Turbo control in a GM ECM

[Jeffrey Engel]

Are you guys sure that vaccuum is used to actuate the wastegate?  
It's possible I'm sure, but under boost there's pressure and more of 
it until the 'gate needs to open up.  Sure would seem logical to use 
pressure.  Of course, we are talking about GM here. . .

==========================================
> Date:          Thu, 23 Oct 1997 03:04:22 -0700 (PDT)
> From:          Ludis Langens <ludis at netcom.com>
> To:            diy_efi at coulomb.eng.ohio-state.edu
> Subject:       Re: Turbo control in a GM ECM
> Reply-to:      diy_efi at coulomb.eng.ohio-state.edu

> Shannen Durphey <shannen at mcn.net> wrote:
> > > 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.
> 
> The 2.8 MPFI V6 is a gasoline engine.  What I was getting at is: when the
> turbo is running, and the throttle is quite open, there shouldn't be any
> vacuum anywhere in the intake or exhaust system.  Of course, for a wastegate,
> all that matters is relative vacuum.
> 
> > > >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.  
> 
> As I said, this engine is gasoline engine and it is a MAP (as opposed to a
> MAF) system.  I can say with 100% confidence that the absolute position of
> the accelerator (via the TPS) is never used to control fuel delivery.  (Unless
> the MAP sensor is broken and a substitute MAP is being computed from the TPS.)
> Short term relative changes in the TPS do affect the fuel delivery - but I'm
> still chasing after those.
> 
>                    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;}
> 
> 
je
jengel at fastlane.net

     "I can resist anything but temptation"
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