Quote:
Originally posted by rmjjensen
If you want to simply change the tach rate that the TCU sees you can use a voltage divider circuit for the TCU's tach signal.
The voltage divider circuit consists of two resistors and will work on both AC and DC signals. You just need to use the divider circuit and use that as the reference tach signal into the TCU.
So - currently, the voltage @ 6500RPM will be at the maximum, but you'd like to change it so the maximum is actually 7000RPM.
6500/7000 = 0.92857 <- Ratio
So, our voltage divider circuit needs to have this ratio.
...Vin(R2/R1+R2) is a basic voltage divider.
so, R2/(R1+R2) = 0.92857
..........we want a high impedance to draw low current, so let's just make R2 = 10k ohms
Simplifying the equations yields R1 = 769.23
Bang .......get a 10K ohm resistor and a 770 Ohm and you have a perfect voltage divider circuit that WILL trick the rev limiter.
But - before you get into this you have to determine if the RPMS vs Voltage is a linear plot. If it is not, then this circuit is useless 
|
Thanks for the thorough explanation... That's my current plan.
Determining what the RPMs are vs. the voltage is the next step, and which is why I need to find a way to hookup my multimeter to the ECU>TCU RPM feed.