MoTec Head temp sensor
 

For those who are running MoTeC, are you running stock 12mm 993 head temp sensor? I have old school M48Pro.

I noticed on mine that my head temp was going up to appx 314F and basically flat lining. Something didn't seem right as I read posts of people getting up to 350F idling in warm weather.

So... Did a little test with sensor out of head and used torch to gradually bring up temp and see if it would go higher. Well it did not, gradual increased and then flat lined appx 314F

Have a new sensor coming to try, but figured I'd see what others are using.

I am using the stock 993 head temp sensor with a MoTec M150 and it works great. I’d have to look at the sensor setup in M1 Tune to tell you what was put there. But, I suspect that is of no help to you since you are using a gold box ECU.

Hi Joe
A sensor calibration is a sensor calibration and it doesn't matters which ECU you are using, X resistance means X temperature, and we just input the data for the x and y axis which are not linear by any means. Those sensors and the 3.2 L sensors peg at 396 F (don't change resistance w more temp). I did wonder how your head temps could only be 314 F when you shared that info a while back. Ping me and I will provide the table to input in your sensor calibration.


Kevin
GAS Motorsport

Thanks Kevin... Yea, I know not linear, though its close if you plot log scale. So you setup as a custom table? If I look at Bosch NTC (negative temp coeff) curve it 2.5k ohms at 20C.

I posted question on MoTeC forum also and got the data. Could only find values up to 150C on internet. If someone knows how to post files on this forum, let me know and I'll post it as it's a .pdf

Scott - On your M1 is it custom table or standard bosch sensor setup?

Cut and saved as pic. Here's data.



http://forums.pelicanparts.com/uploa...1730931509.jpg

Grabbed a breadboard (board used in hobby electronics), plugged in a potentiometer, parallel resistor and a voltmeter to simulate temp sensor resistance changes and fed it into the ECU to check and see what the "Bosch 2.5Ohm at 20C" setting and custom table above reads as far as temperature.

Readings taken in C from MoTeC and converted to F (as I relate better to that).

Up to 300F not bad, above that, major divergence. MoTeC did extrapolate as I was able to get reading above 392F. Need to get lower range potentiometer to check further.

What is a good dash setting for Head Temp "high" alarm value?

http://forums.pelicanparts.com/uploa...1731011831.jpg

Joe. Your graph doesn't look very much like the (yes custom) sensor calibration we use w that sensor ad the 3.2 L sensor , especially at the higher temp ranges.

Also I don't think I would use it to set an alarm as appropriate for low oil pressure or high Oil temp , but moreso use it to richen up the mixture and or reduce ignition timing when the heads particularly are getting really hot. These are avail as engine and ignition comp tables you should be able to base on Head temp. Again email me and i will give you the correct custom table to input.

One thing to note, the sensor pegs at 396 F, so if one is running a high boost Turbo engine and is above this range there is no backstop safety to add at say 425 or 500 F....Higher cylinder head temps means more risk of detonation... Another limit to our air cooled engines.

Kevin
GAS Motorsport

Not sure if the issue I'm having is related to what you guys are discussing here but curious whether this is the CAM sensor? I am having issues with my MoTec M84 on my 964 3.6L engine with RasantProducts intake. I had a local MoTec specialist look into my system because my rev limiter is firing in error at random time but mostly around 6000-6200RPM. It has occurred at lower RPM as well but inconsistently. Car runs very well other than this one issue. Wondering if any of you have run in to this problem before or have any thoughts on how to troubleshoot? My local MoTec specialist is suggesting trying to replace the CAM sensor with a new one in case its getting overheated.

This is "not" the cam sensor. We're discussing "head temperature" sensor. I've not had the issue you're mentioning and I'm not running cam sensor.

Plexiform - there are a whole bunch of threads on this forum related to that Rasant triggering deal packaged in a distributor housing and the problem that comes from a Hall sensor overheating and dropping out. From memory these have an operating temp window not to exceed 150-170 F, but learn which sensor they have installed in that assembly and look it up. You could try and utilize the advice of your Motec tech and change the sensor out , but if it is rated the same and inadequate, you're spinning your wheels. It would be important to distinguish between having the rev limiter initiated, vs running in to a synch error issue, and both and other conditions could be seen with proper logging set up.

Good luck
Kevin
GAS Motorsport

Thanks will look in to it.

For the heck of it it I contacted Bosch Motorsports to see if they had a temp sensor capable of higher temperatures... They did, link below. The price is (yikes) $500+, however was easily able to find 25C 10k ohms temp sensors similar for 10X less that.

https://www.bosch-motorsport.de/content/downloads/Raceparts/Resources/pdf/Data%20Sheet_70088843_Temperature_Sensor_NTC_M8-HS.pdf

This is quite a small sensor and without too much effort could be fitted for head temp sensing by using a hex 12mm plug drilled and tapped and fitting correct plug.

Below pic is shadow of the head of the Porsche head temp sensor (black) with Bosch sensor (blue) imposed over it.

http://forums.pelicanparts.com/uploa...1731763584.jpg

Would it standard CHT K type thermocouple work? I believe they have a pretty wide temp range, and are way cheaper than $500.

Yes a K type thermocouple is an excellent choice and can be fabricated in many different form factors to suite the install. This is my preferred method actually, and depending on the Thermocouple amplifier it will also be faster reacting than most other choices.

Only issue with this arrangement is that you would have to purchase another box if your engine management system does not have on board EGT inputs.

Has anyone possibly used this AIM CHT sensor?

https://www.pegasusautoracing.com/productdetails.asp?RecId=10721&utm_source=google&u tm_medium=cpc&utm_campaign=MC-035&srsltid=AfmBOoocoahvRm5Jz0d5R7vEQPoDWNV_tRvlU7 M4EMPmM-q1aW5PtpQDxZE

I started down the path of making a thermocouple sensor by mounted a TC in a 12x1 plug. Drilled hole in top and intersecting hole on side then punched in some lead BB sinkers to hold the TC in place, JB weld on top to hold wire coming out top. The AIM sensor seems simple. ...and made me think about routing TC wire out through plug hole vs up through shroud. Or maybe just mount an AIM 12mm CHT sensor under the 12x1 plug.

http://forums.pelicanparts.com/uploa...1735076853.jpg
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http://forums.pelicanparts.com/uploa...1735076927.jpg