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Hey folks,
Over the past couple of years, I have been occasionally back and forth with "Turbo
Tom" on the Subaru list who has been in the turbo business forever. I sent him a
brief rundown of the recent thread and Rusty's [mis]adventures and asked for his
thoughts. Here is his reply. Makes pretty good sense to me...
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Turbo-normalizing is for the guys who already have enough power at sea-level.
Charge-air temps are EVERYTHING. The flying rotary turbo guy should measure his.
As you might imagine, 30-inches of MAP at 80F degrees is not at all the same thing
as 30-inches of MAP at 140-150F degrees. That's a pretty typical output temp for a
well-matched turbo. So yes, intercooling is a MUST.
Also, centrifugal compressors are way below 50% eff at less than 10" of boost.
That's where most compressor maps start. Operating "off the map" is never a good
thing. It adds tremendous heat for no boost, a poor trade-off. And yes, you are
correct. It would take a few pounds of boost just to make
up for the density loss from heating. About 10 psi with no intercooler, 3 psi with.
Av gas give great margins of safety with boost. We ran 50" MAP on car gas. Hey,
testing to destruction [commonly shortened to just "testing"] is a BITCH, and not
for everyone. It only looks easy. ;-)
Will call later in the week.
TT
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Rusty,
Where are you measuring charge temp? Is it not an input to Tracy's fuel control?
Can you capture and monitor it? Additionally, if you have excess heat rejection
resources (oversize oil coolers, radiators, etc.) perhaps you could lighten up on
that stuff and get some sort (any sort at all) of intercooler in there. I haven't
seen your installation, and am not even an RV guy, but it just seems as if there
MUST be SOME way to get what you need in there without the cowl getting this thyroid
condition you describe. Also, TT seems to confirm what a number of folks are
suggesting that you can give it 6 or 8 psi of boost and see what happens - the
chance of screwing anything up at that level seems pretty remote.
If we can isolate and quantify the problem .... Jim S.
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