center electrode w/ 1.5mm diameter electrode.

6097 is also the BKR7E w/out the 1.1mm pregap (0.0315″)

the 1283/6097 (BKRxE) plugs are pretty much the same specs as stock, but one heat range Colder, as well as non-platinum in a copper-core form. the center electrode, as compared to the 1095/3330 is also 1mm smaller in diameter as well as have a v-groove. the smaller the diameter of the center electrode, the better the spark flow. (less chances of misfire) think of the spark traveling through the center electrode as a water traveling through a small/steady stream, as opposed to some wide stream w/ wild rapids and uncontrollable tides. the v-groove also furthermore helps the spark by directing the sparks toward the edges of the electrode, closer to the a/f mixture for the best ignition possible.

if you ever have the chance, try laying down a oem-spec plug… along side with the 1095/3330, and you’ll notice the physical difference. although they “may” work, it is not the correct plug for the car. the BKR-construction plugs are the way to go on the supras (and not the BCP-construction plugs, which are designed more towards Hondas which require a longer insulator), and brian weaver at ngk tech will also agree with me.

the main reason people on this list use 1095’s (and also 3330’s) is that they are more readily available to the public. many napas, and even pep boys stock them and can also get a hold of them if necessary. the 1283 and 6097’s on the other hand, wont even show up on many stores’ ngk parts list! the only means of obtaining these plugs would be through NGK directly, or by calling their main distributor (monarch) at: 888-800-9629 (outside california) or 909-672-8501 (within california).

now that you’ve read all about those plugs, you might also want to try denso iridiums. they are pretty expensive, though. but they are also a platinum tipped plug and won’t need changing every 3k-6k miles. they seem to work well for many in both bpu and higher hp applications.
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2. i’m using stock plugs, and my car isn’t running quite right.
one of the reasons that stock plugs sometimes do not respond well to the added cylinder temperatures created under higher boost conditions is the fact that the plugs were designed to run with longer spark plug noses and longer ground strap. a longer ground strap dissipates heat slower and therefore can contribute to detonation. typically the missing that many experience on higher boost is not because of the heat range of the plug, but because the gap is too wide. it should be noted that denso and ngk plugs such as those supplied with oem cars are designed to operate with a specific gap width (or length), and not smaller gaps. you may need to reduce the gap on your stock plugs or switch to a colder plug. see question 1 above for a list of ngk plugs people have had success with.
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3.i want to replace the spark plugs on my supra tt. what are the steps?

  1. buy 6 new spark plugs from toyota (toyota part number # 90919-01178) or by choosing from section 1 above. also buy 2 crankcase hoses, toyota part number 12263-46010 & 12264-46010 (if needed)
  2. with allen wrench (5mm) remove top cover of engine,10 screws.
  3. remove the two crankcase vent hoses that run between the valve covers.
  4. using small screwdriver, release the wiring harness clips.
  5. unbolt the ignition coils (coil packs). there is a 10mm bolt on each side. there are 3 coil packs.
  6. disconnect wiring from the coil packs. two connectors per pack.
  7. lift out coil pack.
  8. use deep well 5/8th socket to remove plugs.
  9. gap (if needed) and install the new plugs (torque it to 13 ft/lbs). stock plug gap is .043 or 1.1mm, for bpu try stock gap or a lower setting like .035 if your engine is missing.
  10. install coil packs… make sure you have a good seal on the plug.
  11. connect wiring and re-clip wiring harness(2) to clip. make sure each harness routes *below* the crankcase vent.
  12. install crankcase hoses that you bought (or previous ones if they are not cracked).
  13. re-install cover.

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4. how can i read my sparkplugs?
this is covered in the tech section. click here to go directly there.
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5. the engine misses at high boost.
try re-gapping original plugs or new plugs at .026″-.035″. start high and work your way down until it stops missing.
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6. how do i check the engine trouble codes?
for cars with obd1 (93.5 – 95)
turn the ignition switch on. connect a wire between te1 and e1 in the diagnostic connector. supras have two diagnostic ports. one inside the car under the dash (driver side), and one under the hood. if everything is okay the light will flash on and off steadily. if there is a problem it will flash in a sequence that will decipher to a number that relates to a specific fault. for more information about reading these codes click here.
for cars with odb2 (96 – 98)
use an obd2 scanner to read the code. the connector is located under the dash by the left knee of the driver.
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cylinder head & valvetrainthe cylinder head is a single casting of aluminum alloy with two camshaft/valve covers and a central coil/plug cover. combustion chambers are pentroof design with valves angled at 45 degrees away from each other. the spark plugs are mounted near the centers of the chambers.both intake and exhaust valves are made of tempered steel with nitrided stems and valve faces which have been bonded with cobalt alloy for good wear. the valves run in replaceable guide bushings and have replaceable stem seals. single valve springs are employed which are held in place by split keepers and steel retainers, steel spring seats are also provided. valve lash adjustment is by “bucket and shim” type lifters fitted between the valve stems and camshafts. the intake valves are 33.5mm (1.32″) in diameter and are lifted 8.25mm (0.325″) by their camshaft. exhaust valves are 29.0mm (1.14″) in diameter and are lifted 8.40mm (0.331″) by their camshaft.the intake camshaft is fitted with special timing lobes for the dis ignition and sfi systems. the intake camshaft opens the valves 3 degrees btdc and closes them 50 degrees abdc. the exhaust camshaft opens its valves 52 degrees bbdc and closes them 4 degrees atdc. each camshaft is held in place by seven heat-treated, unbushed bearing caps.
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1. what does dis mean? is it an abbreviation for distributor?
dis is an acronym for “direct ignition system” and generally means a distributorless, crank triggered ignition.
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2. how about sfi?
sequential fuel injection. some electronic fuel injection systems called mfi cut corners by injecting into multiple cylinders (3 groups of 2 cylinders) simultaneously – the mkiii supra used such a system. the mkiv supra on the other hand, “can” control fuel into each cylinder individually.

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3. how can i do a cylinder leak-down (clt) test?

  • basically, a cylinder leak-down test consists of pressurizing a cylinder with shop air and listening for leaks. fashion an adapter from an old sparkplug so you can hook up an air hose from your air compressor. rotate the engine until the cylinder to be tested is at tdc compression. be sure to get it exactly on tdc. next slowly turn up the air pressure regulator on your air compressor or slowly open the supply valve to pressurize the cylinder. go slow because the engine may try to spin – keep hands and tools clear of belts, etc. once the cylinder is fully pressurized listen for air leaks. do not confuse a “seashell” sound for a leak. air leaks will be very distinct sound and you may even feel a rush of air. open the throttle and put your ear next to the intake opening. a rush of air indicates a leaking intake valve (bent valve? misadjusted or sticking?). next put your ear to the tailpipe opening, air rushing out means a leaking exhaust valve (bent, misadjusted, sticking, or burnt?). listen at the oil filler cap. you will hear a slight hiss of air. this is normal ‘blow-by’ leakage. how much is normal? well, many clt tools have a flow meter to measure how much air is coming by the piston rings and out thru the oil filler cap. usually less than 15%. you probably don’t have an air flow meter to hook in-line with your air hose, so instead try to remember what each cylinder sounded like and compare them to one another. engines with good compression and good rings will sound even, slightly louder than a ‘seashell’ and you will not feel any air rush. lastly, take the radiator cap off and look for bubbles. bubbles indicate a blown head gasket or maybe a cracked cylinder head. doing a clt along with a compression test will tell you a lot about an engine’s condition.
  • leak down test by dennis haynes

    a number of people have asked “What is a LEAK DOWN test?” and “Can I do it myself?”. first, let me explain the concept. we already use a compression test to determine an engines condition. The problem with this test is that there are too many variables. it can only be used to check engine condition by comparing cylinders to each other or a past norm. variables such as cam profile, engine cranking speed etc, will affect the readings.

    a leak down tester uses air from a compressor and measures the rate at which it leaks through the engine. this is done with the engine not running and the beauty of this is that toy can find the source of the leakage by listening for the escaped air. internal leakage is found by air bubbles in the cooling system. tools need are a leak down tester and an air compressor. the tester is available from Milton at about $60.00. compressor should be at least 2hp and deliver 90psi.

    procedure: remove spark plugs. set engine to tdc #1. calibrate test gauge per the instructions. Lock engine so it can not turn. connect hose to spark plug hole. connect pressurized gauge to hose connection. read leakage. if looking for coolant leaks and nothing obvious shows up, bypass gauge and connect shop air direct to cylinder. open radiator cap before this. if coolant sprays out, you have a head problem. do same test on rest of cylinders. remember to set tdc of each piston for compression stroke. this test is also great for air cooled head leaks and valve problems. note that all engines will have some leakage past the rings. i always do full pressure test when i suspect a problem. make sure engine is secured with full pressure test. it will spin violently. with gauge connected, you can rock crankshaft to see if leakage changes. if so, this is a sign that the ring lands are wearing, new engines will also do this until the rings are seated.

    i know these instructions are kind of flaky, but I hope this gives some insight as to this type of test. if having a mechanic work on your vehicle, he should be familiar with the leak down test. i would be concerned if he isn’t. this is a basic troubleshooting tool that all fleets use. especially on diesels.

