skool u

I know that there are gains to be had when going to a 3" downpipe and exhaust but first of all what have people experienced going from a 2.5" to a 3" exhaust and turbo back exhaust?

Also, I'm currently running a 2.5" turbo back exhaust, no cat or resonators and I'm wondering, if the exit diameter from the turbine housing is 2.5" and you swap in a 3" exhaust around where the piping straigtens out under the car, how much would you gain as opposed to putting a 3" downpipe right off of the turbine housing and going 3" the entire way out? It's a good 2 feet or so piping isn't it?

spectacle

How much power are you making now and what are you looking for?

skool u

I made 330 on a mustang dyno and I'm essentially using something very similar to the Drag kit. I'm running a straight 2.5" turbo back exhaust; however, I think the piping I ended up using for under the car was a 2.5" O.D. so it's probably a bit more narrow than a straight 2.5" exhaust.

I'm not looking for major gains, I'm pretty content with what I have but I would like to try and flatten out the boost spike in the lower gears which my tuner said might be because of the log manny and 2.5" piping.

spectacle

At that power level, the extra effort needed to get what you doesn't seem like it would be worth it.

Your boost spike sounds more boost controller related. What boost controller are you using?

skool u

I'm using a manual turbosmart one but it's cranked wide opened and it should just be free flowing, I might as well take it out. I'm not too concerned with the spike because afr's still show at a good level.

I'm also just wondering about the diameter because a good friend turbo'd his lude and said he got about 40 or so whp from going to a 3" turbo back exhaust. Not too sure about the validity behind it but I don't have much reason to doubt him. He was running a similar turbo (t3t04e) and it was on the h22a4 engine.

o'malley_808

I had a log style (Ultimate Racing) turbo system with the stock exhaust and 370whp. I didn't have any boost spikes so your exhaust is definately not the problem. Post up how you have your vacuum lines run for the wastegate. I would definately ditch the manual boost controller. My guess is you are running a vacuum source off the intake manifold also rather than the turbo.