I want to replace my stock exhaust system as i don't feel too much power gain from my T3/T4B even not on 5-7psi. What diameter do you recommend for my Civic VTi? (B16A2) I want to have a custom made one. My idea is:

-55mm (2 1/4") diameter from downpipe to back. May be 60mm (2 1/2") in case the exhaust fabrik has no 55mm in stock.
- simple tube instead of catalysator.
- middle and back exhaust (as silent as possible).

BTW, why do you think the boost pressure drops on higher rpms (6000-) from 7psi to 4psi? No leakings anywhere, i have checked it. I was told it can caused by the too closed exhaused system, too....or too old spring in actuator and that can not hold pressure.

Peter

 

Use a 2.5in. from your cat-back and keep your resonator.

 

Could be caused from bad placement of your vac line to your manifold. Closer the better. Tighten your wastegate. Get bigger exhaust. We did all this to my friend crx and he went home from the dyno with 230hp at the wheels. He was at 180. I think though that the wastegate was te biggest problem. Try that first then the others.

 

I use internal wastegate with actuator. And the actuator is set by the rod length, no vacuum is connected to it. But i will try to use a MBC and it may solves this problem as i keep the rod length set at 7spi, i set the MBC 7psi and in case the pressure drops the MBC 7psi get in action. Or do i think wrong?

Thanks. Then i go for a 2 1/2 system.