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Re: Help understanding base boost vs normal boost Posted by RS [Email] ![]() ![]() ![]() In Reply to: Help understanding base boost vs normal boost, Bob B, Tue, 19 Aug 2003 20:15:27 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Base boost is what you physically set the wastegate for with the APC disabled. It's set like that so, when the APC is active, it can back the boost down to a level at which the engine is protected from detonation when the APC senses knock. Base boost is purposely set low. Increasing base boost won't increase ultimate boost (unless you set it beyond what the APC would allow - that's *really* asking for trouble.) Increasing base boost can lead you to a situation where you can burn a pistion if it's not done judiciously.
The wastegate is a flap on the turbo that can divert exhaust gasses to the turbine impeller or away from the impeller depending on its position. More exhaust gasses going to the turbine impeller means that the compressor wheel spins faster and pushes more air into the intake. It's actuated by a spring-backed diaphragm which is controlled through pressure diverted by the APC solenoid above the radiator.
The APC controls ultimate boost (that's what you refer to as normal boost). It's set in the APC for a maximum pressure that it will allow, as measured by a pressure sensor under the dash. It will back boost down to base boost under a few conditions to protect the engine - knock, brake lights on, interrupted knock sensor circuit, loss of power to the APC.
Increasing boost is a double-edged sword. Lots of boost makes for a fun ride. However, the transmission is the weak point in the C900. What you gain in fun can kinda be dampened by the need for an early transmission rebuild. SAAB was purposely conservative in their design for the APC.
posted by 63.148.1...
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