I want to modify my TPS. Adjustment of this unit is too difficult, too imprecise and mine appears to vary over time slightly.

My plan is to raise the TPS setting to about 1V above the prescribed voltage and add a modern trim potentiometer and 2V meter to the circuit. This way I can easily adjust the voltage to spec. The TPS will function as normal but with it's resistance slightly augmented by the pot.

What I would like to do is order the correct ranged potentiometer. Does anyone here know how to spec a pot to a 12V system that would give me a 1-2V variance? If not, I suppose I can always pick up a range of them and do some science on it.

Edit: I guess I can change the setting on the TPS to be 1.34V, meter the TPS ohms, reset it and re-meter the ohms, take the difference and get a potentiometer that provides approximately double that resistance.

 

If useing a digital multimeter while adjusting Tps try using an analog meter adjustment want be as sensitive

 

The way the TPS works is a voltage divider, the ECU input will provide the fixed side of the divider R2.

The equation to work out the voltage is.

Vout = Vin*(R2/R1+R2) so R1= Vout / (Vin*R2 - Vout *R2)

Where R1 is the TPS and R2 can be your trim pot.

SO lets put some nominal values
R2 = 10ohms
Vin = 12volts
Vout = 2volts

R1 = 2 / (12*10 - 2*10)
R1 = 2/ 100
R1 = 50ohms

To complicate things, if you put a trim pot it will be in parallel with the ECU R2 so these resistances add like this R2trim and R2ecu

R2total would be this 1/R2total = 1/R2tim+ 1/R2ecu

So you can see if you double the pot resistance it will not double Vout.

I know this can be confusing, this is why an electronics qualification takes years.

Hope this helps

 

Warren,

This is great! Thanks for the electronics lesson. I'll let you know how it works out!