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Old 08-10-2010, 04:01 PM   #1
DNut
Scooby Specialist
 
Member#: 151739
Join Date: Jun 2007
Chapter/Region: NESIC
Location: Lakeville, MA
Default ’99 2.5L SOHC intake manifold of any use on a turbo motor?

I’ve been reading on here that the ‘05+ 2.5L SOHC intake is a good, relatively inexpensive upgrade for the WRX and STi intake manifolds because of the runner design and larger plenum. Besides some potential work around the fuel rails and injectors (Maybe not…still not clear on this), the only major issues are having to go with a FMIC (Due to lack of room for a TMIC due to the larger plenum) and adapting a Drive-by-cable (DBC) throttle body to this manifold, which is Drive-By-Wire (DBW). The DBW throttle body mounting would only be an issue with the earlier WRXs (02-05?) I think.


Now, from what I understand, the ’99 2.5L manifold is able to accept WRX injectors without any modifications, correct?

Also, being a phase II design, it has the same bolt pattern as the DOHC heads, right? (Albeit with smaller ports from what I’ve read)

And, even though the inner diameter of the runners may be smaller than the WRX/STi manifold (I don’t have any actual numbers, just posts that seem to mention this), wouldn’t there be some benefit to using an intake manifold with longer runners to promote low-speed torque?

Yes, you’d lose some top-end, but shifting the powerband lower on a small-displacement motor like the EJ205 (That really doesn’t rev too high in the first place) may not be a bad thing.

I’m thinking that the ’99 RS manifold might be a good second choice to the ‘05+ manifold, especially since it’s already designed for a DBC throttle body.

Thoughts on this from people who actually know more about Subaru motors than me?
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