RPM limits of GM computer/ignition module?

[Nick McAlpin]

Any chance of playing that game of space invaders on the CPU 
you pull out?  =)

on a more serious note: is it true of older ECM's (like the 88 P4 i 
am working on) that they also update hardware and the hardware 
fires the injector/ignition?  and when you say "older" ECM's are 
255x25rpm - would that also apply to the P4?

thanks!
nick

> The hardware in the PCM should be able to keep up at an RPM way higher
> than a street engine will achieve.  Firing the injectors and ignition is
> handled by hardware.  The software simply updates the hardware timers to
> match new sensor conditions 80 or so times a second.  You could pull
> onto a freeway in Kansas, get up to speed, throw a brick on the
> throttle, pull the CPU out, and play space invaders until you reach your exit.
> 
> On the software side though, there can be a maximum RPM in the ECM's
> calculations.  In older ECMs, the limit is 6375 RPM (255 x 25 RPM). 
> Anything higher will be calculated as 6375.  Reports are that this
> creates a soft rev limiter.  The software for a few applications uses
> different scaling to go a bit higher.  For example, the 3.4 DOHC bumps
> the limit to 7150 RPM.

----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org