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3'' o2 housing into N1??

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9D9X

10+ Year Contributor
81
0
Jan 20, 2010
Ashburn, Virginia
Hey Guys,
Just wanted to run this by you. I have a 3'' o2 housing with a 46mm wastegate routed back in and N1 turbo back. The N1 as you know starts off at 2.5''. Do you think it is a big deal to have a 3'' o2 going into the 2.5'', do you think it will hurt flow or is it such a small distance that it may be fine...

Thanks
 
Did not see any for 2g awd...Really think it will cause that much turbulance being only 6in or so long.
 
Wow.. never saw that one. Still looks like it necks down at the flange to 2.5'.
 
It will cause some turbulance but shouldnt be anything really to hurt performance. It's not like your going to gain 5hp from opening up a few inches of pipe an extra half inch.
 
It's rare to find a downpipe that doesn't neck down at the entrance because 3" o2 sensor housings are almost nonexistent. That being said, I doubt either of those ebay ones will be 3" at the entrance because that would not work well with nearly every potential buyer.
 
You do not want a bottle neck restriction in the exhaust system.
You can go 2.5" to 3", but do not go 3" to 2.5"
 
Yea I know that. But I was just wandering because it was such a small distance of 3''. Don't you think the 2'' will be a bottle neck too being that close to the turbine.
 
The turbine outlet is not greater then 2" i believe. So running a 2" internal diameter O2 housing is fine.
I too have a PR O2 housing, it's great, flows a shit ton more then any 1G or 2G ported.
Anything smaller after your O2 housing is bad. So you could run a 2.5" exhaust and then have a 3" noise maker at the end if you really want. But I'd think that'd eliminate the purpose of going with 2.5" anyway.
Go with 3" downpipe back end of story.

Nevermind just saw your running a FP green, I'm not sure of the outlet size then.
 
Only thing that sucks is that most of the 2.5" o2 housings are 2" at the bend. Do you think that hurts hp that much..maybe 5 or 10 at the most right.
 
it doesnt hurt HP, it affects flow which relitively can effect HP, use the 3" 02 housing, and get yourself a 3" Punishment-Racing Down-pipe. Its full 3".
 
I don't think it will really make a difference if you only have a few inches of the 2.5" pipe. I did the same thing on my car... I have a 3.5" O2 housing welded to the apex'i downpipe to the 3" exhaust.. I only have about 3" of the 2.5" pipe and it runs fine... I might gain a lil more power if i got rid of the 2.5" and changed it to 3 but i don't think its really worth it.
 
Thanks guys for all the feedback. Please don't think I'm a ding dong, I've been working on dsm's for over 10 yrs now. I just wanted to see what everyones thoughts were. Most of the o2 housings like I said are only 2" max at the bend and the bend is so close to the turbine that maybe a larger o2 would let the turbine spool alittle easier, not having to overcome the wall of the bend being so close and the 3" o2 has such a small distance of 3". I know that on exhaust side you want small to big for flow and on the intake side I know that you want the ports of the intake manifold to be smaller than the head ports and the exhaust manifold ports to be larger than the exhaust ports in the head for flow. Just good to bounce things off each other now and then.

Thanks Again....
 
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