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blockthe cylinder block is a single iron casting without lined cylinders. it has seven massive main journals with two bolt main caps. accessory bosses have been cast into the block to allow direct mounting of the alternator, starter, A/C compressor, and other accessories. with only minor machining differences, both the GE and GTE engines share a common block casting.
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1. i thought the supra was a high performance engine. why doesn’t it have four bolt mains like a camaro?
first reason is that the main journals in the 2jz engine are absolutely massive. they are some of the biggest mains you’ll ever see in an automotive engine, so block flex is not an issue as it is with domestic blocks. second reason is that the 2jz crankshaft is already a precision balanced component with twelve counterweights. as such, it does not require extra restraint or externally balancers. third reason is that with the inline configuration of this engine there are seven main journals taking the load, not just five as there are with domestic v-8 engines. in summary, the box stock lower end of the 2jz engine is nearly indestructible and is capable of delivering well over 900 horsepower reliably to the rest of the powertrain. it was “designed” as a high performance engine, not modified to be one.
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pistons & rods pistons are an aluminum alloy and have two compression rings and one oil control ring. the first compression ring and the oil control ring lands have been nitrided for durability. the second compression ring has been chrome plated and the piston skirt has been resin coated to reduce cylinder abrasion. an oil gallery has been cast into the piston and as oil from the oil jets is sprayed onto the underside of the crown, oil circulates within this gallery and cools the piston.the same forged connecting rods are used in both the ge and gte engines, employing press fit pins with retainers on the small ends and replaceable rod bearings on the crank end. oil jets are provided on the large end for directing oil onto the underside of the piston crown for better cooling.
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1. are aftermarket forged pistons and rods a good idea?
the sellers of these components think they’re an excellent idea! in reality, the stock supra pistons are as advanced a design as any aftermarket piston, and the rods are already forged. the stock reciprocating assembly “can” hang together just fine up to 8000-8500 rpm (although we’re rev limited to 6900-7200) and can produce insane power levels. however, to be fair to the aftermarket, there are some weight savings and strength increases to be gained with aftermarket rods and pistons, but these become advantageous only when the engine is being prepped as a full race engine.
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crankshaft & torsional damper the forged steel crankshaft incorporates twelve counterweights and seven main journals; the main and rod journals are induction hardened. replaceable aluminum alloy main bearings are used.a dual mode torsional damper is fitted to the front of the crankshaft. this is NOT an external balancer, as the crankshaft is fully balanced, rather it dampens both the axial twisting couples produced by the firing pulses, and the radial bending moment from the accessory drive belt.
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1. can I pull the harmonic balancer off, replace it with an underdrive pulley and pick up 10-15 horsepower?
first, it’s not a “harmonic balancer”. it’s a torsional damper. second, it is NOT a good idea to replace it with a solid underdrive pulley.
torsional analysis of a reciprocating engine is an extremely complex, computerised study and design of a system to smoothly and safely transfer 20,000 explosions per minute into useable torque without destroying the engine or drivetrain. oh, and do it for the life of the car. without exception, every reciprocating engine, pump, or compressor can benefit from torsional damping, but getting it right is an extremely complex process, and the consequences of getting it wrong are broken crankshafts and/or ruined drivetrain components. so in summary, this is NOT a good area to try to pick up cheap horsepower on the supra unless you are prepping a full race engine and plan to rebuild the engine and drivetrain on a semi-regular basis.
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lubrication systemthe engine lubrication system consists of a wet sump, pressurized system with a crankshaft driven gear type pump, spin-on oil filter, and a water jacketed lube oil cooler which is built into the oil filter adaptor housing. the engine oil pan is actually two pans, an upper and lower unit, neither of which can be easily removed without either lifting the engine from its mounts, or removing it entirely from the car. there are dual oil supply galleries in the engine which supply the cylinder head, crankshaft, piston oil jets, and the turbochargers with pressurized oil. pressure relief valves are fitted to the oil pump, filter and oil cooler. if oil pressure at the discharge of the pump is too high, its pressure relief will open and relieve pressure back to the suction side of the pump. if either the oil filter or the oil cooler become plugged, their pressure relief valves will open and allow oil to bypass around them. in this way, the system is both protected against overly high pressure, and oil flow is always assured to the main gallery.
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1. which type/brand of oil and filter should i use for the mkiv tt engine?
turbocharged car owners generally favor pure synthetic or synthetic blend oils over dino oils. synthetics’ shear and anticoking properties at high temperatures are ideal for protecting turbocharged engines. any synthetic of the proper weight will do. don’t get hung up on brand names. if your tt has a new engine or fresh short block, allow 5,000 miles for break-in with dinosaur (mineral) oil before changing over to synthetic oil. the “dino oil” helps seat rings, seals, etc. generally stick with toyota’s specification of 10w-30. however in cold climates, a change to 5w-30 may be warranted during the winter. be aware if you have a high mileage supra and switch to synthetic, your oil consumption will probably increase. despite synthetics’ other very desirable qualities, some supra owners have found that certain brands of synthetic are not as friendly to valve stem seals as dino oil, and may actually accelerate wear in this area!
toyota make an excellent stock filter for the supra, and an even larger capacity filter is available with the same construction for the land cruiser or lexus, and these are good upgrades for the supra – the toyota p/n for these is 90915-20004. In the aftermarket, Amsoil make a very good filter, as do k&n. stay away from the bargain store brands that are on sale for only two or three dollars. this is not a good area to save money.
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2. how often should i change my oil?
the critical question that has no hard & fast answer. it just depends…. how often is the car driven, and “how” is it driven? is the engine modified, is the car raced, etc. the best answer is “somewhere” between 2500 miles and 10000 miles per oil change. 2500 miles if the car is raced, and/or does lots of stop & go driving or quick trips to the grocery store, or if you operate the engine in a very hot or dusty climate. if, however, you clock a hundred miles of driving each day at freeway speeds, and the engine is running at normal operating temperatures and NOT at peak output for several hours, extended oil changes are certainly possible with synthetic oil AND regular oil analysis. in summary, frequent oil changes are sometimes seen as a waste of good oil, but they’re a good insurance policy for you and your engine if you don’t have an established oil analysis program and don’t know exactly what’s going on with your oil.
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3. is it difficult to change the oil? how long should it take?
it isn’t difficult, but the first time you do it, set aside a couple of hours to complete the task and be prepared to get messy. after you have done it once or twice, it should only take about 20 minutes and you’ll have figured out how to do it with less mess. while you have the car up on stands, it’s a good opportunity to check over the entire undercarriage and check the torque on the suspension mounting points both front and rear.
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4. what specification and oil weight should i use?
the list members have personal preferences. for fastest turbo spooling and maximum horsepower, stay with the recommended 10w-30. heavier oils can be used, but they will make the engine warm up slower, run hotter, and lose more horsepower to fluid friction. in very cold climates, a switch to the same oil in a lighter range, such as 5w-30 will improve starting in the winter.
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5. aren’t all engine oils basically the same?
no! conventional and synthetic oils are as different as day and night in performance. you can’t beat any pure synthetic with a conventional (mineral) or conventional/synthetic blended oil. the pure synthetic wins, hands down, in any performance comparison except price.
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6. how can i know if my oil is not performing?
the old mechanics’ practice is to wipe the inside of the oil filler cap with a clean rag. if there is a visible brown deposit on the metal surface, they’ll say it’s time for an oil change. this isn’t really a valid test, but no one has ever ruined an engine with too frequent oil changes, where the opposite is certainly true! the best way to know about your oil’s performance is to establish a regular oil analysis program, which involves taking samples of the oil periodically to an oil analysis lab, and they’ll tell you exactly how the oil is performing.
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7. how important is it for my turbos/engine to use the right oil?
superheated oil exiting the turbo bearings sometimes looks like a chocolate mousse. this is why the turbos have a water jacket to help cool them. a turbocharger puts extreme stress on oil, and the oil is the only thing in your engine separating metal-to-metal disaster. again, bargain basement or generic brand oil is not a wise idea.
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8. when to switch to synthetic? what kind?
you can switch to synthetic as soon as break-in of the engine is complete. ordinarily this will be somewhere between 2,000 and 4,000 miles. if you have taken the engine to maximum load (top speed for more than 15 seconds), regardless of mileage, break in is complete. list members have varying experience with mobil 1, sastrol syntec, redline, and amsoil. they are all very good, some have advantages over the others in terms of availability, price, and small performance differences.
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9. what is the best way to change the oil on my mkiv?
to change the oil, first get the engine to normal operating temperature by going for at least a 20-30 minute drive. when you get home, put the car up on ramps or stands, make sure it’s in park or in gear, and the emergency brake is set, open the hood, remove the oil fill cap, and then get underneath and remove the drain plug. it goes without saying that you should anticipate which way the oil is going to pour out and have your drain pan positioned and NOT have your hands, arms or face anywhere near! after the hot oil has drained out, replace the seal washer on the drain plug with a new one and tighten it snugly, but be careful not to overtighten. although the lower pan is steel, it’s also thin. now to remove the filter, for the ’93-’95 models, if you’re removing the filter from underneath, it’s sometimes necessary to remove the suspension strut that attaches to the lower a-arm, and the plate that is mounted just above it. if you’re a contortionist and have small arms and hands and the proper tools, it’s “just” possible to remove the filter from above. next, put some kind of catch towel up underneath the oil filter to catch the oil that is going to spill when you first start to remove the filter. then, using a filter wrench that fits over the end of the filter, remove the old oil filter. if you have some time to spare, it’s usually better to let the engine cool for a half hour or so before you do this to avoid burning your arm with hot engine oil. wipe the filter mounting surface and block sealing surfaces with an oily rag, and spin it on and tighten snugly by hand. now, fill the crankcase with 5 u.s. quarts of oil. start the engine and watch the check lights to make sure you have oil pressure, then check for leaks around the filter. if everything is ok, then check your oil level and adjust it to indicate at least halfway between the f and l marks on the dipstick.
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10. a “quickie lube” place changed my oil and wanted to put in an additive. they said my engine would get 30% better gas mileage and make at least 20% more power.
oil additives are the “snake oil remedies” of the automotive world. many additives are available with very extravagant claims. there are numerous reputable articles available on additive performance, and they are all negative. in short, it is not recommended to add anything to your oil; as competitive as motor oil sales are, if a worthwhile additive were developed and became available, the major oil companies would be scrambling to include it in their products.
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11. where can i learn more about oil?
there are many technical articles on oil available on the web, see the mkiv tech references for some of the better ones.
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12. why does my oil look dirty when i check my oil level?
all automotive motor oil contains detergent and dispersant additives which will hold oil degradation and by-products of fuel combustion in suspension. in short, a dirty oil is doing its job. the oil is designed this way to prevent these contaminants from depositing on engine surfaces where they can cause piston rings to stick and plug oil pump screens. the oil works in conjunction with the filter to remove these contaminants
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13. my front crank seal blew out. why?
