hey guys

how much power are you getting out of your 3.5" dp´s? and when is it nesassary to step up to 4"?

thanks

 

Dont you mean the 3" downpipe & exhaust? (I think Buschur has a 3.5" but its not very common)

From what ive seen, the 4" exhaust are for those rare builds that are north of approx 800whp (DynoJet)

 

3" downpipe is fine for all of it on a 6466, which is around 900whp on a dynojet

 

im at 700hp right now on an 3.5" dp and im expieriencing tha same problems with heat and backpressure as i did with the 3" and 450hp. and im about to get an g35-1050 for christmas from my cat and dog. so im trying to be prepaired. im not even sure that an 4" dp would fit

 

Are you running a high flow CAT & resonators down stream?

 

yes a 100cell cat and 2 mufflers to keep it a sort of quit

 

I’m gonna guess at your power level, if you’re suspecting an exhaust restriction it’s going to be the cat. Resonators and piping are all straight through. The cat, is not.

 

I have two cars making close to 900whp with a 3" downpipe, and 3.5" cat backs with Precision Gen2 6466 turbocharger.

The cat and probably the mufflers are likely your problem, not the downpipe. The entire exhaust needs to be 3.5" as well. Make sure the mufflers are truly 3.5" or 4" ID with no restrictions.

 

700hp@wheels on my GTR, the 3.5" 100cpi CAT lost 10hp vs open dump before the cat

 

Let me provide additional clarity, while the overall hp loss on the topend running through the cat was ~10hp, there was a substantial loss in torque upon the initial torque hit corresponding to full boost. I suspect the cat disrupts the flow until and creates back pressure until flow through the cat is stabilized.