What size exhaust?

[Telly896]

I'm fixing up a Vp Berlina that i bought for 400 dollars, i wanted to know what size exhaust i should get? considering im on my p's and dont want to be pulled over to much? any suggestions? Cheers

[feet eatin chickens]

go down to your local exhaust shop and get a quote for a 1 1/2 inch from the cat back, good power gains and consistant flow, but doesnt sound overly loud. problem with large exhaust systems is that there is back pressure lost in the exhaust thus causes less power..

[levymetal]

1 1/2 inch, you're joking right?

2 1/2 inch will be fine, that's what most people get. they are cheap on ebay and easy to fit yourself. not_an_abba_fan also sells them on here. if you're worried about noise then get the one which has a muffler and a resonator (not a straight rear pipe).

[Reaper]

^^^ as above.

2 1/2" redback cat back system will do you well

Reaper

[Zuicider]

go all out be outragous go the hole hog 4 inch ricer spec. i had 2.5 inch redback was fine but need more wank so i got a 3 inch

[NOT.BT1]

ive got a 2 1/2in stainless cat back on my vn with twin 3in dump tips its not overly loud unless im giving it a gutfull and im on my P's and havent had any problems with the cops

[TheRealShifter]

go down to your local exhaust shop and get a quote for a 1 1/2 inch from the cat back, good power gains and consistant flow, but doesnt sound overly loud. problem with large exhaust systems is that there is back pressure lost in the exhaust thus causes less power..

I thought that larger exhaust systems would actually increase power as the pressure is decreased in the pipes which helps to drag out the exhaust gasses. Am I wrong or is it beneficial like this only up to a certain size?

[levymetal]

I thought that larger exhaust systems would actually increase power as the pressure is decreased in the pipes which helps to drag out the exhaust gasses. Am I wrong or is it beneficial like this only up to a certain size?

it's easier to understand if you think of it in extremes. if you had a 1" exhaust, your engine would be fighting hard to push the exhaust gasses out of the cylinders due to the backpressure, which means you'd lose power. now, say you had a 10" exhaust, the backpressure problem is gone - but of course your engine is still using up some power to push the exhaust out of the cylinder. how can you improve on this? well, how about if you could suck the exhaust out of the engine? that's what the correct size exhaust does. the moving gas actually helps to suck the exhaust out of the cylinder (like a vacuum), so the engine doesn't have to work as hard to get rid of it. 2.5" seems to be the sweet spot for our cars. any less and you have backpressure. any more and you might lose flow. if you want crazy flow then get a twin exhaust with an x-pipe. the way x-pipes work is really interesting

i guess that's where the backpressure myth came from though. people started chucking massive exhausts on their cars and ended up losing power, so they incorrectly assumed that they needed backpressure. what they actually needed what the correct size exhaust that maximised flow. afaik backpressure is only required in 2 stroke engines and not 4.