21/4 or 21/2 exhaust??

[Joey's mx]

Hey putting new exhaust on my car header back with hi-flow cat, what size would be best?? I have a probe header, shaved, ported, polished head, bored throttle body, adj. fuel pressure reg., underdrive pulley, lightned flywheel, ported intake manifold, adj. cam gears, larger fuel rail, 330cc injectors, cold air intake....And thats all on the 1.6 DOHC!! Thanks

[Joe Carlson]

Go with 2.25in exuast, i have 2.5 on my bp, and it's awesome on the upper end, but it really lacks on the low end and doesn't pick up til 3,500 rpm's. Once i get mine all back together, and some more cash i'm going with 2.25, and I'm also running straight through exuast just a magnaflow bomber, and a resinator, so maybe a cat will give you the back pressure you need, but i wouldn't think so.

[Custommx3]

rule of thumb is 1 inch per liter, 1.8" for a 1.8L, ect, uless u go turbo. Getting too big of exhaust will actually do more harm than good.

[jaydog5678]

Originally posted by Custommx3:
rule of thumb is 1 inch per liter, 1.8" for a 1.8L, ect, uless u go turbo. Getting too big of exhaust will actually do more harm than good.

So if I had an 8 liter V-10, I'd need an 8" exhaust. j/k

[Custommx3]

yep, dual 4" pipes

[LongJohn]

Originally posted by Custommx3:
rule of thumb is 1 inch per liter, 1.8" for a 1.8L, ect, uless u go turbo. Getting too big of exhaust will actually do more harm than good.

Seems like a tricky rule to use. The flow of the pipe is equal to the cross-sectional area. A 4" pipe would flow 4 times as much as a 2" pipe. A 4L engine would exhaust only twice a 2L engine (keeping RPMs and everything else equal).

[Typhoonk]

so, I have a 1.8L DOHC LX motor, with a stock US spec header, to a custom 2inch downpipe, stock catalytic, then 2 1/4inch to a inline resanator, then 2 1/4inch pipe to a stock protege muffler...
I think I got that all.....seems pretty mix and match. But I heard something about going from a large pipe to a small pipe or something for perforance? I wasn't going for performance just a quieter exhaust....
Any idea what my power is? I feel like the top end is good the bottom ok, and the middle kinda sucks?

[Casino]

save your money u may gain on top end but lower rpms will suffer and how often do u really bust it lose ?

[Josh]

Originally posted by Taillon:
Hey putting new exhaust on my car header back with hi-flow cat, what size would be best?? I have a probe header, shaved, ported, polished head, bored throttle body, adj. fuel pressure reg., underdrive pulley, lightned flywheel, ported intake manifold, adj. cam gears, larger fuel rail, 330cc injectors, cold air intake....And thats all on the 1.6 DOHC!! Thanks

330 cc injectors thies are the size of injectors im running with 16psi of boost, why so big? i hope you have some wild cams in there if not you could risk gas washing your rings out. BP injectors will provide more than enough fuel if you need more. also you should look into a fuel management, like a Greddy E-manage, or apexi AFC. the Greddy is better but also more. then you can get it all dyno tuned to make the most of what you have.

if your not going turbo then 2" would be the best for the 1.6L. 2.25" would be ok, but from personal experience 2.25 is too big. when i was N/A i had port and pollish and wild cams, but it was only good in the high end, and it was way way too loud as well. but i only had it n/a for a short time it was in prep for the turbo.