User manual

GPX Pro 36
© 2009 XT Racing
12-V peak-to-peak signal. You might also use a one of the fuel-injector outputs of the ECU as the
RPM input.
NOTE: Direct connection is the most accurate and reliable method
of determining RPM.
To utilize “direct” mode, connect the GREEN WIRE OF CABLE “A” (digital input # 5) or the BROWN
WIRE OF CABLE “A” (analog/digital input # 1) to the to the vehicle’s digital tach signal.
If your vehicle has no such signal, you can use the “coupled” method. This is accomplished by
wrapping an insulated wire (preferable 22-24 gauge wire) around a spark plug wire about 4-7
times and connecting that to the appropriate input on the GPX. You can check if the coupled pick-
up is working correctly by looking at the RPM indication on the main screen. If it is not picking up
properly, you can try a few more wraps of the wire around the spark plug wire until the RPM gets
picked up reliably.
Once the pickup is working correctly, apply a few wraps of electrical tape over the coiled wire to
hold it in place.
To utilize “coupled” (inductive) pickup mode, connect the BLUE WIRE OF CABLE “A” to the
wrapped wire around the spark plug wire.
Both types of RPM, direct or coupled, 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: