Turbo control in a GM ECM

[swagaero]

Ludis Langens wrote:
> 
> 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;}


remember  Detroit uses only 7# of boost with a vaccuum operated waste
gate The map is capable of 40#of boost with it's stock algorimith shim
the waste gate and you can go to almost ant boost the engine is capable
of within reason. All the ecm's from GM have the boost control written
in.

Steve
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