zapp168

iTrader: (7)

I did a search but got some conflicts. The smaller 2 1/2 spools faster, but will it restrict too much at high rpms? I am using a Garrett STS turbo on a mildly cammed LS1.

5.3-on-steroids

iTrader: (3)

I wouldn't do 2.5", no matter how you look at it thats an awful small pipe to be feeding a T4 and to push all the gasses from a 5.7 through. I did 2 2.5" pipes into a single 3" on my rear mount and it spools like crazy and has great top end, the secret to keeping spool times low and building boost is retaining all the heat you can and double even triple header wrapping the pipes, and of course having no leaks. good luck

ZL1Killa

iTrader: (17)

all of mine is 3 inch. absolutely love it. grab you a 70mm or 72mm and you will be fine. wrap all exhaust and put a turbo blanket on it.

zapp168

iTrader: (7)

My last STS in my 98 was all 3" but I had already installed LT headers, I was not impressed with the spool time, but I liked the over all feel. I am putting this in a 93 Toyota pickup and I am still figuring out how to fit it all in. I ordered the CTS-V exh manifolds cause they look real tight, if they don't go I am going to get headers and make them fit and wrap them the best I can. Thanks....

ZL1Killa

iTrader: (17)

headers = suck for rear mount. headers are for NA cars and Supercharged cars or front mounts.

manifolds or log style manifolds are for rear mounts.

nodrok

Do a search i believe fireball (or one of the other big turbo guys) had a thread with turbo testing and all different size exhaust. Youll be surprised at what they determined. Smaller than you would think.

RooRnZ28

iTrader: (14)

I ran 2.5" when I had my rear mount. It spooled faster but was a restriction on the top end (stock 5.7). Power would start to dip after 5500rpms.

Orr89rocz

iTrader: (13)

Doesnt power usually start to dip after 5500 anyway on these cars stock?

3800SII

Yes, but it is different ball game when you add FI. Car will keep pulling all the way to the redline with a good setup.

zapp168

iTrader: (7)

Well I am putting this setup in a 93 Toyota pickup so I won't be all out racing it too much, I think over 5500 RPMs will be hairy anyway...LOL. I will check search again for that thread, I remember seeing it, but could not find it. I have tried everything for manifolds including the CTS-V ones that fit tight. I ended up last night making a drives side header from cutting up old headers as nobody makes headers for this swap. Thank you for the replies......