Turbo control in a GM ECM

[Shannen Durphey]

----------
> 
> 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.

Turbocharged?? I coulda' been a contender.
> 
> >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?  :-)

Yup.  Diesels have no natural vacuum.  GM uses a pump on the front to
supply it to the wastegate sol.

> >Boost is measured by a map sensor.
> 
> Yup.  And it also "runs" the engine.
> 
Not on this app.  TPS is in gas pedal (Accelerator Pedal Position), no
throttle cable, stepper motor operates injection pump, fuel is delivered
based on APP and RPM.  

> >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;}
>