The RPM input to the TCU is fed from the ECU. At the TCU the tach signal is:
......Yellow wire, pin 5, in a 12-pin black connector.
Come on, just go buy some resistors and try it
......worse that happens is it doesn't shift ..........just unplug the resistors and go back to stock.
What I'd recommend doing is getting a potentiometer as R2 and a highly precise R1 (10K) resistor. This way you can modify the input AC voltage to the TCU (given by r2). Just make sure you reading what the potentiometer is outputting.
Keep in mind another thing - voltage dividers are dependent on the input resistance of the system. Generally I'm assuming it's high, which it should be. But it might not. If it's close to the value of R2, or lower, this will have a bad effect and won't yield the desired output. Cut the yellow wire into the TCU and measure the resistance from yellow input to TCU to ground.
__________________
Mike - Proud owner of a Pearl 92 SVX LS-L 5MT with
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