VSS ?

["K.E. Towle" <karljiml@compuserve.com>]

Scott,

>Does anyone have information / experience with the pros and cons of not 
having a VSS on a TBI system using the1227747 ECU?  I have heard from some 
that say you need it; others say you don't.

In the event VSS needs to come to a car near me, does anyone know many 
pulses per MPH are required for this system?<

Never tried to run my 747 ECM without VSS, but I sure had fun verifying I
had the proper signal to it. Book says it needs a signal of 2000 pulses per
mile (PPM), but I confess I don't know if that number could be dependant on
the PROM installed. Anyway, I do know that the cruise control on the 84 G20
van just happens to need 2000 PPM, and it gets it from a small module
mounted on the back of the mechanical speedometer. I also know that the 747
ECM is happy with this same signal supplied to it. I've talked to one guy
who cut up an old speedometer, extracted the components necessary to
generate the signal, and then installed them just behind the stock
speedometer. Speedo cable connected to VSS parts, which then turned the
speedo.  It sounded slightly kludged, and very dependent on available
space, but it solved his need for VSS.
Karl
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