neither the root problem nor the solution is known. (the crank seal blows on some cars with stock rev limiters.) but one possible cause/solution that has been theorized and tried is that at higher than stock rev limits, the stock oil pump cannot relieve enough pressure as it spins faster. as a result, oil pressure rises too much and blows out the seal. modification to the stock oil pump is required to ensure that it won’t happen again.
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cooling systemthe engine uses a sealed and pressurized, forced circulation cooling system, consisting of a belt driven pump, radiator and a cooling fan which is fluid coupled to the pump. coolant temperature is controlled at the inlet side of the pump by an integral wax element thermostat. the thermostat modulates coolant flow between a bypass line and coolant coming from the bottom tank of the radiator. when the engine is cold, the thermostat blocks the passage from the bottom tank and coolant circulates in a loop through the engine and bypass line only; it does not circulate through the radiator. as the engine warms up and reaches the thermostat temperature, the thermostat opens and allows coolant from the radiator bottom tank to mix with hotter coolant from the bypass line. by modulating between these two lines, the thermostat controls the temperature of the coolant going into the engine. once inside the block, the coolant flow splits and part circulates through the block and the rest goes into the cylinder head and ancillary systems. coolant return from the block splits again and goes into both the heater system, the oil cooler, and thereafter back to the pump suction. coolant return from the cylinder head splits and goes to both the throttle body and the turbochargers, and from there it returns to the pump suction.while the actual flow rates of the pump are not known, adequate flow is provided at all RPMs and normal loads to limit temperature rise out of the engine to an ideal 10-12 degrees F under normal conditions. the stock radiator is adequate for casual driving at stock power output, but at higher engine outputs and/or extended high speed racing in warmer climates, the stock radiator cannot cope with the increased load and should be upgraded.
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1. how do i know if my coolant needs changing?
use a voltmeter, and attach the ground lead to the battery negative or the engine. then put the positive lead in the coolant at the radiator cap. it should measure less than 0.500 vdc, and ideally should be 0.100 vdc. more than 0.500 vdc is very bad and the coolant should be changed immediately.
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2. which coolant should i use?
toyota’s red coolant is best, in a mix that is proper for your climate. “green” coolant usually has silicate additives which were formerly promoted as helping cooling efficiency. this is not so, and these additives will reduce cooling efficiency in our engine, and in extreme cases may plug small coolant passages. only use toyota’s red, or other reputable ethylene glycol coolant “without” silicates or other additives.
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3. what’s the proper mix of coolant and water?
some owners in very mild climates use as little as 15% coolant to 85% distilled water with a bottle of redline’s water wetter to help reduce cylinder head temperatures and provide water pump seal lubrication. water-wetter is highly recommended. it has helped produce measurable increases in gas mileage with reformulated gasoline. reduction of cylinder head temps allows more ignition advance before onset of knock, and more ignition advance is conducive to better fuel economy.
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4. why distilled water?
tap water contains varying amounts of minerals and ions, as well as chlorine and sometimes heavy metals. also the pH of tap water may vary from acidic to very base. the minerals in the water will deposit themselves in the cooling passages of the engine and radiator, and eventually build up and reduce the efficiency of the system. worse than this however, the minerals and ions may react chemically and electrically with the aluminum and copper components in the cooling system, and set up an electrochemical process known as bimetallic corrosion which will actually accelerate the failure of these components. this process can be detected with the voltmeter test described above, and if a voltage higher than 0.500 VDC is detected, a very damaging bimetallic corrosion process is at work eating away your cooling system! distilled and deionized water contains no minerals, heavy metals or chlorine, and has a neutral pH, so it is the best fluid for your system.
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5. why is such a low concentration of coolant recommended? i always thought that a 50/50 mix of coolant and water was the best protection for my cooling system.
maybe it’s the best protection if you want to store or drive your supra safely at -40 degrees fahrenheit, but it’s not the best mix to help your cooling system get rid of the engine’s heat. first, understand that water is absolutely the best heat transfer fluid commonly available – bar none. all other heat transfer fluids can “carry” only fractions of the heat that pure water can. the effectiveness of a fluid’s ability to “carry” heat is called its “specific heat capacity”. for example pure water has a specific heat capacity of 1.0 and pure glycol (coolant) has a specific heat of 0.6. mix them in equal proportions (50/50 mix) and you have a fluid that will perform only about 80% as well as pure water in carrying heat away from the engine to the radiator. a 15/85 mix will perform 94% as well as pure water, or to put it another way, about 14% better than the 50/50 mix.
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6. doh, i didn’t sign up for a course in heat transfer. just tell me the right proportion of coolant and water to put in my system.
okay, here’s just the facts: run the “least” amount of coolant you can in your system that will provide freeze and boil over protection “for your climate”, throw in a bottle of Redline water wetter too, and fill the system the rest of the way with “pure distilled” water. here’s a table that’s pretty accurate so you can pick which proportion will work best for your climate. all figures are in degrees fahrenheit.
% Coolant Freeze Boil20% 16 253
33% 0 256
50% -34 265
70% -90 277back to start
7. what’s the best way to flush & clean the cooling system?
people have had very good luck with the prestone flushing system and there is a tech article about it. you can find it here.
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8. my car seems to run very hot in the TX or AZ summer and gets terrible gas mileage. should i try a lower temperature thermostat?
several members in the warm, humid climates have reported good success switching to the trd 165 degree thermostat.
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9. i think i’ll take the thermostat out altogether. won’t this help cool the engine even more?
no! this will cause the car to warm up erratically, the coolant, and oil temperatures in the engine to vary considerably, and both of these will cause accelerated wear of components such as rings and bearings.
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10. what about electric fans, do they help?
again, the sellers of these fans claim improved performance, however other users think the performance is less than the stock fan system. if they help at all, it appears to be marginal, and then only at idle or low speed cruising.
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11. how ’bout that cool looking trd radiator cap. will that make it cool better, and the car go faster?
actually it might! that radiator cap allows the cooling system to run at a higher pressure, so in theory you could run less coolant and more water without having to worry about boil over. more water means better cooling and more cooling means less timing retardation. also, higher pressures cause smaller bubbles to form in the system thereby causing better heat transfer. so yes you might even go a little faster with that radiator cap! the caveat is that a cooling system running at higher pressure is going to cause more of a strain on the water pump seals, hoses, and radiator.
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12. i live in denver, and in the summertime when i park my car and turn off the engine, i hear gurgling noises. once i even saw steaming coolant coming out of the radiator into the overflow tank. what’s wrong?
several things working here. first, water boils at a lower temperature at higher altitudes. second, our engine and cooling system tends to “heat soak” for a few minutes after shutting off. that is to say the engine is still very hot internally, but since the cooling system is no longer working with the car off, the temperature continues to rise in the system. also, with the engine shutoff, and the water pump no longer circulating the water, there is no pressure in the system. so more heat getting dumped into it, plus less pressure, plus higher altitude will all contribute to coolant boil over.
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13. my car overheats since i installed (pick one or more):
1) a fmic
2) oil cooler
3) electric fans
4) started road racing
5) went bpu+++
what’s wrong?
this is really an apu topic, but it’s a good lead-in to help explain and understand the cooling system. fmic’s and oil coolers that are mounted in front of the radiator degrade the performance of the cooling system. instead of the radiator getting air at ambient temperature, it’s getting it at ambient plus perhaps 30-50 degrees. another way of looking at it, all that heat that the fmic and/or oil cooler are getting rid of, is being picked right back up by the cooling system.
a very important point to understand is that automotive engines are only about 30-35% thermally efficient, which means only a third of the fuel you burn will make useful horsepower, while one third is wasted and gets turned into heat in the cooling system, and the last third is wasted and goes into the exhaust system as heat there also. following onto this point, something that is nearly always overlooked with horsepower raising mods is that for each horsepower gain at the rear wheels, there is at least the same, if not a greater horsepower loss into both the cooling and exhaust systems. so, after you’ve turned the supra from a docile little 300rwhp sports car into an 800rwhp monster, but you’ve done nothing to the stock cooling system, it’s no wonder the car overheats whenever you go for a longer drive than just to the grocery store. you’ve more than doubled the engine output, without doing anything to help the cooling system!last point, there is a big misconception that since the supra’s rated output is 320 BHP, the cooling system is rated to cool the engine OK at 320 bhp. this is not so at all – and not by a long shot! why? well the engine in normal use very rarely sees maximum output, and then only for very short durations. so the toyota engineers (and every other brand of automotive engineers) figured out how much “average” horsepower the car needs to make under normal operating conditions, added some reserve and then used that figure to size the cooling system and radiator. we’ll be shocked to know that this “average” horsepower figure is probably on the order of only 30-50% of the maximum engine output. gm/ford & chrysler engineers used to be notorious for getting this figure wrong and building cars with undersized cooling systems that overheated on a regular basis. so this is why you can take your 600rwhp supra out on a straight flat highway and it’s probably happy at 60-70mph, where the engine is only making 100rwhp or so to maintain 65mph, but you can’t take it road racing without it overheating. to validate this point, you only need to look at the size of the radiators on the large 18 wheelers. these truck engines actually produce less horsepower than a stock supra, but it takes nearly all that horsepower on a continuous basis to keep a big rig going 60-70mph. so their cooling systems must be rated for their maximum horsepower on a continuous basis. because of this, their radiators are typically at least 600-800in2 in frontal area, while ours on the supra is only about a third of that.so what’s the solution?a bigger radiator and/or more/better air flow across it. with a fmic, this is a tough situation, but some road racing list members have come up with innovative solutions for ducting air to the radiator separately from the fmic.
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intake systemthe ge and gte engines share a common air intake system consisting of a high capacity, disposable type panel filter mounted in an air box, with a cool air intake snorkel oriented to the front of the car. the commonality between the ge and gte intake systems ends at the outlet of the air box. For the gte engine, following the air box, air is then metered by a hot wire mass air flow (maf) sensor, then goes to the twin sequential turbocharger system inlet. it is then compressed and thereby heated, and the charge air then goes to an air to air intercooler mounted in the lower front of the car on the passenger side. cooled charge air from the intercooler then is piped to the throttle body, and twin chamber intake plenum, until finally, air flow divides at the intake manifold and goes to the six inlet ports of the head.the <turbochargers> and their <control system>, <intercooler>, and <maf> are all described in greater detail in other sections of this faq.before leaving the intake system, it is useful to note several features of the throttle body. it’s equipped with two butterflies; one is a “sub-throttle” butterfly and it is upstream of the “main” butterfly. although it looks like a choke for cold starting, the sub-throttle butterfly is usually referred to as the “TRAC” butterfly as it is used by this system as a torque limiter when it senses wheel slippage. both butterflies are equipped with position feedback sensors.
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1. what can I do to improve the performance of the intake air system?
lots of things, if you have deep pockets! check out the <bpu> and <apu> sections of this faq for the expensive stuff that can make big differences at higher engine outputs. one cheap mod that works very well and will give you good return for your dollar, is the “drop-in” k&n replacement air filter. just take the stock toyota air filter out, and “drop-in” the k&n replacement. it’s a less restrictive design than the stock unit, and over time as it gets dirty, it “loads up” less than the stock filter. plus, it’s cleanable and reusable so it costs less to maintain. one very important point with the k&n, and other filters similar to it – these are oil-coated filters and it is very important to not overcoat the filter media. why? just downstream of the filter in our supra is the hot wire mass air flow sensor – if oil from an overcoated air filter finds its way onto this sensor, and fouls it, it will start producing erroneous readings and the car will not run well at all. cleaning this sensor is a very dodgy process, and replacing it is expensive. bottom line, be very careful with oil impregnated filters and do not overcoat them.
