Reference Pulses, Time Between Reference Pulses, etc.

[84Elky]

Was thinking about this again when you replied and was about to make a correction, so will do it here. I made an error in both the value 1200 and what the variables represent. What’s really happening is a conversion of Distributor Reference Pulses (DRPs) at a given RPM to equivalent ECM clock ticks. Consider this:

4 DRPs        300 rev       1200 DRPs           1 min       20 DRPs
--------  x  ---------- = -------------- x -------------- = ----------
1 rev           min            min              60 sec        sec

Now, with 20 DRPs per second at 300 RPM, what’s the equivalent ECM pulse rate (in ECM clock ticks) at 300 RPM? It’s simply:

   65536 ECM Clock Ticks         1 sec                3277 ECM Clock Ticks
--------------------------  x  -------------    =  --------------------------
           sec                   20 DRPs              per DRP at 300 RPM

Perhaps that’s why it’s referred to in some of the comments as a “counter”.

I should have approached it this way to begin with using the above simple formula and it would have been much less complicated. And proving the formula:

1 sec         0.05 sec        1000000 uS
-------  =  ----------- x ------------------ = 50000uS per DRP at 300 RPM
20 DRPs        DRP               sec

 
3277 ECM Clock Ticks           15.26 uS
---------------------- x ------------------- = 50000uS per DRP at 300 RPM
per DRP at 300 RPM         ECM Clock Tick

Wish it weren’t so that it takes me so long to get somewhere. At times it takes a while for the synapses to fire..

[1project2many]

ANHT is essentially someone's personal notebook. Not all of the notes are meaningful and some are not 100% correct. I haven't looked at AUJP lately but I think that contains some of the same comments and possibly some of the same errors.

Feel free to challenge what's presented. Several months ago there was a long thread that started as a question about EGR operation, moved through the discovery that the temperature conversion we'd been taking for granted was not correct for all ecm's, and ended with development of a polynomial representation of a thermistor lookup table for use in some ADX files. Wouldn't have happened without someone asking questions.