Exhaust Bypass Valve Mod
Warning: This mod can cause problems with your second turbo. Besides putting more stress on your first turbo, it dampens the normal prespool associated with proper ebv operation. This can lead to the #2 being "slam started" from a stationary position. Please use caution when doing this mod. Reducing the flow between the T's is a smart idea if your dead set on more low end boost.
The EBV (Exhaust Bypass Valve) mod is pretty basic. Doing the mod simply gets more PSI from turbo #1 before the cut-over to turbo #2. What you are doing is slowing the opening of the exhaust bypass valve (ebv)by diverting some of the turbo pressure away from the VSV. The ebv really acts as a wastegate for the #1 turbo and the ebv mod is essentially the same thing as the bleeder T mod(or hose pull mod) for the #2 turbo.
You need to use your discretion when doing this mod, because it may be harmful to the #2 turbo. This mod somewhat eliminates the #2 turbo prespool. Without prespool, when the exhaust gas control valve opens, the #2 turbo isn't moving so it gets "kick-started" pretty fast by a big rush of pressure.
First step is to remove the A and B hoses(Fig. 1), save all your stock hoses!, and use regular 1/4" vacuum hose in it's place. Now cut A and B in half (new A and B hoses). Insert a vacuum T(Fig.2) or Y(Y is used in the photo) in line with hose A and B . Each vacuum T will have an open end bleeding pressure into the atmosphere. Now take another piece of hose (about 5" long) and connect the tops of the 2 T's. That's it!.
As you will notice in Fig. 4, there is an adjustable valve in the bypass line so you can enable or disable the modification. With this mod you should notice an immediate improvement in low end response.
Fig. 1
Fig. 2
Fig. 3
Fig. 4
