Date: 04/10/01 02:22:48 AM Pacific Daylight Time
From: Ben@mrtrally.com.au (Ben Taylor)
To: Ssspoon@aol.com
Hi Larry.
Thanks for your reply. Sorry for the delayed response, but it took me several
days to read your massive email!!
Just kidding... OK - now we are on the right wave length! I am aware of what you were
discussing, but my original thoughts were that the 2.2 Turbo you have fitted
to your Legacy's were similar in design to our 2.2 naturally aspirated
versions (ie same engine but with a turbo running low boost hanging off the
side).
If you have the higher spec cooling systems, pistons, oil squirters in
cylinders, etc, etc, then you will also have the heads to match. Changing to
the heads from other models will NOT be a step up. If anything it will be an
expensive exercise for little or no gain.
We did some research over here looking at fitting the 2.5 heads to the WRX
EJ20 engine, to give it some better breathing ability and it was a hell of a
lot of stuffing around for next to no gain. Better results on that engine are
had by porting/polishing the standard heads, and ironically, fitting revised
pistons and a stroker crank which take engine capacity out to just under
2200cc (like your Legacy's).
The list of mods I would make to the 2200cc turbo Legacy's or more
torque/power, in this order, are:
1/ Intercooler
2/ Bigger intercooler!
3/ 3 inch exhaust system
4/ Free flowing intake
5/ Boost increase (around 15-16PSi should be sustainable in most conditions
with 96 RON or greater fuel if engine is based on same block/pistons etc
as our 1994cc turbo EJ20)
6/ Revised programmable engine management with custom tuning to suit mods
7/ Larger ball bearing turbo (STi VF23 or VF22)
8/ Pre turbo extractors/headers
8/ Forged pistons, rods, port and polish heads, etc
9/ Revised fuel system (new fuel rails to prevent leaning out in 2nd cylinder
under high boost)
10/ More boost (around 20Psi should be easily sustainable with the stronger
engine internals
By now you should have in excess of 370-380hp and have a smile from ear to
ear. However, things that weren't mentioned that should be looked at are
suspension, brakes, clutch and gearbox.
I hope this helps further Larry.
Kind Regards
Ben
MRT Performance "We Rally, You Win !"
Subj: Re: right wavelength swapping heads thanx again
Date: 04/11/01 100:26 PM Pacific Daylight Time
From: Ssspoon
To: Ben@mrtrally.com.au
Hey Ben mate, now we're cooking with gas. By Jove I think you've got it!
And your recommendations look right on. I really appreciate your feedback
about the actual experience you found when swapping turbo 2.0 heads for N/A
2.5 heads. Your suggestions that there is not much to gain has come from
other sources also. I think a large part of our interest in this direction
has been the result of a Cobb Tuning technical article discussing cylinder
head modifications, which shows graphical evidence to support your findings;
the DOHC 2.0 turbo heads and both the SOHC and DOHC 2.5 N/A heads show very
close flow numbers. However this same study shows the US spec Turbo Legacy
SOHC 2.2 turbo head numbers to fall quite short of the others. Our SOHC 2.2
turbo must be a unique design, unlike either of the N/A 2.5's or the 2.0
turbo. I thought it was the same as the 2.0 turbo.
The article and flowcharts are here
> http://www.cobbtuning.com/impreza/engin ... heads.html <
What we're (US Turbo Legacy owners) missing then is support for our HOPES and
WISHES that the SOHC 2.2 turbo head can be made to perform on par or better
than the 2.5 N/A heads can be, as has been suggested by a couple of sources.
But I have to say from those charts, it looks like it would have to be one
hell of a head job. Otherwise, we're back to talking about some kind of swap
for the radicals out there who want the ultimate flow. And along those
lines, I have to wonder about how the difference in water jacket location is
addressed by those who have done the swap? Anybody out there on the list
have any answers, or even any theories at this point? Again Ben, all of our
discussions have been for the benefit of those members on the BC-BF Legacy
list, which I have been relaying everything to. Please feel free to join in
or just check out the action by joining at
> http://groups.yahoo.com/group/BC-BFLegacyWorks <
Thanks again, Larry Bewildered Witherspoon
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