Flywheel/Encoder patterns

[Jeffrey Engel]

Mazda Ebrahimi <kleenair at ix.netcom.com wrote:

> Jeffrey Engel wrote:
> > 
> > > Subject:       Re: Flywheel/Encoder patterns
> > > From:          Kalle Pihlajasaari <kalle at device.data.co.za>
> > 
> > > Hi There,
> >
> > An encoder giving absolute crank position would implicitly supply an
> > interrupt when the position changes value. Reading crank position directly
> > means you wouldn't have to fool with timers or counters to derive it. You'd
> > also know exactly what the position is upon start-up without having to store
> > the last known position info upon shutdown. No way around the cam sensor tho
> > that I can see.
> 
> The only real world advatage I see to the encoder is quicker starting with lower 
> emissions.  Updating the degree count takes very little time in the processor.  We still 
> have to employ a timer to calculate RPM, right?
> 
Actually, the above is far too sage to have been written by me.  I 
got into this discussion by remarking that Grumpy Jenkins found 
enough crank flex (at 650+ HP) to make sub-degree measurements 
useless.   Of course he had to deal with crank AND cam flex because 
the distributor is at the back of the engine.

Someone a while back made the point that burning is a function of 
time, not crank angle.  Would it be practical to find TDC of the 
cylinders and use a time offset?

je
jengel at fastlane.net