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Not quite accurate ... Posted by RS [Email] (#15) [Profile/Gallery] (more from RS) on Tue, 13 Jun 2017 06:38:48 In Reply to: Re: APC pin 12 (Solenoid), low voltage woes., Bloodnose [Profile/Gallery] , Mon, 12 Jun 2017 13:40:34 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Apologies for chiming in like this ...
You might be thinking of the EZK controller that 16-valve non-turbos have. The EZK does monitor the knock sensor and retards spark timing to control knock.
The ECU only controls fuel delivery. It does this based on RPM, AMM flow signal, and (when the engine has warmed up) O2 sensor reading. It doesn't have any input from the knock sensor.
The APC looks at intake manifold pressure, knock sensor, and RPM. Its control algorithms use those parameters to modulate the solenoid (which controls wastegate position) to limit boost and, this, control knock. When it senses knock, it limits boost.
When my '89 SPG had some significant boost issues, it turned out that the APC had gone bad (staying out late, smoking, hanging around with unsavory APCs :-). When I replaced it with a used unit from an early 9k, things got better. I suspect that the old one had a cold solder joint.
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