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exhaust systemthe exhaust system on the 2jz-gte engine consists of a pair of cast steel exhaust manifolds, each serving three cylinders, and a crossover stainless steel balance pipe with bellows which allows for expansion/contraction of the system without warping or cracking. each manifold (three cylinders) feeds one turbocharger. the <turbo’s> and their <control system> are discussed in detail in a later section of this faq.from the single outlet of the turbochargers, the exhaust goes to a downpipe equipped with another bellows for expansion/contraction, and two inline catalytic converters. the cats are monolithic construction, three way type with metallic substrate. from the rear most cat, the exhaust splits into two pipes, then recombines at the muffler which is located at the very rear of the car. the entire system is made of stainless steel.for closed loop control of the air-fuel ratio, and fault sensing of the catalytic converters, the exhaust system is equipped with two lambda sensors. one mounted ahead of the first catalytic converter, the other o2 sensor is just after the 2nd cat. only the 1st o2 sensor provides feedback to the ECU for closed loop fuel trim. apparently the 2nd sensor is used for fault detection of the cats.
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1. i “accidentally” ran some (pick one):
1. leaded gasoline
2. octane booster
3. mysterious fuel additive from a “quickie lube” place through my car thinking it would make it go faster. now it runs terrible and my gas mileage is terrible.
chances are your plugs are fouled which is an easy fix, but more importantly, you may have “poisoned” your lambda (O2) sensors. a single tank of leaded gas is a confirmed O2 sensor kill, and all the other junk that is sold to boost octane, etc. is suspected to shorten their lifetime. these things cost around $115 each from our discounted parts sources and should be replaced any time you have these symptoms. actually, you only need to replace the upper O2 sensor (the one at the top of the downpipe, as it is the one which is used to trim the fuel calculation in the ECU) Be sure to <reset the ECU> after replacing the O2 sensor(s) as this will clear the former fuel trim calculations, and you should be good to go.
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2. my supra emits smoke when i start up. what does the smoke indicate?
if the cloud is relatively blue or blue/black, it may indicate oil being burned along with the fuel. this may be caused by either worn piston rings, worn valve stem seals (very common on older supras – and fixable), or an oil viscosity that is too low. if the cloud is black, it indicates excess fuel being burned. if the cloud is white, it may simply be the moisture in the cold engine and exhaust system being burned off. if there’s a lot of white smoke and it continues for a long time, you may have an internal coolant leak. (*note, mobil 1 synthetic oil burns greyish-white)
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3. my car is (insert modification level here), do i need an egr blockoff plate?
yes! emissions problems aside, every mkiv should have one. it is possible for the egr valve to leak, causing low compression in cylinders 5 and 6. this is a common thing to go wrong, but a very simple thing to fix.
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turbo system
1. how does the ssts (sequential twin-turbo setup) work?
first off, the is no #2 wastegate. there is only one wastegate and it comes off the #1 turbo because that turbo is always on line, therefore you always have a wastegate. there are 4 sets of vsv’s, actuators, and control valves for the sequential turbo system. each vsv is simply a solenoid that is either 100% open or closed, allowing manifold pressure to pressurize the different actuators that open/close the four different valves.
wastegate: when the manifold reaches 11#’s of boost, the ecu sends a signal to the wastegate vsv, that allows manifold pressure to build in the wastegate actuator which opens the wastegate.
exhaust gas bypass valve (ebv): somewhere around 3500 rpm, the ecu sends a signal to the exhaust gas bypass valve vsv, which allows manifold pressure to build in the exhaust gas bypass valve actuator which opens the bypass valve. this is a small opening inside the #2 turbine housing which allows some exhaust gas to go through the turbine of the #2 turbo which makes it start spinning, and dumps the exhaust gas out the exhaust piping coming off of #1 turbo. since it is a small amount of exhaust gas, it pre-spools the turbo and does not get it up to full operating speeds. this will smooth out the transition from 1 to 2 turbos. This valve is similar to a wastegate in design, but is located after the turbine wheel instead of in front of the turbine wheel like a wastegate would be. this is not a wastegate!
exhaust gas control valve (egcv): this valve is located in the exhaust piping downstream of the #2 turbo. when this valve is closed, all exhaust gas must go through the #1 turbine wheel to get out through the rest of the exhaust system. at around 4000 rpm, the ecu sends a signal to the exhaust gas control valve vsv, which allows manifold pressure to build in the exhaust gas control valve actuator which opens the control valve. this allows exhaust gas to go through #2 turbo and out the exhaust system which brings the #2 turbo up to full operating speed.
intake air control valve (iacv): this valve is located in the intake tract coming off of #2 turbo. it is closed below 4000 rpm so that boost pressure coming off of #1 turbo cannot backup through the #2 turbo and back out the air cleaner/suction of #1 turbo. there is also a 1 way reed valve within the same housing of the intake air control valve. as the #2 turbo starts to pre-spin at 3500 rpm, it will build some boost. if it builds enough boost, it will open the 1 way reed valve to allow this boost into the intake tract to join with the discharge boost pressure coming off of #1 turbo. at somewhere over 4000 rpm, the ECU sends a signal to the intake air control valve vsv, which allows manifold pressure to build in the intake air control valve actuator which opens the control valve. this allows the full boost pressure coming off #2 turbo to join in with that coming from #1 turbo and you are now fully on line. Usually, the exhaust gas control valve will open first, which gets the #2 turbo spinning at full rate so that it is building good boost before the intake air control valve opens, allowing this boost to join in with that coming off #1 turbo. if the intake air control valve opens before the exhaust gas control valve, the boost pressure coming off #1 turbo will go backwards through #2 turbo, spinning it backwards if there isn’t sufficient exhaust energy to keep it spinning forward. when the exhaust gas control valve opens, and the #2 turbo has to reverse the direction of the spin. this is a tremendous strain on the turbo shaft and bearings. if the sequential operation is not a well orchestrated symphony of motion, it is easy to see how the #2 can be prone to failure. for an alternate explanation including diagrams, see the new car features section. the appropriate pages are 91-95.
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2. what does a vsv do?
vsv is short for vacuum switching valve. it is just an electronic solenoid, which either opens or closes 100% when energized. this will allow the vsv to either pass boost pressure through it from the actuators (like the wastegate actuator) or block it off.
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3. will a front mount intercooler (fmic) help my bpu car?
probably. the stock intercooler is very good, and keeps charge intake temps near ambient during normal “sprints.” during longer periods, such as road racing or high speed pulls, the intercooler will become heat soaked and intake temps can go to 150F or higher, depending on ambient conditions. cooling wise, a fmic will probably only help during extended runs or high boost. a fmic will flow better than the stock unit, so it will probably make at least a little more power.
the effect of a front mount is most dramatic when the stock intercooler is in bad condition. the stock unit does not take well to any sort of bug or rock, as the fins bend and break easily. by comparison, my spearco laughs at the largest of dragonflies.another issue is oil. Over time, oil thrown out by the pvc system and turbo seals will condense in the intercooler and coat the bottom of it. not only does this reduce intercooler efficiency, but the oil mist is blown into the engine while boosting. oil lowers octane and promotes detonation. i’ve seen 1.5 to 3 degrees more timing advance with an intercooler in good condition compared to an oil-filled one with bent fins. to clean the stock intercooler, use gasoline to get the oil off, and remember to put a breather filter on the PVC hose to the intake, or oil will just get all over it again.
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4. i don’t want to put a big fmic in front of my radiator, can i get an upgraded sidemount?
the only smic i know of is the greddy, which was tested by reg reimer to flow worse than stock. it also has less internal and external fins than stock.
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5. how about upgraded ic piping?
only anecdotal evidence so far, but it doesn’t seem to hurt anything, and it looks trick. might improve boost response because the hard ic pipes won’t balloon out with higher boost.
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6. my ic hoses pop off under high boost. what should I do?
go to napa and order a spring-loaded-t-bolt hose clamp for their cars. the constant tension provided on these units will never allow the hose to pop off again. i have the 3.5 nominal clamp from napa and it was a little too small for the tb, but with a flat blade screw driver and tapping it with a hammer I was able to get it over….get the next size up from nominal in my opinion.
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7. my car won’t boost very high. it stumbles and lets out black smoke while accelerating. what is wrong? i have the stock mass air sensor (maf).
regardless of how bad it looks, it’s a simple thing to fix. air metered by the maf is leaking out somewhere, causing the computer to dump more fuel than is necessary to move the car.
first thing is to check all the hoses and intercooler pipes. make sure each connection is tight, and follow the hose diagram on the underside of your hood to make sure all the smaller hoses are attached correctly. if everything appears to be in good order, you need to do an intake leak test.the primary method of doing an intake leak test is to remove the intercooler hoses to the throttle body and the turbo outlet pipe. plug both ends, pressurize the system and listen for leaks. it helps to splash soapy water on the pipes to spot the leaks.some people perform intake leak tests by plugging the intake and capping off the pcv hose from the exhaust cam cover. if you do it this way, do not be alarmed if a lot of pressure is mysteriously disapearing. some pressure can escape due to valve overlap, especially with aftermarket cam gear(s). if you suspect this is happening, try turning the motor over a little bit and see if it stops.if the stock hose clamps just don’t seem to be working well enough, get t-bolt clamps. you can order them from www.mcmaster.com or buy them from napa (they are listed as heavy duty hose clamps).stock ic’s need 10 clamps (9) 2.75 inch, (1) 3.25 inchfmic’s need more then 10 usually. (1 or 2) 3.25 inch and the rest are all 2.75 inch.
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8. my second turbo doesn’t kick in immediately after i downshift. what is wrong?
its probably the pressure tank. Check to make sure the 1/8” hoses leading to the iacv and egcv have pressure in them. if not, your pressure tank is probably bad.
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9. my boost is acting strangely, and i do not have a boost leak. what could be wrong?
do you really not have a boost leak? an intake leak test is the only way to be sure.
if not, the first thing to check is the hoses. see the hose layout diagram on the underside of your hood? make sure all the hoses listed there are connected properly. the main culprits are the smaller 1/8″ hoses that attach to the intake air control valve and the exhaust gas control valve. some are hard to get to, just remove whatever you need to check them all.if all the hoses are in good shape, then the next thing to check is the solenoid valves (vsv’s) themselves. the vsv for the intake air control valve (iacv) is located near the firewall on the left side of the motor. it’s connected to a 1/8″ vacuum hose which attaches to a hockey puck looking thing (the iacv actuator). when the vsv is not powered, it should not allow air to pass through it. the side attached to the metal mesh of pipes should be blocked, and the side attached to the actuator should vent to the atmosphere.the vsv for the exhaust gas control valve (egcv) should perform exactly the same, but it is harder to get to. it is located directly behind the wastegate vsv, with one 1/8″ hose going straight up and another going straight back.if the vsv’s check out ok, the next thing to check is the pressure tank. the 1/8″ lines leading to each vsv should be pressurized at all times by the pressure tank. if these lines aren’t pressurized when you remove them, its likely the pressure tank is bad.if the pressure tank is ok, next try testing the actuators themselves. apply air pressure to each actuator (the hockey puck looking things attached to the vsv’s, 10 psi should do it) and ensure that they are not leaking and correctly actuate their respective valves. for the iacv, this can be easily seen. the egcv is harder to see, but it can easily be heard if you have an aftermarket exhaust (the exhaust note will get deeper and louder). if the actuator arm on the egcv breaks, the exhaust will rattle excessively (note that some rattle is normal with aftermarket exhausts) and the car will not boost well at low rpms.some people perform the temporary ttc mod to troubleshoot boost problems. if the problem is the iacv vsv, egcv vsv or the pressure tank, the temporary ttc mod will fix the problem.

