Thread: Exhaust size

stock is 2" to 2 1/4 i think. I would suggest 3" all the way back.

95% of the downpipes that are mass produced like the megan racing and apexi will bolt up to a stock style o2 housing. The megan racing is a 2.75"ID flange that bolts onto a stock housing with not problem. and then expands out to 3" just before the flex section. The apexi is 2.5"ID flange that is 2.5" until just after the flex section and then it expands out to 3" and on the awd model it expands to 3.3" somewhere in the mid pipe before the rear diff. With the setup you have listed just get a 2.5" megan o2 housing or a ported out stock housing and you will be ready to rock.

The only O2 housing I've found that has a 3" outlet is VRS. They sell downpipes with true 3" inlets also.

Originally Posted by MercenaryX2

The only O2 housing I've found that has a 3" outlet is VRS. They sell downpipes with true 3" inlets also.

They are not as easy to find as alot of the others. If you have links can you please post them?

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STM: VRS TURBO-BACK EXHAUST | 90-99 DSM

Originally Posted by maddog

Hi Guys, I am currently buying my parts to do my build this spring. My question today is about exhaust size, I have a 20g turbo w/1000cc injectors, fmic, ecm link, 1g bov, I also have a downpipe that is 2.5" so I am looking at either using my stock O2 housing or buying a Megan racing 2.5" O2 housing. With this setup will the 2.5" exhaust be ok or should I just do 3" all the way? Also what is the size of the stock exhaust?

thanks

There really probably wont be any benefits seen from going from a 2.5" to 3" o2 housing, but there will be going from the stock to the 2.5"

I think I read somewhere that the piping doesn't have to be as big closer to the exhaust ports, but as the exhaust gases cool down they take up more space or something, and that's why its beneficial to go with a bigger pipe size. For your setup any 2.5" o2 housing will be fine. I would switch to a 3" exhaust for the rest of the way back though.