correct value for warm CHT reading (ohms) Options

[brant]

so my CHT reading was 76 ohms - hot (at 180F oil temp)
I'm reading 2 different things.. on the Brad anders site


one saying that a warm reading should be below 100 ohms
but then the table shows this: for 210F

Sensor Temp = 39 deg. F Temp = 61 deg. F Temp = 210 deg F

0 280 130 003 6.10 K ohms 2.94 K ohms 199.3 ohms
0 280 130 012 NA 2.85 K ohms 191.2 ohms
0 280 130 017 3.63 K ohms 1.74 K ohms 124.7 ohms



I'd love some input from Djet folks about what numbers you see on a warm motor?

brant

[JamesM]

so my CHT reading was 76 ohms - hot (at 180F oil temp)
I'm reading 2 different things.. on the Brad anders site


one saying that a warm reading should be below 100 ohms
but then the table shows this: for 210F

Sensor Temp = 39 deg. F Temp = 61 deg. F Temp = 210 deg F

0 280 130 003 6.10 K ohms 2.94 K ohms 199.3 ohms
0 280 130 012 NA 2.85 K ohms 191.2 ohms
0 280 130 017 3.63 K ohms 1.74 K ohms 124.7 ohms



I'd love some input from Djet folks about what numbers you see on a warm motor?

brant

I believe the discrepancy may be due to (among other things) what can be easily measured on the bench vs installed in a car. The 210 readings were provided because that is a temp point that can easily be measured with the sensor off the car using boiling water

however:

1. The sensor resistance curve doesn't stop at 210 degrees
and
2. Our heads get a lot hotter than 210 degrees in practice.

So take a resistance reading off a sensor installed in a car on a fully warmed motor you are most likely going to see less resistance than the stated 210 deg value, and is going to vary a bit depending on the current temp of the motor.

Also, not sure what the factory tolerance was but I have always seen some level of variance when measuring both CHT and MPS sensors (the two main influencing variables on mixture for d-jet) even across identical part numbers.

Another point of note is that with a single wire sensor the ultimate reading is also dependent on the resistance over the motors ground path which can vary while the car is in operation.

I didnt hang on to the data but I measured every CHT and MPS from my collection with Eric to get baseline data when PMB was putting together their MPS rebuild program, the results were interesting...

They install modern ECUs now (IMG:style_emoticons/default/biggrin.gif)

Bottom line, if you want consistently accurate fueling go with a modern setup.