Originally Posted By: OilUzer
Don't know your exact setup ... short of having your own sensors, can you integrate coolant temp and IAT from OBD II? With some cars you can also read outside air temp. I can with one of our cars.
Pulling data from OBD II will be tough since I already have a Scanguage hooked up for fuel economy display and reading trouble codes. I do have ideas about reading sensors in parallel, since the car uses 5 volts and shared ground just like my Arduino.
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If not, IAT typically tracks ambient temp if the car is moving. Based on my experience with 3 different cars, IAT is about 6°F to 12°F higher than outside temp. and with one car, I consistently read about 10°F above ambient temp. In both cases and for obvious reason, the car has to be moving at a relatively good speed and for a relatively extended period of time after a long idle. For example if you are in stop and go, IAF could get as high as 40-50F or more above the outside temp!
IAT is strange on my car, as it seems to read a few degrees
lower on OBD II compared to the ambient temp. It did the same thing before and after a MAF replacement so not sure what's happening there.
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Effects of higher ambient temp on oil and coolant temp. is not linear. e.g. If outside temp is 50F higher from one test to another, don't expect the coolant and/or oil temp. to follow.
@shannow recently had a link in one of his post to another one of his old threads (i call it the facy curve thread) talking about this ...
Very cool! One of the reasons why I love this forum.
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Based on my experience/data, i have noticed minimal (but not 0) impact. don't have my excel sheets in front of me but if I recall correctly, i have bunch of data @ 40°F and lower in winter vs. 80F and higher in summer and the max coolant temp. observed in summer was only 5-8°F higher going up the same steep hill. If the car was moving on flats, maybe 5F difference max.
Sounds about right if the cooling system is in good shape and the vehicle isn't overloaded. Mine didn't get much hotter even when climbing a grade in 110 degree southwest heat last summer.
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I can read my trans temp (TC and Pan) but don't have ways to track the engine oil temp. it is under to do list for one of the cars mainly out of curiosity but it should track the coolant temp closely (+15°F to +40°F ?? Depending on the car)...
It should run lower than coolant temp. Transmissions aren't happy running too hot, so +15 to +40 compared to coolant would fry the transmission in short order. Before I added an external cooler, mine ran 10+ degrees below coolant temp unless I was pushing it. Now with cooler, transmission thermostat, and extra fan control, I've never seen it more than 94C / 201F even when working hard.
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basically I observed minimal (5F-8°F) difference in coolant temp with respect to ~45°F difference in ambient temp. However have a feeling that ambient temp may have more impact (>5-8°F) on the oil temp. than it has on the coolant temperature. Maybe more instantaneous difference ... hence one of my to do list of reading the oil temp
But it all depends on where the data is collected and so many other variables ...
Yeah. I'm interested to see what happens there. My oil is thermostatically controlled, so that may behave closer to the coolant instead since the hotter it gets the more cooling capacity opens up.