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Potential Tuner
Speedometer setup E38 LY2 in 72'C20 plus alternator mystery
Hi - brand new here.
I am almost done with a swap of an 09' LY2 4.8 engine and 4L60E trans into a 1972 Chevy C20. It is starting and running and driving well at this point. There are a few things that I am trying to sort out to finish it off. Rear end is 3.73 ratio, tires are 30.5" diameter. I've added a pin at 57 in X1 to supply the speedometer signal to the gauge.
The main issue is the speedometer is off, reading more than double from what it should be reading. The speedo is a swap from an 80's S10 and is electronic. From what I understand, it expects a 4000PPM signal. I can't determine how to set this up in the current HP editor. The settings I have under the Speedo section are:
HARDWARE
Speed Output Type: VehRepTOS
VSS Pulses Per Rev: 149 (I arrived at this by 40 x 3.73) had previously tried 4000 but it read way low
ISS Pulses Per Rev: 30
VSS Pulses Per Rev - Trans: 40
VEHICLE SPEED SENSOR
Vehicle Speed Output: RepTOS
Pulse Average: 11
Max period: 30
Serial Min Freq: 1Hz
WHEEL SPEED SENSOR
Wheel speed output: Enabled
Pulse average: 1
Max period: 30
FINAL DRIVE
Ratio: 3.73
Ratio Error: 3.73
Trans: 3.73
VSS TIRE REVS PER
Dist: 662 miles
Dist Err: 410 miles
Dist trans: 662 miles
Any ideas about setting this up properly would be great. I was going to try values above 149 and see if the speedo ends up close, but that doesn't seem like the best approach vs actually doing the math.
The other mystery is that the alternator is only outputting 13.8V and even when I tried sending a PWM 5V, 128Hz, varied duty % signal to it, I can't get it to change. Even with the alternator disconnected it is the same 13.8v which I know is a default value. I have the battery current sensor but don't know what I could connect it to in order to have the variable alternator output that is possible with this engine and computer. I changed the Alternator settings under System to:
Voltage control: not fitted
ECM override: disabled
Any help would be great to get it all dialed in!
Derek