RPM limits of GM computer/ignition module?

[Andrew K. Mattei]

> 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.

In the "hmmm" department, in the LT1 PCM, the ALDL datastream RPM is maxed
at 6375, but the computer can certainly handle more, as in the transmission
datastream it uses more bits and will report the correct RPM value (I've
seen 6800 with transmission logging - oops! on a stock bottom end =8) dang
MPH shift points ;) ).

-Andrew

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