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mark houghton mark houghton is offline
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Join Date: Jul 2008
Location: Central Washington State
Posts: 3,893
1.0 bar is equivalent to 14.5 psi. Thus, .8 bar is 11.6 psi, etc. Stock 930's have the wastegate set to open at .8 bar. Typically, with some simple (but not necessarily inexpensive) modifications, a person can safely run 1.0 bar by changing the spring in the wastegate, installing a larger intercooler to better cool the air charge, and some means of adding additional fuel on full boost (usually an adjustable WUR). And coupled with some means of monitoring your air-to-fuel ratio to assure final tuning is correct.

There are a couple control things going on with boost. One is the wastgate opening up at the pre-determined spring tension (.8 bar) to let some of the exhaust gas bypass the turbo and stop any additional boost from occuring. Another is the boost recirculation valve (not a true blowoff valve since it isn't blowing off to atmosphere) that opens when you take your foot off the gas to shift. It allows all that under-pressure air residing in the intake manifold (actually, in the intercooler and secondary manifold that is part of the recirculation valve assembly) to recirculate back to the intake side of the turbo, vs. trying to force itself back through the turbo which will put strain on the turbo and cause it to stall...thus increasing your turbo lag. Also, when on boost, your WUR will react accordingly and cause an increase in fuel to the injectors to assure a rich enough mixture to both cool the cylinders and prevent detonation.

More boost pressure = more power, but not without some level of risk if not sorted out correctly. Until you gain more knowledge on these wonderful machines I would recommend staying stock and just enjoying it as-is.
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 11-07-2010, 09:10 AM
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