Yes and like you said the increased airflow is because of the large exhaust.

 

boost creep comes from a well flowing exhaust and turbo that can move lots of air with a restrictive o2 sensor housing. if the wastegate cant let enough air out of it (as is the case with a stock or unported wastegate/o2 sensor housing on a hybrid turbo, etc then the air it cant let out has to go somewhere and ends up going through the turbine creating more boost.....not the fact that the exhaust is too large. what you needed to do in that situation is upgrade your o2 sensor housing to a larger one or just porting it out. i know this can happen on 14b's with bolt on 1g's, and is remedied by porting the stock o2 housing and taking some material out from behind the wastegate flapper arm...

 

Yeah, the point that I was trying to get across was that the increased exhaust flow can cause the wastegate not to be able to divert enough air to control the boost. I wasnt trying to say that the exhaust itself is what causes the the creep. And yes I completely eliminated my problem, I had a 2.5" tubular O2 housing built for me and I also installed a 34mm wastegate flapper, ported the wastegate opening, and removed material behind the flapper so it opens more.

 

yeah nice. are you on a 14b or 16g?

 

im on a big 16g right now.

 

think it was a worthwhile investment or would you have gone bigger/smaller if you could do it over again?

 

Yeah, I like it alot. Its a great street turbo, fast spool, hella midrange, but it does start to die down a little bit in the highend. I got it about a year ago when my stock turbo took a dump on me, and I wanted something that I could run no problem with the mods I had at the time and give me a nice boost in power. It has done what I intended it to do, it got me into the 12's on a completely bone stock motor from throttle body to oil pan. But yeah I am going to get rid of it this spring for something with a whole lot more topend.

 

damn i figured that turbo would pull right to redline...

 

on a turbo system some back pressure is needed to build pressure in the exhaust housing to turn the turbine. But this would most likley be a problem if you had a really large turbo. A t3t4 is not going to give you a problem for you with 3 inch exhaust and down pipe.I have a t3t4 with a 57trim compressor and 63 a/r on the exhaust and i have a 3 inch exhaust on my civic
that comes out at my front bumper hell my whole ex. is only 11 inches long my sh*t spools fast and sounds like a beast.

 

No, you do not need, nor want, any backpressure. The pressure in the exhaust manifold is the sum of what the back pressure the turbine and the exhaust creates. The pressure difference from before and after the turbine is the exhaust manifold pressure minus exhaust backpressure. So say you have 30 psi in the exhaust manifold, and 10 in the exhaust, the pressure difference here is 20 psi. Lets say we take off the exhaust, so there is 0 pressure after the turbine. That will drop the exhaust manifold pressure to 20 psi, and now the pressure difference is 20 psi. The same! The difference now is that the exhaust manifold only has 20 psi in it, instead of 30. The engine will work much better with 10 less psi of backpressure to deal with. Pumping losses goes down, VE goes up, and power goes up.

-Mike