Hey guys.....first time posting here. Just wanted to say this site is invaluable with all the information and expert advice I found here.

I know the 4" vs 5" topic has been beat to death. I was reading through a bunch of the threads and didn't find an answer to the question I have. Based on some past experience in plumbing, this is my understanding. A system can only flow as much as the smallest restriction in said system. So, if that is true, and my end plan is having a 4" downpipe on my new turbo.....nothing larger than 4" exhaust should benefit any performance gains. Is that a true statement....or am I off my rocker?

Please keep in mind that I have a performance goal in mind for this truck, not a cosmetic one. So, the sound/look side of this discussion isn't really relevant to me.

Thanks again for all the great info guys!

 

You won't get a 4" downpipe to fit with out major firewall work.

All you need is a 3" downpipe and 4" exhaust.
Thus setup will support 500hp

 

Unless you run it straight up thru the hood

 

Thanks for the replies guys. Let's just talk hypotheticals here then.....let's say I perform the needed mods to install a 4" downpipe. Would there be any need to have anything larger after that?

 

4" DP TO 4" exhaust. The no you don't need any bigger.

3" DP to 3" exhaust won't flow what a 3" to 4" will.

Remember exhaust bouncing of the walls of the pipe and bends in the pipe cause restriction.

There is really no need to go bigger then 4" exhaust unless you want a deeper sound.

 

I have a 3.5" (I think it was advertised as 3.5") downpipe, stock cat con, and 4" exhaust / muffler exiting at the stock location. I'm quite happy with this setup.

It's a Diamond Eye system. I'm NOT happy with the installer nor the company, but that's an entirely different story. If I had it to do over, I'd go with MBRP.