note that any malfunction of these parts is suspected to lead to sudden second turbo failure, also known as the death whine. if your car produces exactly zero boost when the second turbo is supposed to kick in, has an excessive amount of oil in the intercooler pipes, and makes a sound like this, then you second turbo is probably blown, sorry.

for more information on the supra’s sequential turbocharger system, see pages 88 to 95 of the ncf.
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10. how do i to trouble shoot the sequential system?
as you can see from the discussion in number 1 above, the operation of the sequential system is complicated and requires all it s components to be functioning properly. failure of a component will cause the disrupt the proper sequential operation of the turbos and can lead to failure of one or both of the turbochargers.
if any of these valves aren’t working properly, you’ll have low boost problems:
1. bov (boost will get bled back to intake)
2. ebv (loss of exhaust energy)
3. egcv (loss of exhaust energy)
4. wg (loss of exhaust energy)now if the egcv, or ebv aren’t working properly, you should have strange transition problems, as well as low boost on the low end.if the problem is the wg, you should suffer low boost consistently, whether it’s only #1 or 1+2.one way to sort his out is to put the car into true twin conversion (ttc) as a diagnostic tool. (ttc instructions) if your boost problem goes away with ttc it has to be one of the vsv or actuators that is malfunctioning. ( as an aside many list members feel that ttc is safer for your turbos because by eliminating the sequential operation eliminates the chance that the turbo will boost against a closed valve and twist the shaft).the actuators can be checked in the car. all you need to do is hook up a pressure source (i use a 60cc veterinary syringe) and pressurize the actuator, then watch to see if it leaks down. it’s pretty simple. don’t go over 20 psi with this as you’ll blow an actuator diaphragm or overextend an arm.the vsv’s are the same. hook up pressure to see if they leak. then apply a ground to the wire going to the ecm to actuate the vsv and see if it opens. of course they are not all normally closed, so you may need to check flow just the opposite.

