Turbo control in a GM ECM

[Ludis Langens]

Shannen Durphey <shannen at mcn.net> wrote:
>What did this ECM come out of?

The version with the extra (wastegate?) PWM output is from a 1985 Pontiac
Fiero with the 2.8 MPFI V6.

>The turbocharged diesels with efi (94-current 6.5) use a pwm control to
>a solenoid in the vacuum line to the wastegate.

Vacuum?  Vacuum?  During turbo boost?  :-)

>Boost is measured by a map sensor.

Yup.  And it also "runs" the engine.

>No ground for the solenoid results in vacuum vented to atmosphere and no
>boost.  Any trouble and the ECM pulls the plug on boost.

This seems to match the logic in the function.

>I don't know why the solenoid would
>ever be fully grounded, the pickup never goes over 90% on time.

It looks like the function will ground the output 99.9% when there is no
boost.  I haven't figured out the logic enough to say what range of computed
values it will produce.

                   unsigned long BinToBCD(unsigned long i) {unsigned long t;
Ludis Langens         return i ? (t = BinToBCD(i >> 1), (t << 1) + (i & 1) + 
ludis at netcom.com                 (t + 858993459 >> 2 & 572662306) * 3) : 0;}