I have just finished installing megasquirt on my 4G63-T and the revcounter does not get any signal. Where does the rev gauges normal get the signal?
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gtluke
Well-known member
the negative side of the coil is traditionally where you get the tach signal. there may be a better place specific to our cars, hopefully someone will chime in withe answer.
stevep
Well-known member
The ECU gets it RPM data from the CAS signals. It also gets a ignition pulse from the coil pack (pre-91) or the power transistor (91+) that is also used to drive the factory tach.
Steve
Steve
The ECU has it's tach signal but my revcounter in the dashboard does not get any signal - where should I connect my wire on the engine?
As SteveP above said, it depends whether you have the 1990-style coilpack and transistor, or the 1991+ style. The newer, 7-pin transistor has an extra "TAC" connection that pulls to ground everytime a coil fires. The 1990-style has a separate "TACH DRIVER" module attached to the coilpack that pulls the line to +12 volts everytime a coil fires. The ECU rpm signal is derived from the CAS signals, not the tach pulses.
