Engine - 2jz-gte and 2jz-ge

 

General Description

the 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 waterjacketed 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.

 

Questions

 

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.

 

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.

 

 

Specifications

bore & 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.

 

Questions

 

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, and 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....

 

 

Features

the engine has an advanced DIS type COP (coil on plug) <ignition system> which 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 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.

 

 

Cylinder Head and Valvetrain

the 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.

 

Questions

 

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.

 

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.

 

 

Block

the 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.

 

Questions

 

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.

 

 

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.

 

Questions

 

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.

 

 

Crankshaft & Torsional Damper

the 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.

 

Questions

 

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.

 

Lubrication System

the engine lubrication system consists of a wet sump, pressurised 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 pressurised 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.

 

Questions

 

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.

 

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.

 

 

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. after you have done it once or twice, it should only take about 20 minutes. 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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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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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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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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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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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, castrol syntec, red line, 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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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 checklights 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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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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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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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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Cooling System

the engine uses a sealed and pressurised, 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.

 

Questions

 

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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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.

 

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 red line'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 gasolines. 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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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.

 

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.

 

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.

ok, here's just the facts: run the "least" amount of coolant you can in your system that will provide freeze and boilover 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    Boil

            20%          16       253

            33%           0       256

            50%         -34       265

            70%         -90       277

 

 

what's the best way to flush & clean the cooling system?

mohd has had very good luck with the prestone flushing system and has written a tech article about it. you can find it <here>

 

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.

 

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.

 

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.

 

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 boilover. more water means better cooling and more cooling means less timing retardation - 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.

 

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.

 

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 roadracing 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 roadracing list members have come up with <innovative solutions> for ducting air to the radiator separately from the fmic.

 

 

Intake & Exhaust

 

Intake System

the ge and gte engine 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.

 

Questions

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.

 

Exhaust System

the 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.

 

Questions

 

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.