if it’s on the compressor side, it could be your bov passing at low boost. these are easy to check and just need a source of vacuum. there is the suck and blow test… suck on the smaller tubing while a friend blows down the larger tubing. if he can blow through with out resistance it is normal. if he cannot blow through while you are not sucking that is normal operation.

another possible source of the problem is a vacuum leak. the newest of the supras are 4 years old as this is written (jul. 02) the oldest is 9 years old. the various rubber control lines get brittle and leak. the leaks may not be obvious to a superficial look. i suggest replacing them with silicon vacuum hose which has the additional benefit of looking great. short of that if you suspect that is the problem pull the individual hoses to inspect them .
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transmission & differential
1. which transmission is better, the 6-speed or the auto? can either of them handle the additional horsepower?
both transmissions work well, and both can handle 400+hp without a problem. over 400 and you will need to start thinking about getting a built auto. the 6-speed will likely handle pretty much anything you can throw at it.
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2. what fluid should i use in my tt 6-speed? how about in the differential?
we recommend only the stock v160 oil for the 6-speed. it works great. pricey, but not compared to the thousands for a new transmission. do not use redline synthetic d4 atf for the transmission. click here to read why. other brands you may use at your own risk. the redline synthetic 75w90 (not the 75w90ns) in the differential works well.
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3. my 6-speed transmission makes a rattling sound at low speeds – should i worry?
all supra 6-speeds seem to make that sound, which has been likened to shaking a bunch of ball bearings around in a coffee can. it is not a cause for alarm – all the 6-speeds make the sound. it is the flywheel damping springs rattling, not the design of the transmission dogs. if your transmission shifts smoothly and doesn’t pop out of gear, don’t worry about it.
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4. how do i check the torsen differential oil?
there are two plugs on the differential, one is the drain plug and the other is the fill/check plug. the check plug is on the right side just above the drain plug. the hole is a 10 mm hex (allen type). just remove the fill plug to check. if you have a 6 speed and you stick your finger in the hole you will feel the “oil slinger” before you feel the oil. make sure to check the oil level on a leveled surface! according to redline, you don’t need friction modifier for torsen to work, but friction modifier will reduce operating temperature and extend service life of gears.
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5. should i get a lightweight flywheel?
only if you don’t mind the noise. every mkiv with a lightweight flywheel will exhibit transmission rattle with the clutch out. this is noisiest on hot days where the tranny is warm and the a/c is on. it’s only noticeable when engine braking, idling and accelerating at low rpms. make no mistake, it can get VERY loud.
expect to gain about 15 rear-wheel horsepower on a dynojet.
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brakes
1. what minimal brake upgrades will i need for road race tracks?
the most popular choice seems to be hawk blues for the pads and the stock rotors. they stop great, but they will also eat your rotors very quickly. for a more rotor friendly pad that can handle the heat and has almost as good performance, try the carbotech xp/panther plus pads. stay away from cross-drilled rotors. they crack easily if you take them on a road course. motul makes the best brake fluid but is expensive. a less expensive alternative that is almost as good is ford heavy duty truck fluid. last but not least is valvoline synthetic. it is pretty good, inexpensive, readily available and if you change your fluid before track events anyway, it works just as well as the others. stock pads and rotors would be minimal requirement.
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2. i want to remove my rear brake disc but it will not come off, what should i do?
there are two threaded holes on the disc, screw in an 8×1.25 into both holes and keep screwing them in till the disc comes off. make sure you have the emergency brake off!
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suspension
1. what is a good street alignment?
SEE THIS LINK
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2. what is the stock alignment?
SEE THIS LINK
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wheels and tires
1. what kind of tires are the best for sport driving? how about for drag racing?
the generally accepted best street tire for dry track road racing are bfgoodrich g-force t/a kd’s. the generally accepted best street tire for wet track road racing (and very good dry) are bridgestone potenza s-03 pole position’s.
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2. i’m thinking about getting aftermarket wheels. how much do the stock wheels weigh?
a set of 93-97 polished rims were as follows:
fronts: 24.75lbs
rears: 26.55lbs
the 98 polished rims are a bit lighter without the ridges in the centers
fronts: 23.6lbs
rears: 25.4lbsthese are exact weights taken from a mailing center, not a home scale.
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3. what are the names of the wheel parts?
check out thisillustration.
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4. what is offset?
check out this illustration.
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5. what is the size and offset of the stock wheels?
17″ x 8″ (50mm offset) for the fronts
17″ x 9.5″ (50mm offset) for the rears
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n2o – nitrous oxide
1. i run nitrous. what plug should I run?
depends. but you’ll probably have a maximum gap of .030″.
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electrical
1. my airbag light has come on after i opened the dashboard. how do i turn it off?
click here for the fix.
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2. i want to improve the stock stereo. what works?
the supra’s stock stereo is actually pretty good, so be prepared to spend a bit of money to improve it.
front speakers: the most common modification was replacing the stock front speakers. several listers have found that the MB Quart 6.5″ separates (qm218.03cX) can be installed in the door, replacing the stock 4″ midrange speaker there. one lister used 6.5″ Boston Acoustics speakers. either way, you will need to fabricate a new mounting plate to replace the stock enclosure, but this is not difficult. readers who used separates up front generally mounted the tweeters in the door above the stock mids rather than attempting to extract the stock tweeters from their perch.
back speakers: in the back, the stock speakers are often replaced with premium 6.5″ coaxials, such as the mb quart qm160.03kX or boston acoustics, either of which would bolt right in.
subwoofer: the rear subwoofer is a 5×7″ oval, and listers wanting a bit more boom have added 8″ or 10″ subwoofers – sometimes 2,3 or 4 – either removing the spare tire, or building a custom enclosure to the left of the spare. two readers mentioned that a 10″ sub can be mounted directly into the fold-down portion of the rear seat, in a custom enclosure facing backward. listers have used cerwin vega or mtx subwoofers to good effect.
amps: precision power is the most commonly-used brand, with some listers favoring rockford fosgate or mtx. small amps (under 11″ x 8″ x 2.5″) will fit under the passenger seat. larger ones can be installed in the trunk. one lister used a ppi a606.5 mounted just behind the rear seat. some listers used an amp only for the subwoofer, finding the stock amp sufficient for the main speakers. this avoids the need to run rcas from the head unit, as you can just use a good speaker-to-rca converter attached to the stock subwoofer speaker leads.
head units: the stock head unit is a double-din (ddin) size. several manufacturers make ddin units which bolt right into the stock location – many of these are expensive, however, and some listers have installed a normal din unit with a plate to fill in the extra gap. ane lister going the din route used an alpine 7832, and is quite happy with it. readers who bought disk changers mounted them in the glove box or in the trunk.
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3. i have the 7-speaker system in my mkiv, and i want to upgrade the speakers. what fits?
the subwoofer is a 5×7″. the rear seat speakers fit an oversized 6 1/2″. the doors are 4″. and the dash tweeters are small (around 1″). you can modify the door speaker enclosures to fit some 6 1/2″ speakers. list members have had good luck with mb quart speakers, using 218.03cX separates up front and qm 160.03 kx coaxials in the rear. rather than replacing the 5×7″ stock sub, some listers remove the spare tire and put sub boxes in its space.
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4. how do i clear the “check engine” light?
you need to reset your ecu. see the faq entry on the topic for details.
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5. how do i reset my ecu?
unplug the negative battery cable for 1 minute to clear the ecu’s settings, then re-connect it and drive around for a few hours. this will clear the “check engine” light, and your ecu will relearn your car’s mixture settings, allowing you to pass smog if you’ve just reinstalled your cats. alternatively, pull the cover off the fuse box located near the battery. use the fuse pulling tweezers supplied inside fuse box and remove the two green 30a fuses for efi 1&2. after a minute put them back in and the ecu will be reset.
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6. is it possible to swap out 93-96 headlights with the new 97-98 headlights?
it is possible, but the 97-98 do not have the marker lamps in them, other than that they will bolt right in and plug in, if you can do without the clear parking lights then go for it. you can also install the 97-98 marker/turn signal lights on a 93-96. it will take some re-wiring, though.
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7. i want to use a turbo timer, but it seems to interfere with the factory alarm.
when you shut off the car, the doors unlock, just as the doors lock when you start the car – but this works only if you set the alarm with the keyless remote. with turbo timer, you take the key out but the doors do not unlock. get out, shut the door. hit button on key remote and lights will flash twice (flashes only once if you have not turned timer on). hit button again and it flashes once and sets alarm. when the timer shuts off, the doors lock again (you hear it) and alarm stays armed, lights shut off, and antenna goes down if it was up. when you return to your car, hit the keyless remote and lights flash only once causing no unlocking, then hit it again to disarm and unlock. when I first got mine I turned my car off and on in every conceivable way and set alarm numerous times and then tested it each time until I was certain of when it armed and when it locked, etc.
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8. i want to install an aftermarket alarm/keyless entry system and i can’t find the wiring color code for a 93-94′ tt?

