Thom Posted July 11, 2012 Report Share Posted July 11, 2012 Hi, While updating from firmware 4.8.9 to 4.9.3 I noticed that the calibration for the Bosch NTC ECT sensor had been corrected to Bosch's published calibration grid, but I'm still getting readings I suspect to be incorrect. On my engine the fans are triggered by a thermoswitch managed by a separate wiring harness, independant from the Vi-PEC. On the coolant circuit, this thermoswitch is plugged on the side of the radiator just besides the coolant inlet, about ~1m after the Bosch NTC sensor which is on the engine, besides the coolant outlet leading to the radiator. The thermoswitch triggers the fans at a temperature of 92°C. At this point, ECT in the Vi-PEC reads 100°C. I could understand a slight difference in temps, but losing 8°C over just 1 meter of coolant ducts/hoses that are not exposed to any flow of fresh air whatsoever sounds surreal to me. Unfortunately, I don't have a heat gun to measure the different points on the coolant line. -> Any idea why the difference is so large? Thanks. Quote Link to comment Share on other sites More sharing options...
lemmy01 Posted July 12, 2012 Report Share Posted July 12, 2012 Pull out the ect sensor and put him in cooking water.Only the sensor tip Better is if you have a calibrated thermometer but if you dont have one handy this works too. If you get readings over 100°C you calibration is off. Quote Link to comment Share on other sites More sharing options...
Scott Posted July 12, 2012 Report Share Posted July 12, 2012 Good morning, As lemmy suggests, you can remove your ECT sensor, extend the wiring so that you can put the sensor in a pot or bowl of boiling water and use an external thermometer to compare the reading you get in VTS with what your external thermometer reads. Scott Quote Link to comment Share on other sites More sharing options...
Thom Posted July 13, 2012 Author Report Share Posted July 13, 2012 Thanks but I already tested the sensor and it is within specs. Quote Link to comment Share on other sites More sharing options...
Jason Posted July 14, 2012 Report Share Posted July 14, 2012 so you've tested the sensor while it's connected to the vipec with an external thermometer and it reads correctly? Quote Link to comment Share on other sites More sharing options...
Thom Posted July 14, 2012 Author Report Share Posted July 14, 2012 The sensor reads correctly in function of the digital themometer and multimeter but it reads wrong in the Vi-PEC. Quote Link to comment Share on other sites More sharing options...
lemmy01 Posted July 14, 2012 Report Share Posted July 14, 2012 You could work out a calib for your sensor if you would have to solved it immediately. if you have a good thermometer for reference. Make a measure at 0,60 and 100/98 °C and interpolate the other values in the calib table. Than you should close enough. To have it very acurate you could make some more holds at 70 -90°C range. No big thing but you must have the sensor connect to the ecu and at best use the same wireing for calibration. Put both sensors in water move them and note the readings. But do not go to fast over the points it take some time to stabilize because of the different reaction time of the sensors Quote Link to comment Share on other sites More sharing options...
Thom Posted July 14, 2012 Author Report Share Posted July 14, 2012 I interpolated a new calibration table that may work fine. Just have to test it now. I will have to retry with the sensor in warm water to get more points than just two. Quote Link to comment Share on other sites More sharing options...
Sutkale Posted July 14, 2012 Report Share Posted July 14, 2012 Let us know where you end up with. I suspect the same problem, even though I see even larger difference. Quote Link to comment Share on other sites More sharing options...
Thom Posted July 14, 2012 Author Report Share Posted July 14, 2012 So I tried this calibration today and though I feel the results are closer to what they should be I think ECT now slightly underreads - my correction may be slightly excessive. Sutkale, care to share more details on what you are seeing? Interested to hear about other set ups. In my particular application the problem is that the coolant temp sensor is located in a "bypass" vein where coolant flow is highest when the thermostat is closed. When the thermostat opens, the waterpump then pulls most of the coolant out from the radiator and the flow in this vein should logically be lower than during the warm up period. As a result, it is possible that coolant may always read higher in this vein than in the rest of the engine... Quote Link to comment Share on other sites More sharing options...
Sutkale Posted July 15, 2012 Report Share Posted July 15, 2012 So I tried this calibration today and though I feel the results are closer to what they should be I think ECT now slightly underreads - my correction may be slightly excessive. Sutkale, care to share more details on what you are seeing? Interested to hear about other set ups. In my particular application the problem is that the coolant temp sensor is located in a "bypass" vein where coolant flow is highest when the thermostat is closed. When the thermostat opens, the waterpump then pulls most of the coolant out from the radiator and the flow in this vein should logically be lower than during the warm up period. As a result, it is possible that that coolant may always read higher in this vein than in the rest of the engine. Also, this vein is quite narrow, so if coolant doesn't flow through super fast then it may be getting heat-soaked by aluminium around it... Well, the heat gun showed 75 degrees while sensor showed 125 degrees. In reality the 75 is the real one since I have 78 degrees thermostat, very cold I know. Currently I am in the heat of making tests to my wiring harness due to another reasons but this problem is to be targeted also. However, the readings are correct while the engine is cold and this makes me think the firmware update has something to do with this. Quote Link to comment Share on other sites More sharing options...
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