N/A Downpipe Size Question

[turbonicsperformance]

Originally Posted by 907mge

I have a 1990 N/A with a 3in Hks catback(yes I know it is overkill) with a 3in high flow cat. I now have the pacesetter header that after some minor modifications I’m going to install. My question is if I should make the current 2in downpipe for it larger?

it depends on what you are trying to do if you want all out power you should go one full size all the way back actually ending up a tiny bit smaller at exit as the whole point of the exhaust is to keep your air speed up as your exhaust gets further it slows just like an irrigation system so they downsize the hose as you would your exhaust unfortunately this would be extremely hard to do so we just run one full size in our cars

with adding a 3 inch "downpipe" you will get a deeper tone and you will get a steadier fllow than with a 2 inch as with the 3 inch you will only have 1 slow point in your exhaust then the rest of the way it should flow steadily

with keeping the 2inch you will have a slow point at your 2-1 point of your header and then at your 2-3 point of your exhaust you will have plenty of back pressure maybe a bit too much to make full power and you will have a different tone as your exhaust will flow fast at the header and slow in your exhaust

basically the 3 inch dp would be your better way to go depending on the coating on your headers and the way you build it and as for the 3 inch on the n/a its not that overkill its just about perfect