name color polarity location
12v [ wht / red ] + ignition harness
starter [ blk / wht ] +
ignition [ blk / yel] +
ignition #2 [ blk / org ] +
accessory [ pnk / blu ] +
lock (arm) [ grn / yel ] passenger kick panel
unlock (disarm) [ wht ]
park lamp [ grn ] + driver kick panel *1
park lamp [ grn ] steering column
door pin [ red / blk ] driver kick panel
trunk goes off with the door trigger
hood pin [ purple / red ] @theft e.c.u. *2
tach wire [ blk ] (no turbo)
[ blk / wht ] (turbo)
at igniter in engine compartment by driver side strut tower
brake sw [ grn / wht ] + plug in left kick panel
horn trigger [ blu / red ] steering column
window[up—-down]driver side [ red / wht —- grn / yel ] **
window [up—-down] pass. side [ red / blu —- grn / wht ] **
*1=bottom of fuse box in white plug
*2=theft e.c.u. and door lock e.c.u. are built together in one module. the module is located high in the passenger kick panel.
**window wires are in the driver side door. wires must be run into the door.

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body
1. i want to keep my supra looking its best. what wax / polish should i use?
zaino bros.
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2. at freeway speeds, my hood vibrates up and down. is there a problem with it opening at higher speeds?
that may be because the drive side hood latch is not engaged when the hood is shut. try placing the flat of your palm near the driver side hood corner (the lower corner made by the head lamp and front bumper) and push down firmly but gently. if you hear a click, that’s the previously unlocked hood latch engaging and locking. to fix, hand-tighten the two rubber bumpers under the hood, click here for a picture. now there’s no chance of the hood popping open at high speeds.
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3. i get a chirping sound from my door. what can i do?
i had enough of my door chirping when closing it and driving with the window half way open. so i decided to do some exploratory surgery – take the door off. well, the inside panel. it is easy with the exception of removing the screw cover from the cup of the door handle. there are 8 screws to remove and 4 plastic “pop-outs”. (look like the plastic thermometers which are stuck in turkey’s, only black) all of these are pretty apparent with the exception of the screw inside the cup of the door handle and the screw inside the cup of the door lever. after you remove the obvious holding the door lever cup in, there is another screw inside that. make note that to remove the first door handle screw, you must first remove the plastic covering. i would not recommend using a screwdriver unless it is bent in the shape of an L. use the bottom of the L to pry up the plastic covering. it doesn’t come off easy (on mine at least). after you have all the screws removed reach under and remove the wiring harness for the windows/locks/speakers. then lift the inside door cover up. immediately you will see the culprit. Metal on metal. the fix: simply place grease on all exposed areas, both the door and the interior panel. i used a teflon grease, but i doubt it matters. there are three primary hooks which you need to ensure you get enough on. that’s it. total time @45min. 20 minutes was spent trying to figure out how to remove the screw covering inside the door handle cup. i hope this helps any of you who are irritated by the door chirp.
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4. does anyone sell a car cover specifically for the mkiv supra that would fit over the wing?
try to get a mkiv Supra cover from the Toyota dealer or one of these links:
www.covercraft.com | www.calcarcover.com | www.performanceproducts.com
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5. my headlights are fogged up inside. what can i do?
you can either replace them or clean/polish them. click here to see how to clean them.
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6. there is a rattle coming from the hatch area. what is it?
your supra probably suffers from the notorious “hatch rattle”.
click here for the fix.
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7. can i get an advice on the care and up keeping of my supra?
click here.

