legacycentral bbs

Turbo engines must have fairly mild cams, as the amount of overlap that works for a hot NA engine will allow unburned air/fuel mixture to blow in the intake valve and right out the simultaneously open exhaust valve.

My son Joel has a 98 Impreza 2.5 twin cam with a big Garett turbo and big JC Sports top-mount intercooler, running 5psi.

His car has better low end torque than my EJ22T turbo and is all-around quicker. His higher compression (9.5 versus my 8.0) provides an inherent advantage at no or low boost. His stock cam profile appears to be just fine. Incidentally, his car eats engine bottom ends.

The newest WRX engine has quad cams (2 each bank), so I don't think the late model SOHC 4-valve technology is the ultimate for forced induction applications.

Last, but not least, There are people actively working on 2.5 heads on EJ22T engines. I mentioned this to rally mechanic Richard Buckner and he said that it was do-able, but that some special machining is required.

I genuinely believe that when those on the bleeding edge get the bugs sorted out, the EJ22T with EJ25 twin cam heads may be the ultimate engine for the US market.

Bill Robinson
92 turbo sedan with a few mods, but stock engine internals.



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zZz <http://docs.yahoo.com/info/terms/> .

Yes, for the EJ20 engines we use the standard 2.5l (DOHC) Subaru outback
engine heads 1997-1998 only, previous models had smaller buckets. (heaps
cheaper because nobody really knows how good these heads are) I can pick a
set of these up for $1,100.00 and the impreza equal equivalent $2,500.00.
The outback heads have over head shims so need to convert to on valve. The
inlet ports are smaller so you need to bore these out to match the EJ20
ports.

Cams - Yes the N/A cams are more wild than the turbo ones. We go for 355mm
lift and 230deg duration at 50deg, the cams are built up and cost $400.00 a
set of 4. By building the cams up you don't have to shag around with shims
etc, because the lift is not changing.

Dan


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