COMPUSHIFT II Manual – COMPUSHIFT II Manual
Monitoring & Tuning Your System
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Transfer Case Ratio
1.00
4.2.10 Final Drive Ratio
Final drive ratio and tire diameter are used to calibrate the display's speedometer and dynamometer.
Set the final drive ratio in this screen.
Final Drive Ratio
4.11
4.2.11 Speedometer Calibration
Because many electronically-controlled transmissions lack the ability to drive a speedometer, your COMPUSHIFT II
has a feature to do so.
When you connect an electronic speedometer to the COMPUSHIFT II speedometer output signal, your speedometer
will expect a certain number of pulses per revolution (PPR) of the drive shaft, and you can adjust the PPR with this
setting.
If this value is set to 0.00, the controller will generate the same number of pulses per revolution as the transmission
output speed sensor (TOSS). This allows the speedometer output to generate a reproduced TOSS signal.
Speedometer
Calibration
4.00
4.2.12 Tire Diameter
Tire diameter and final drive ratio are needed to calibrate the display's speedometer and dynamometer.
The best way to measure the wheel diameter is by measuring the radius of the driven wheel, when the vehicle is on
the ground so you can take into account the flex (compression) in the tire.
Measure from the ground to the center of the wheel axle – double this number – and set the resulting diameter
value here.
Tire Diameter
HGM Automotive Electronics offers solutions for using an existing mechanical speedometer, if you have
one. More information can be obtained from your speedometer vendor or HGM.
