Alright I know Turbo's create their own back pressure so I don't want to get into the dynamics of back pressure.

I was planning on purchasing the SZ 3" Downpipes (4 bolt) but I started thinking that since each turbo is being fed exhaust from essentially a 1.5 liter engine is it necessary/a proven power difference to use 3" vs the 2.5".

I have HKS Hi-Power Exhaust so it will reduce down to 2.5 either way.

Tim

 

its been proven a full 3" exhaust will perform better on the turbo Z32 than a 2.5 as for mixing 3" DP with a 2.5" cat-back im not to sure... it might be slightly beneficial but probably not AS good as a full 3" hey if its the same price i say go 3"

 

Actually for a 4bolt 3" its $675, a 2.5 Stainless steel is $475 and aluminized is $415 haha I doubt I'll change my Cat-Back HKS is nice!!!

 

If money is an issue, you won't regret 2.5" downpipes (I have 2.5"). But if you can swing it, you will get better spool from a 3" setup (even if your catback is 2.5" - that's because the exhaust gas will have cooled a bit by the time it reaches the catback). The goal is to allow the gas to escape the turbo as freely as possible.

Also, 3" absolutely won't hurt performance, and it allows room to upgrade to full 3" later on if you choose to do so (whether 3" SZ exhaust or custom 3" piping on the HKS like I plan on doing).

 

Money isn't a problem I wont be purchasing parts for a few months. Only problems is then I have to buy the 3" reduced to 2.5" testpipes aswell (now that I think about it an exhaust shop could fab something up...)

Kinda on the fence my Z already spools up super quick with my FMIC installed (Zlover's favorite Z32 performance mod ) I'm sure once I add some more power it'll spool up even quicker. I doubt I would regret 2.5....mabye I'll save 3" for my breaking point on my Z and I cave and upgrade to larger 5 bolt turbo's...hmm

Any other opinions/experience would be appreciated.

Tim

 

I just ordered the 2.5" due ot money, but make sure you get stainless steel not aluminized.

 

In all honesty, an aluminized downpipe isn't going to rust any time soon... its position and how hot it gets prevents water/condensation from sitting in it (which is the main source of rust in exhaust systems).

And btw, Greg Dupree says approximate 10hp difference between full 3" system and 3" DP/TP with 2.5" catback.

 

that and salt on the roads. hopefully z's aren't being driven in any kind of salty road conditions though.

 

How do you plan to do 3" on the HKS? Take out the Resonator section and go 3" until it meets the Muffler sections or have a shop fab up 3" all the way to the mufflers?