... that modifies the operation of the wastegate by lowering the pressure seen at the wastegate actuator. The wastegate is set for quite a low pressure ("base boost" pressure). The Saab innovation is to use this valve, under electronic control, to control the boost pressure above base boost. The engine management system can then perform tricks like disabling the wastegate temporarily to make the turbo spool up faster and backing off the boost when detonation is detected, so allowing maximum boost to be run commensurate with the grade of fuel and other prevailing conditions. There is, of course, a pressure sensor too so that the management system knows what the boost pressure actually is at any given time.

It's quite clever, really...

The original APC system is well-described at the link below (interestingly, a site for Volvo turbo owners who want to use the Saab system as a performance upgrade). The later system (models with DI) detects detonation in a different way and modulates the valve differently (more smoothly), but the principle is the same.

posted by 62.253....

Volvo APC

• Replacement BPC valves on Aeros....?, Zip, Tue, 11 Jun 2002 07:53:22
  • BPC or BPV?, Bob Davis, Tue, 11 Jun 2002 10:42:06
    • Same as a '90 2.0L turbo, KeithB, Tue, 11 Jun 2002 11:18:49
      • Same part numbers, but..., BillJ, Tue, 11 Jun 2002 11:29:48
        • Re: Same part numbers, but..., Bob Davis, Tue, 11 Jun 2002 15:15:06
        • Re: Same part numbers, but..., KeithB, Tue, 11 Jun 2002 13:11:26
          • It's an electrically-operated bleed valve..., BillJ, Tue, 11 Jun 2002 13:22:14 <-- Viewing This Message
            • Link worked last night. Try again later... n/m, BillJ, Tue, 11 Jun 2002 13:25:50
              • Thanks Bill....., KeithB, Tue, 11 Jun 2002 14:27:23
  • BPC solenoid or BPV?, BillJ, Tue, 11 Jun 2002 09:28:05
    • Power increase with JT system quantified >, Bill Davies, Tue, 11 Jun 2002 11:49:42
      • P.S. Notice you hanging round the performance BB... n/m, BillJ, Tue, 11 Jun 2002 13:11:36
        • Folie de grandeur... (n/m), Bill Davies, Tue, 11 Jun 2002 13:39:43
      • Re: Power increase with JT system quantified >, BillJ, Tue, 11 Jun 2002 12:45:16
        • Re: Power increase with JT system quantified >, ben, Tue, 11 Jun 2002 14:55:26
        • Grande folie..., Bill Davies, Tue, 11 Jun 2002 13:41:56
          • Sanity calms, but madness is more interesting... n/m, BillJ, Tue, 11 Jun 2002 14:10:21
    • I mean the plastic thing screwed to the top of the rad, Zip, Tue, 11 Jun 2002 10:43:02
      • How do you inspect wastegate control rod? n/m, KeithB, Tue, 11 Jun 2002 11:20:42
      • Re: I mean the plastic thing screwed to the top of the, BillJ, Tue, 11 Jun 2002 10:57:19
        • Problem is pretty constant, although..., Zip, Tue, 11 Jun 2002 11:12:56
          • Re: Problem is pretty constant, although..., BillJ, Tue, 11 Jun 2002 11:37:42
    • Wait, are you talking about..., KeithB, Tue, 11 Jun 2002 10:09:58

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