I have a 90-94 ‘real’ oil pressure sender but no real oil pressure gauge in my S2000 cluster, so I’m using the MS3X to trigger my oil warning light at a preset value.
The wire coming from the sensor no longer goes to the instrument cluster but to the MS3X on port ADC13 instead. Since the oil pressure sender outputs no voltage (it’s a simple lineair resistor), a bias resistor is added on the MS3X card in the R67 position. The oil pressure sender has a fairly low resistance so I used 330ohm to get good accuracy. Worst case, this pulls about 15mA through the sensor so it shouldn’t be a problem.
The factory manual mentions these resistor values:
0psi => 52 ohms
90psi => 16 ohms
With a 330 ohm bias resistor we can calculate the corresponding input voltage on ADC13:
0psi => 5*52/(52+330) = 0.68V
90psi => 5*16/(16+330) = 0.23V
With this we can calculate the 0V and 5V values in Tunerstudio:
0V => (90-0)/(0.23-0.68)*(0-0.68) = 136
5V => (90-0)/(0.23-0.68)*(5-0.68) = -864
Enter these values in Generic Sensor Input 1
sensor – source: Spare ADC (ADC13)
Transformation: Linear mode
Now you can use a spare output port to trigger the oil warning light when oil pressure goes below 15psi. I use these values:
Output port IAC2
Power on value: 1
Trigger value: 0
Output channel: sensor01 < 15 Hysteresis 2
If you have a real oil pressure gauge, you probably want keep using it (no point in disconnecting a perfectly good oil pressure gauge!). You’d obviously need no bias resistor and you need to make sure you do NOT send over 5V into the ADC port. The gauge works with 12V, so it’s probable that you measure more then 5V over the oil pressure sender (I never checked though). If so, you’ll have to use a voltage divider to bring it down to 5V.
Obviously, you’ll have to do some math since you’re now using an unknown bias resistor (easy to calculate its value).
