Caterham temp sensor calibration info needed

[JohnCh]

I know this is a longshot, does anyone know the calibration data for the temperature sensor Caterham uses for the coolant gauge and oil temperature?  (parts store link here)  I need this data to configure the AiM dash to accurately display oil temperature.

 

Apparently, it's a very common sensor used by a number of different car manufacturers and made by several sensor companies under the generic part number MD091056, but no one seems to publish any of the data. I've already checked with both US and UK AiM support, a few Caterham specialists who install AiM dashes, and sensor manufacturers without success.  

 

When testing the resistance output at a few temperatures between freezing and boiling, it became clear this is not a linear output, which means mapping it myself with any accuracy isn't really an option.

 

Thanks,

John

[ashyers]

John,

Is it possible to cross it to a Bosch sensor? If so it's easy to find info on those.

 

Andy

[MV8]

Too bad you don't have the gauges. It would be easy to be build a table with a potentiometer based on indication. If it is programmable, why use a sensor you can't get specs on?

[JohnCh]

I've searched for a Bosch cross-reference using some of the more common manufacturer's specific part numbers, but no luck that way.  I'll see if have better luck searching for Bosch replacements using some of the car models that use the sensor.  BTW this is one of the lists I've found:  https://www.autodoc.co.uk/car-parts/oem/md091056  

 

Switching sensors may be the final solution, but I first want to exhaust other possibilities.  That sensor came with the car and consequently is plug and play from a wiring perspective; a simple one wire connection with the ground through the body.  I like that simplicity.  I also didn't realize getting the sensor data would be so hard.

 

I hadn't considered building the map via the gauge.  Great idea.  I have that sitting on a shelf.  I'll look into that option as well.

 

Thanks,

John

[sf4018]

It's an 8 bit unsigned integer, 0 (0v) = -30C, 256 (5v) = 130C. If you have the SBD ECU  have a CAN protocol for Aim RS3 if you want it (I think I modified it some on the ECU side but it's a reference at least).

[JohnCh]

Thanks @sf4018.  Are you using the 9A9 or 9A4?  I'm using the latter, and have CAN enabled for the 420R native outputs (ECT, RPM, and Battery) but the oil temp sensor isn't wired into the MBE so nothing to output.  

 

I just did a search and found that AEM makes a sensor that will work and includes a very detailed resistance to temperature chart.  For $50, that might be the easiest path forward.

[sf4018]

I have the 9A4. Attached is the Race Studio 3 .xc1 file and the pinout for the ECU if you want to hook the temp sensor up to some spare IO. The CAN output from the ECU is programmable so it is possible to add any sensor to it.

MBE9A4-PinoutIssue_F.pdf

Caterham_420R New ECU_@20210824_224149_008622.xc1

Cheers,

Simon

[JohnCh]

Thanks!  I'll take a look at this when meeting hell dies down.   

[sltous]

Hi @JohnCh did you end up finding calibration data for this temp sensor?  I've just fitted a Caterham 71167 sensor to my oil sump and was hoping to wire it to an AIM system for logging.  My ECU outputs water temperature from the other water temperature sensor, I believe it is the Coolant Water Elbow to ECU part number PR6895, while the Caterham 71167 senders for oil and for water go only to the dashboard gauge via a dashboard switch.  I have looked at the temperature sensor section of your custom CAN @sf4018 and I think I could maybe learn how to turn that into a custom sensor if I really had my back up against the wall but it would take some learning.

 

I think I am seeing one possible source here: https://www.caterhamlotus7.club/forum/techtalk/k-series-temppress-sensor-details which may be worth trying.  I do have the luxury of the submarine Caterham 71167 sensor being fitted within about 3 inches of the Coolant Water Elbow to ECU part number PR6895 so I could likely correlate the two sensors and get confirmation relatively easily

Edited August 16, 2023 by sltous

[JohnCh]

Someone suggested to use this Bosch sensor calibration.  https://www.bosch-motorsport.com/content/downloads/Raceparts/Resources/pdf/Data Sheet_70101387_Temperature_Sensor_NTC_M12.pdf .  I went with the RaceStudio suggestion of 2700 ohms for the pull-up resistor.

 

I haven't yet confirmed the accuracy at operating temps, but measuring the oil in the dry sump tank with an infrared temperature sensor showed the dash reading was only off by about 4C with the temps in the low 60C range.   

[sltous]

Thanks John.  I did a quick plot compared with the Revilla data from above and they look similar although there is not a fixed offset.  I'll probably end up trying each one and hope to get something close enough to be useful.  

 

Temp C	Difference (ohms) Bosch is higher
50	210
60	174
70	153
80	132
90	115
100	102