Here are a list of temp calibration files for different cars, files here are made for units with aref = 256 (standard since early 2006, see BuildProcedures/SectionThree)
Most installs best work with tempsensor_upload.bat 2252 2252 256
that is
- 2252 Ohm ntc type sensor for airtempsensor and
- 2252 Ohm ntc type sensor for coolant as well
Let's say
- your NTC (standard coolant, airtemp) sensor measures 4780 Ohm at +10C
- the 2252 Ohm sensor is 4481.5 Ohm at +10C (see diagram or table below)
- from this, calculate your sensor nominal resistance (at +25C) as 4780 / 4481.5 * 2252 = 2402 that is closest to pre-generated calibration curve of 2400 Ohm
Plotted with gnuplot using logarithmic Y-scale:
You can also interpolate using data below (for almighty precision):\n
Celsius Ohm -50 150394 -40 75780 -30 39860 -20 21860 -10 12460 0 7352.8 10 4481.5 20 2812.8 25 2252 30 1814.4 40 1199.6 50 811.4 60 560.3 70 394.55 80 282.63 90 206.13 100 152.75 110 114.92 120 87.671 130 67.770 140 52.983 150 41.881
If you have doubts, provide measurement(s) so we can help you select the best temperature curve. Actually with the common ntc type sensor, just one temperature point is sufficient (easiest with cold engine when sensor temperature is same as environment)
- sensor temperature
- sensor Ohm (when disconnected from ECM)
- sensor voltage (when connected to ECM, ECM powered up)
- LCD reading at that temp
- TerminalProgram Manmlp00mll command
- mostly useful if the firmware's vems.hex is known (or at least first 50 lines of vems.hex)
Coolant Sensors
| Car Make | Car model | Engine | sensor partno# | Pullup R | calibration file link |
| Volvo | 940 | B230FK | unknown | standard | [todo: clt.hex] |
Air Temp Sensors
| Car Make | Car model | Engine | sensor partno# | Pullup R | calibration file link |
| Volvo | 940 | B230FK | unknown | standard | [todo: iat.hex] |
| Audi | many 5cyl | AAN/ABY/ADU/3B/etc... | PTC type, appr 500 Ohm at roomtemp | 429..430 Ohm | [PTC_airdenfactor_430_Ohm_pullup.txt] |
Please make special .hex for BOSCH sensors. I believe this is most classical BOSCH NTC curve used from early 80s up to nowdays. No matter it is Volvo, Audi, Mercedes, Volksvagen, BMW etc - all of them had or have similar sensors.
Source: http://www.bosch-motorsport.de/pdf/sensors/temperature/NTC_M12.pdf
Both ...2063_256.hex and ...2252_256.hex give some degries mismatch at environment or engine operating temperatures. At tuning it is not heavy importance, but if LCD is used this is very welcome to see believable values on it.
Same isue had Miska Peippo described here: http://www.vems.hu/wiki/index.php?page=MembersPage%2FMiskaPeippo%2FAudiSSix