Some of these definitions are in the Saabnet FAQ's, which can be found off the home page.

When the car is on boost, and then no longer needs to be (throttle is lifted), the built up pressure needs to be vented, or it may violently stop the turbo, eventually leading to damage.

To prevent this, the car vents the pressure when the manifold reads vacuum, either by recirculating it back to the air-box (bypass valve (=diverter valve)) or blowing it off to the atmosphere (blow-off valve). Both of these are sometimes also called "Hooter" or "Dump" valves, depending on who prefers what jargon. Both of these valve types have a vacuum line leading to them to open them at the appropriate time, and attach to the pipe the feeds the intake from the turbo.

A BPC, or "Boost-Pressure Control Solenoid", is the small black plastic box above your radiator on the right side of the car. It has three hoses leading to it, from the Turbo, Intake, and Wastegate, and an electrical connection. This is controlled by the ECU based on various engine parameter readings, and is used to control your boost levels. If pressure from the turbo rises above what the ECU deems fit, it will vent pressure to the wastegate, which opens to vent gases away from the turbo. Basically, the BPC tries to keep boost somewhere between your "base boost" (around 6psi, equivalent to hooking the turbo pressure line directly to the wastegate) and max boost (fuel cut-off point) based on various factors and while preventing knocking.

Best,

Lutfisk


posted by 132.236.139...

• I finally bit the bullet, Tim, Thu, 3 Apr 2003 21:50:26
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    • Please explain to me..., Tim, Fri, 4 Apr 2003 12:17:48
      • Quick answers, Lutfisk, Fri, 4 Apr 2003 15:02:40 <-- Viewing This Message
    • Re: Can you use a BOV?, JC, Fri, 4 Apr 2003 07:25:51
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