Im getting a full stainless steel exhaust done for my new calais, i was thinking of maybe goin to 3.5in. Has anybody ran a 3.5in exhaust and found significant horsepower gains?

3 Inch is plenty,Unless your running a huge mother of a Turbo go bigger Exhaust.

go 3.5 for sure. one day you will regret not using 3.5" pipe if you dont do it. that is if big hp is your aim

so there would be noticable gains by changing from 3" to 3.5"?

Matters how much power your pushing, you dont want to go too big, cause if its too big, you can lose a bit of power. 3inch should be fine if your not pulling massive power. But if your after a monster, go 3 and a half Some original photos have not been recovered yet.

Quote: Originally Posted by Blink Matters how much power your pushing, you dont want to go too big, cause if its too big, you can lose a bit of power. fill me in on this?

Im probably wrong, but thats what I was lead to believe.

On an NA you can lose torque or shift torque if you make the primary pipes to big as it effects scavenging, but if you have an of the shelf header set, changing the exhaust from the cat back will have minimal effect. Its the headers or tuned part of the exhaust you don't want to mess with, unless you know what you want/doing. On a turbo, after the turbine outlet, the bigger the exhaust the better, simple.

how big does the turbo have to be to benifit from a 3.5 inch? Say you were running a GT30 (external gate) and wanted to make around 250rwkw on 14psi? Would the ideal exhaust set up be a high flowing custom exhaust manifold into a 4 inch dump and a 3 inch exhaust or would a 3.5 be better? I'm just not sure if the straight GT30 is big enough to benifit?

Quote: Originally Posted by Blink Im probably wrong then why post??

I must have been thinking of NA, as stated above. Apologies for trying to help, we cant always be right.

Bigger the better and no cat converter and minimal mufflers (read 1) is better again....lol! I read turbine oultet size multiplied by 1.25 for dump size. Matt....you noob.lmao.

I dunno about this argument, I know a guy with a turbo ford pushing 23 or so psi. Runs a 3 inch all the way. It makes 407rwkw with the full exhaust on and 428 rwkw with no exhaust. Not a huge increase. I would say the mufflers would be the biggest factor rather than stepping up over 3 inch in exhaust size.

what kind of indoor dyno centre let him on the rollers with no exhaust haha?! That would of been ridiculously painful on the ears

people run 10z/ high 9z with a 3" all the way. i guess if u plan on going faster go 4 it

sometimes its not just about how fast people run with what, i just wanna make the maximum power on the minimum boost possible with mimimal lag so yeah a 3.5 inch exhaust may help me out in a big way i just wannna know. Also im pretty sure alot of 9 and 10 sec vl's take their exhausts off when they run.

With a bigger pipe you will get more lag. I went from a 2 inch to a 3 inch exhaust on my EB when I had it and the time the turbo took to get onto boost was heaps longer.

did you use the stock dump and front pipe? As the bigger they are, the quicker the exhaust gets out of the exhaust housing... so the quicker it has to spool?

Nah mate, it was on a falcon, Both times were using a 3 inch dump. So before it was a 3 inch dump into a 2 inch exhaust, less top end more low end power. After it was a 3 inch all the way. Much more top end, heaps more lag.

thats true. my mates got a dato 280zx converted to turbo 3" exhaust was too big ran better and went harder with a 2.5" weird.