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drag racing
1. what are the basics of drag racing?
click here for drag racing basics.
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2. what’s the best way to launch my tt for a drag race?
with either transmission type, you should deflate the rear tires to 25 psi or less.
auto: powerbrake the car up to about 2000 to 2200 rpm, and when the rear tires begin to spin slowly floor it and get off the brakes.
manual: there are two techniques. one is hard on tires, the other hard on the clutch. the first technique is to floor it in first, then sidestep the clutch at 4,000rpm and let the rear wheels spin long enough to get the second turbo online. the second technique is to rev to 4,500rpm and slip the clutch, keeping the rear wheels from spinning through clutch modulation.
with an auto and drag radials: (the following advice from an experienced drag racer)
first thing to do is to do a good burn out. 5 seconds minimum, but anything over 10 is unnecessary. also don’t do it “in” the water. back into the water and then roll about 2 feet forward and do your burn out there. as there will be some water there when you are about done with the burnout, let go of the brakes and burn out of the hole. this will ensure the tires are dry. as far as tire pressure, take the tires down to about 20 psi and work your way down from there if you spin them too much. like go to 19 then 18 if, I repeat if needed! the higher the psi the less rolling resistance the better the mph. when you are ready to stage you’ll just want to then pull the parking brake up and powerbrake with the brakes as well as high as you can take the rpm’s (so power brake with the regular brakes and parking brakes, this is not recommended with street tires as you’ll definitely get too much boost of the line and smoke the tires too much out of the hole). when the light’s green floor it and let go of the parking brake and regular brakes at once! (this sounds harder than it is.) also make sure to have the car in 1st and shift through the gears manually. shift right at redline, but remember that in 1st the car is revving so hard that you may have to shift a few hundred rpm’s before redline so you don’t hit the rev limiter.
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3. what is a good autocross alignment?
for a baseline, a good autocross alignment for the Supra is:
front: camber: -1.8 (degrees), caster +4.0 (degrees), toe 1/8″ total toe out
rear: camber: -1.8 (degrees), 1/16″ total toe in
for a street/track compromise, modify the above specs by reducing the front toe-out to 1/16″ or even 0. if you run with toe-out you’ll get better turn-in but you’ll wear your tires more quickly. the other settings should be okay for the street. different tires brands and compounds may require different alignment specs to maximize grip. for example Hoosier racing radials require more negative camber than other tires. for the supra, that might mean -2.0 degrees or more. the recommended autocross alignment will decrease the life of your tires! if you want a compromise alignment, try lance’s numbers or modify the autocross alignment by changing front and rear toe to 0 (or just a smidge, 1/32″ out per side, of toe in the front).
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general faq
1. i can’t understand many of the posts – they all contain acronyms i’ve never seen before. help!
for a partial list of the acronyms used on the list click here. after you’ve read the list for a week or two, you’ll pick up on the lingo and no longer have difficulty understanding the posts.
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2. what’s the equation which relates crank horsepower to speed at the end of the 1/4 mile?
hp = (ts/234)^3 * w, where w = the weight of the car with you in it, and ts = trap speed in 1/4 mile.
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3. i’m going to store my supra for some time. how should i prepare it?
fuel system: fill the fuel tank and add stabilizer in appropriate ratio. run engine for a few minutes to ensure stabilized fuel has made it through the entire system.
engine: change the oil & filter and run the engine up to temperature. then put two table spoons of marvel mystery or similar fine lubricant into each cylinder, and crank the engine a few revolutions (don’t start) to coat the cylinder walls and other metal in the upper cylinder with a film of oil.
cooling system: measure the supra coolant mix, if necessary flush the system and add a new coolant 50/50 mixture.
electrical system: disconnect the battery cables, put battery on smart charger.
tires: raise the supra on four jacks to save the tires from getting misshapen.
body: apply two coats of a carnauba-base wax to the Supra body.
exhaust: plug the exhaust end with a shield to prevent anything from entering the motor like humidity or little animals.
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4. there’s no cup holder. where do i put my drink?
many listers have had good luck removing the ashtray and putting their drink in the resulting hole. other suggestions include stuffing 1l bottles between the seat and center console back by the seatbelt latch. also the following link shows a good photo of an aftermarket cup holder: click here
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5. what is the difference between the export mkiv supra and japanese mkiv supra?
click here for the difference. also here is another useful link.
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6. what is horsepower?
measuring maximum engine power, horsepower is the amount of energy required to raise 33,000 pounds one foot in one minute (or 550 pound-feet per second). it is calculated by multiplying the engine’s measured torque by rpm and dividing by 5,252.
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7. where can i get the repair manuals for my mkiv supra?
you can get them straight from toyota. toyota offers 5 repair manuals (vol. i engine, vol. ii chassis/body, electrical systems, automatic transmission- a340e, collision repair). to buy these manuals you will need to call Toyota at 1-800-622-2033 between 7 a.m. and 4:30 p.m. pacific standard time. click here for a list of the repair manuals prices.
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8. where can i get discounts on stock supra parts?
you can get them form jay marks toyota. here is part of jay marks toyota response to our letter:
the discount for sogi/sonic also includes the mkiv owners as well. the parts discount is 10-40%…depending on the part. the average discount offered is 25%. thank you for asking. if you have any questions or need my help…please call anytime.”
jay marks toyota, houston, texas, 1-800-327-2087, 713-943-8930 fax parts@toyotaworld.com
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9. i see some list members have white gauges. where can i get those?
www.nrauto.com | www.rodmillen.com
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10. what is the right way to dyno the supra tt?
before dynoing, it is advisable to let the car rest for at least 1 hour with ice on the engine and the intercooler piping. also reset the ecu*, pull the trac fuse (or unplug the trac ecu), and use high-octane fuel if possible. if you have a stock filter, remove it, and try to dyno on a cool day. the rpm sensor for the dyno will need to connect to a timing wire. if you do not connect this sensor, you will not be able to get a torque reading. the closest wire is located on the driver’s side of the engine compartment in a small, black box. click herefor a diagram. once the car is strapped on, spray the intercooler with ice water/alcohol mixture throughout the entire run if possible. leave the ice on the engine and intercooler piping as well. if the shop has a fan, direct it towards the intercooler. the reason we take these additional cooling steps is to approximate “real world” conditions. the temperature of the intercooler has great bearing on the horsepower the Supra will produce. by taking these extra steps we are simulating the cooling effects of high velocity, cool air, flowing across the intercooler that would be present in normal driving conditions. once the car is situated on the rollers properly, slowly run the engine through the first 3 gears with out bringing the 2nd turbo online. in 4th gear bring the car slowly to 2000 RPMs and then hammer it to redline! in an automatic you want to disable o/d, bring the car to 2000RPMs in 3rd gear, and floor it to redline.
*some members have reported that resetting their ecu’s has also caused their electronic boost controllers to lose their stored boost setting. this is most common with the apexi avc-r.
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11. what are the production numbers for the mkiv supra?
1. click here.
2. the following production numbers* are for the tt and na:

year number produced
1993.5 2,887
1994 3,405
1995 2,266
1996 852
1997 1,379
1998 1,232
total 12,021

*sport compact car magazine, “farewell to the supra”.
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12. i need help with my toyota warranty, what should i do to make the process go smoothly?
to get warranty:

  1. remove all aftermarket parts
  2. reset ecu by pulling efi fuse(s)
  3. change plugs back to factory nd’s gapped at the factory specification (at least two have been denied warranty on plugs alone).
  4. if you have race fuel or additive in tank, drain tank or if car is drivable, run remainder out and refill with 92+ octane fuel (at least one individual was denied warranty for funny gas)
  5. act like a total dummy when getting warranty coverage. for example: tranny: i woke up, got in the car and noticed that i could not shift from 2nd to 3rd gear as if something was stuck, then have a blank look on your face. engine: sure i was running the car kinda hard (5000 rpm) it is a sports car right? when i shut it off after waiting a few minutes for the oil to cool as manual says, it sounded kinda funny, so I took it right to you guys.

also, click here for advice from two of our members, after one of them had trouble with his supra.
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13. how much does the supra weigh? and what’s the weight distribution?

Coupe Sport Roof
5 Speed Automatic
Kg Pounds Kg Pounds
Front 758 1671 767 1691
Rear 701 1545 710 1565
Total 1459 3217 1477 3256
Weight Front Rear Front Rear
Distribution 52% 48% 52% 48%
5 Speed Automatic
Kg Pounds Kg Pounds
771 1700 780 1720
714 1574 723 1594
1485 3274 1503 3314
Front Rear Front Rear
52% 48% 52% 48%
Turbo Coupe Turbo Sport Roof
6 Speed Automatic
Kg Pounds Kg Pounds
Front 841 1854 855 1885
Rear 708 1561 712 1570
Total 1549 3415 1567 3455
Weight Front Rear Front Rear
Distribution 54% 46% 55% 45%
6 Speed Automatic
Kg Pounds Kg Pounds
855 1885 855 1885
721 1590 726 1601
1576 3474 1581 3486
Front Rear Front Rear
54% 46% 54% 46%

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14. i understand some years only came with automatics. which ones?
for turbo models, ’96 was available only with an automatic transmission. all the rest were available with manuals.
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15. is any year supra more desirable than others?
not really. 93-95 are more desirable to some because their obd1 ecus are more friendly to ecu upgrades. 96-98 obd2 ecus can be quite useful in logging obd2 engine parameters and more useful error codes although they generate errors if the cats are removed unless an o2 sensor simulator circuit is installed. other than that, there are only minor differences between the model years.
16. how hard is it to convert an auto supra to a 6 speed?
pretty hard. most agree that it’s much easier to just start with a 6 speed, but if you just can’t find one and have to have a manual, there is a long list of expensive parts you will need. cost will range from about $5000 to $10,000 for parts depending on if you buy all new or try to find used. then add labor…
17. are there any common problems to look out for when shopping for a supra?
not really. just do the standard checks. look for collision damage. make sure you do a compression test on the engine. does the car feel strong? there aren’t really any major problem areas. this is a toyota after all…

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