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  #16  
Old 02-03-2005, 08:19 AM
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rmjjensen rmjjensen is offline
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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.
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  #17  
Old 02-03-2005, 04:03 PM
oab_au oab_au is offline
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The problem is, we don't know for sure, what form the signal is.

The signal that the ECU receives from the crank sensor is pulsed. I would think it is still a pulsed signal that the TCU receives.

To change it to a varing voltage, they would need a 'digtal to analog' converter in the ECU, and a 'A to D ' converter in the TCU, to turn it back to digtal, to be processed. This is unlikely due to the extra circuitry needed, and the interferance that a varing voltage would be subjected to.

Never the less, the pulsed signal can be divided down by a Cemos flip flop, or a divide by two counter. This will change the count to half the value, so that the TCU never sees the engine rpm change point, and it will run up to the engine rev limiter.

Harvey.
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