speedo signal specs

[Robert W. Hughes]

> I've got a '94 Z28 w/6-speed. the pcm is calibrated for 3.42 gears and i
> have 3.73s. i'm wanting to convert the signal from the pcm to the dash to
> compensate for the gears. I'm planning on using the freq-to-volt change volt
> volt-to-freq type of circuit. my question is, has anyone scoped this signal?
> i know the pcm puts out 4000 pulses per mile but is it a 0 - 5 volt square
> wave? 0-12V? My car isn't driveable right now so i can't check it out on
> mine. How sensitive is the speedo to its input? does the duty cycle of the
> wave matter or is it just triggering off of rising edges per second?

You probably need to check this out:
ftp://ftp.diy-efi.org/incoming/DRAC2.pdf
-- 
Robert W. Hughes (Bob)
BackYard Engineering
29:40.237N, 95:28.726W
Houston, Texas "The city with too much Oxygen"
rwhughe at ev1.net
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