DRAC for 730 to 749 conversion

[Ludis Langens]

Dan Plaskett wrote:
> 
> In changing from 730 ECM running 1991 Corvette AXCN code to 749 ECM running
> SyTy code I've run into a couple of questions.
> 
> First, in the Corvette code there are two VSS inputs high and low that run
> from the VSS sensor mounted on the transmission.  The Pinout diagram for the
> SyTy does not use VSS inputs but instead uses a DRAC signal on pin C6.
> After searching and reading the archives my conclusion is that I need to
> obtain the DRAC to get the vehicle speed information into the ECM.  I am
> running a mechanical speedo so I am not really concerned about the VSS
> outputs that normally drive the speedo but it seems that I still need the
> DRAC.

No, you don't need a DRAC (assuming you have everything working with the
730.)  All you need to do is flip the bit in the SyTy PROM image that
tells it to use the "high and low" VSS inputs instead.  You might also
have to change a few calibration constants that the ECM uses to convert
the VSS inputs to MPH.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
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