Changing injector pulse rate at idle?

[John T Stein]

Robert Dingli wrote,
> 
> The simple solution would be that 5mS is the limit of your system's 
> resolution (as some earlier has pointed out).  
> 
> From my research into crank speed measurements, it is not unusual to
> observe repeatable cyclic crank speed fluctuations, but as mentioned,
> one would expect to observed periods other than exactly 40 or 45 mS.
> What is the resolution of your measuring device?
> 
> Robert


Robert,

I made my measurements with an oscilloscope triggered on the injector 
pulse itself, so the time  resolution of the measurement is not a 
limit.

The explanation offered earlier by Michael Sargent and to which you 
referred  is appealing.  ASSUMING the engine controller has a 
"hold off" counter which delays the injector pulse by a specific 
crank angle after the crank signal, a slight jitter in the crank period 
COULD cause the controller to change the TIME delay introduced by
the "hold off" counter in an effort to keep the delay ANGLE constant.  
If the LSB of the counter were to be 5 milliseconds.... 

The question is, is such a "hold-off" counter typically used"??

Thanks for the comments,

John