Originally Posted by AbeFM
Rev: I know you're a data-intensive kinda guy....
Did you ever check to make sure these were right? I tried a few numbers people told me, and they never worked right on my car. I went as far as slipping a thermocouple under the house in the housing where the temp sensor is.... But I'm getting more interested in trying it again.
I always log my way through what I do, so:
1) Measurements were taken on the 11th of July, 2006, 17:50.
2) Ambient temperature at that time was 30C (86F).
3) I moved the car from the parking lot at work to take it about half a mile away, to a friend's garage, maybe less.
4) With the car parked, I measured the resistance of both sensors, and logged both values against what the OBD-II said.
5) IAT was 1550 Ohms, Vout at the divider was 1.82V. Bias resistor is Rb=1550 * (5-1.82)/1.82 = 1550 * 1.75 = 2713 Ohms
5) CLT was 1330 Ohms, Vout at the divider was 2.31V. Bias resistor is Rb=1330 * (5-2.31)/2.31 = 1330 * 1.165 = 1550 Ohms
6) For the above calculations, the formula is Vout = (Vin*Rt)/(Rb+Rt)
7) Three distinct datasets were taken for each sensor. For coolant, 20C, 40C and 80C. For air temp, 20C, 40C, 65C. Values were 2491, 2177 and 317 for CLT, 2499, 2165 and 498 for IAT.
8) Solving the Steinhart-Hart equation (1/T = A + B(ln(R)) + C(ln(R))^3) for the datasets above, the results are:
CLT: A=1.193449*10^-03 B=2.837733*10^-04 C= 6.840434*10^-09
IAT: A=1.193449*10^-03 B=2.837733*10^-04 C= 6.840434*10^-09 (Surprise, surprise)
I've used the above settings on my parallel MS1 with excellent results. The same sensors are used on 89-95 RX-7s, these same settings I also used on LogWorks with an LMA-2 to read the CLT/IAT on that car and matched the settings as displayed by the Datalogit software of the PowerFC ECU.
Ps. Yes, they ******* work, noob!