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Re: adjustable boost for your turbo audi
I found an easy way to make your boost adjustable on a turbo audi. Go
buy an adjustable air pressure regulator (i got mine at sears) get it as
close to 0-25 lbs as you can but you can use a big one too ( mine goes
to 125 psi. Take the hose off the back of the wastegate run a line into
???125??? Did you perhaps drop a decimal point, and mean 12.5 PSI?
What you are doing (a "well known" hack, by the way) is basically to
back-bias the atmospheric reference pressure. Every PSI you feed in
directly translates to a PSI rise in the wastegate operating curve,
and an extra PSI into the engine manifold.
Unless you are very good and know what you are doing, a 0-5 PSI regu-
lator is adequate (I frankly doubt there is a ECU out there that will
allow 5PSI over what the stock wastegate/ECU are set for); 10PSI
overboost is definitely approaching grenade territory; 25PSI will
destroy your engine faster than you can utter your favorite expletive;
you will never make 125PSI as the shrapnel from your exploding engine
will have ripped the engine compartment apart long before the boost
could build to that level.
Further, if you at all "pushing the envelope", make sure you use a
thermally-compensated regulator (I betcha your SearsSpecial ain't!),
as regular regulators (so to speak) can easily vary several PSI from
cool morning to hot afternoon sun-soak.
P.S. Some of the wastegates have an adjustable spring perch (hex
"allen" bolt in top/center of waste, underneath the label/sticker)
good for a coupla PSI . . .