Need help with 1227747 ECM and painless 60115 VSS w/TH400

[uncabob]

Hello from another Newby. Building a Rat-Rod from a 49 Jimmie with a 1982 XFI SBC 350 Corvette L83. Zero miles on rebuilt engine and TH400. Driving injectors with 1227747 ECM with AKAH chip and harness set up as dual truck injection system. Using original manifold and TBs plumbed in parallel instead of series so I could use matched truck injectors. I'm using an open drive line and a 94 Chevy PU axle with 3.42 gears. The tire radius is 29.5 inches (92.7 circumference). My question is how do I get speed data to the system. I have a DRAC with dip switches but I don't know how to get a ratio between .5 and .99. Painless says in their instructions to wire directly to the ECM. Doesn't the ECM need correct speed data? It is my understanding the VSS yields 2 Hz per rev. Has anyone used one of these?

[dave w]

Pin A10 on the computer is where one of the two wires from the Painless 60115 VSS is connected, the other VSS wire is connected to ground. The DRAC is NOT needed for the 1227747, if you have the Painless 60115 VSS wired like I describe.

dave w

[lionelhutz]

Once you wire directly to the ECM, you use the speedometer gears in the transmission to adjust the speed signal. If you have a mechanical speedometer that reads the correct speed, then the ECM will also be getting the correct signal.

A properly setup speedometer cable rotates 1000 revolutions per mile. That sensor gives 2 pulses per revolution. So, the ECM receives 2000 pulses per mile, just like it wants.

[uncabob]

That makes sense thanks gents.Bob