2.5 inch exhaust vrs 3 inch exhaust can you tell a diference?

[AN89HATCH]

I m about to get my exhaust made, but I can not decide weather to go 3 inch, or 2.5 inch. Will I really be abble to notice a difference between a 2.5 inch, and a 3 inch exhaust on a turbo ka?

[Projex240]

Turbos rely on exhaust flow. IN this case, the bigger really is the better. The turbo needs to flow as mucha s possible. People will argue that until a certain boost point is reached, then you dont *need* 3 inch. If you put a 2.5" on then a 3" on , youll notice the difference in your top-end gain.

-Josh

[nissanfanatic]

Yes you can tell the difference. I just upgraded my downpipe from a 2.5" to a 3" and spool times are much better. Like 500rpm better. And the powerband is much smoother. I even get a little pull in 5th gear now.

[hysteria]

depends on power app, but in general restrictive exhaust = no good.

you want to minimize friction and allow the gases to flow as freely as possible.

conversely though the 3 inch will weigh more, so decide on your power application and then make your decision.

3 inch will leave room for upgrades though...

use the search button if it's working, because there are good threads out there covering this topic 100000 times.

[skatanic28]

im planning to run a 2.5 inch catback and then have an e-cutout right after the 3" boostdesigns downpipe dumping to the side. i hate loudness all the time so a slight drop in power is fine with me. im sure you would see noticable gains going with 3 over 2.5 though.

[C-Kwik]

Turbos rely on pressure differential. The lower the pressure you have behind the turbo, the less you need before it to make the same boost. This lowers backpressure to the motor and in turn, frees up more power. Unlike N/A motors which need good exhaust gas velocity, turbos benefit more from the lower pressure than it does with the high gas velocity. For the most part, you will see a gain in power and boost response with a larger exhaust behind the turbo. I felt a decent difference going from 60mm to 80mm when I had my KAT.