Asynchronous injection (and PLD)

[Walter Sherwin]

Or, when the high rev WOT SYNCH TBI pulses are too long versus the available
REF pulse logic headroom...........

Walt.



>
> Generally yes. On a tbi ecm gm set it up to use async pulses for an
> accel
> enrichment. They sputter asynchronously between the normal sync pulses.
>
> The other time async is used, is when the sync pulses get so short that
> they can not meter fuel accurately enough. The ecm will switch to async
> pulses until the required sync pulses are large enough again.
>
> BobR.
>
>
> Jeroen Proveniers wrote:
>
> > Hello,
> >
> > is asynchronous firing of the injectors necessary, except when starting?
> >
> > I'm currently investigating the use of a PLD (Altera MAX7000S) to
implement
> > all the timing logic for injection and ignition, so when async firing is
an
> > absolute requirement I've to account for it.
> >
> > Short description of the PLD:
> > The PLD is aimed at sequential injection. Synchronisation to the engine
is
> > by 2 sensors at the camshaft. Injection start can be controlled by the
main
> > controller. In fact, sensor one gives 60 pulses per revolution that
> > decrements a counter, while the other sensor resets the counter to a
> > predefined value (reset value). When the counter is at zero it's
reloaded
> > with the reload value at the next pulse. At terminal count an other
counter
> > is kicked that selects the injector, and injection is then started by
> > kicking a oneshot timer (16 bits, clocked at 1MHz).
> >
> > So injection starttime can be controlled by changing the reset value.
The
> > reload value is fixed as it defines the number of cylinders.
> > I'm also thinking about stopping injection when intake valves close,
instead
> > of starting injection when the valve opens.
> >
> > JJ
> >
>
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