User manual

GPX Pro 40

which is a pulsed, binary logic signal which is typically generated by the vehicle’s engine control

unit/module (ECU or ECM). Most fuel-injected engines will have such a signal available. The

signal can be as low as a 3.3-volt peak-to-peak signal, or as high as a 12-V peak-to-peak signal. You

might also use a one of the fuel-injector outputs of the ECU as the RPM input.

You may need to have the reported rpm either multiplied or divided by 2, 3, or 4. For example,

the engine might be running at 1000 rpm, but only 500 rpm are showing on the screen. In this case

the input would need to be multiplied by 2. Whether or not this is required depends on the

number of cylinders, 2- or 4-cycle engine, and type of signal you are monitoring.

To set the multiplier or divider, go to the Cal column of the RPM input and press Select:

Then, use the arrows to make your choice, and press Select:

1.8.3.3 Throttle Position

Throttle position needs two points for calibration -- the 0% throttle position (no throttle applied)

and the 100% throttle position (throttle completely applied). On most vehicles, you should do

this calibration while the vehicle is turned on, but not running (it might not be a good idea to run

full throttle in neutral!).

1.8.3.4 Temperature

Most vehicle temperature sensor are thermistors (resistors which vary resistance depending on

their temperature). These sensors need to be calibrated within the GPX at several different