adzer

iTrader: (13)

whats the advantage with a 3" system over smaller sized pipes??

would car need mapped?

scooby-93

it would needed mapped if you removed the down pipe. but not if you only are going to get a cat back. with a 3" turbo back i have been told that you can loose too much back pressure therefore low down torque is lost compared to a 2.5" system. if you are after 340/350bhp+ get a 3" if not 2.5"

adzer

iTrader: (13)

its just that i removed a system off my car and put it in my shed and put on my smaller system coz i liked the look of the angled rear silencer.

so not sure if i should put the 3" system back on or sell it and make some money for my rebuild?

help2003

iTrader: (1)

What year is the car?

i removed my 2.5 and went for a full 3" decat system which didnt need a remap, and it pulls alot better and the noise is great

adzer

iTrader: (13)

93 WRX RA MATE

silent running

No turbocharged car needs or wants ANY back pressure at all downstream of the turbo. The rules of NA cars where you might need to tune runner lengths in your manifold, experiment with 4-2-1, 4-1 designs etc are mostly thrown away. As long as you can get fast, even gas flow up to your turbo, from there onwards the best solution would be to have no further exhaust at all AFAIK.

The drawbacks of a 3" system over 2.5" are basically noise and possibly weight depending on how it's constructed.