What Size exhaust 4" or 5" ?

onebadf150 · May 2, 2013

I think that 4" is the way I'm going with the addition of SDP 4" down pipe all black ceramic coated.

CATDiezel · May 2, 2013

Rowdy said:
Yep 4" exhaust is the BEST wished I would have got 4"! :thumbup:

Glad you came around....

5" looks proportional on these trucks with any kind of tire size upgrade though....

Powell · May 3, 2013

If you don't plan on upgrading the turbo other than a deeper tone it's down to how you want the exhaust to look. I have a 4" setup that I just RECENTLY added the muffler delete kit to. I barely noticed any difference in sound. In the cab you hear the bypass/blow off or whatever it's called on these trucks. It's been the exact same since I went with the 4" delete.

Anyone who wants to argue that you can max out a 4" for flow on a straight pipe with a stock turbo or any bolt on turbo has drank way to much kool aid... ROFL!

onebadf150 · May 4, 2013

Powell said:
Anyone who wants to argue that you can max out a 4" for flow on a straight pipe with a stock turbo or any bolt on turbo has drank way to much kool aid... ROFL!

Lol

Rowdy · May 4, 2013

Powell said:
If you don't plan on upgrading the turbo other than a deeper tone it's down to how you want the exhaust to look. I have a 4" setup that I just RECENTLY added the muffler delete kit to. I barely noticed any difference in sound. In the cab you hear the bypass/blow off or whatever it's called on these trucks. It's been the exact same since I went with the 4" delete.

Anyone who wants to argue that you can max out a 4" for flow on a straight pipe with a stock turbo or any bolt on turbo has drank way to much kool aid... ROFL!

No one said that you could max out 4" exhaust on flow or that you can't make 1000hp with 4" exhaust. Just saying that the 5" helps lower EGT's especially on the higher horse power set ups.

Breaking Habits · May 9, 2013

My theory is that the restriction lies at the outlet of the turbocharger, anything larger than that diameter is purely sound quality alone. 5" does sound substantially better though..

Dzchey21 · May 9, 2013

Powell said:
If you don't plan on upgrading the turbo other than a deeper tone it's down to how you want the exhaust to look. I have a 4" setup that I just RECENTLY added the muffler delete kit to. I barely noticed any difference in sound. In the cab you hear the bypass/blow off or whatever it's called on these trucks. It's been the exact same since I went with the 4" delete.

Anyone who wants to argue that you can max out a 4" for flow on a straight pipe with a stock turbo or any bolt on turbo has drank way to much kool aid... ROFL!

Very true. The downpipe on my race truck is 4 inch... The turbine wheel is the restriction not the exhaust. There is also something to be said about moving warm thin exhaust gases compared to cooler denser air.

Powell · May 9, 2013

Dzchey21 said:
Very true. The downpipe on my race truck is 4 inch... The turbine wheel is the restriction not the exhaust. There is also something to be said about moving warm thin exhaust gases compared to cooler denser air.

Exactly! I have 3" outlets on my GTX35's on my Porsche I have yet to hit a wall on power due to that yet. We've made 1040rwhp on E85 and 1150rwhp on C23 (we literally had intake issues, but much larger one has been added). Now I do have a set of 1.06 A/R housings in case we run into back pressure issues on the .82's. I worry about that WAY before exhaust size.

I go from 3" downpipe to a 4" delete to a 4" straight pipe... Going from 3" downpipe to a 5" delete and 5" straight pipe. Can someone explain with some kind of real data, not seat of the pants feel?