Is the degree/volt output of these sensors linear for the entire temp range? I have a 2 deg F difference after a 12+ hr cold soak and was wondering if I can use a constant 2 deg offset or if I have to apply some other scaling factor to get a better idea of my deltas at 190 deg.

 

2 degrees at 190 is basically 1%. The accuracy of the sensor at that temp is probably 2% - 3%, that's about all those sensors and the interface on the computer that converts that voltage into digital data can achieve. Also, if you have the X-gauge programmed for ECT it only reads in 2 degree increments. So basically ignore the offset, you are about as close as the technology allows. I had to learn the difference between accuracy and precision in electronics school, you would be failed if you reported a reading that was more precise than the measuring tool allowed for accuracy.

If at cold soak the actual temp was exactly 31.3 degrees and the sensors are accurate to 2%, your ECT could with complete accuracy report that as 30 degrees and your EOT could with complete accuracy report that as 32 degrees. I would just watch the numbers you have, get a sense of what they are in different operating conditions and as long as they are OK now just be alert for a change. It's the change over time that tells you that there is a problem starting to rear it's ugly head.

 

I have been using the Torque app with a bluetooth OBDII connector to monitor the truck. It seems like the resolution is .2 degrees. It seems that if I was hovering near the 15-16 deg mark I may want to be concened but as I am running closer to 10-11 degrees I really don't need to be concerned to much. Another question about the deltas, if in cold weather is there a max oil temp I should be considering. The 10-11 degree deltas seem to be only when the thermostat opens and the ECT drops down to 186 for a minute or so.

 

Sorry, i was too Scangauge- centric there. But still - the precision might be 0.2 degrees, but that will not be the accuracy. The sensors can only be accurate to a couple of degrees. In cold weather my truck runs 186 to 190 coolant temp and 6 - 8 degrees hotter for oil in steady state unloaded highway driving around 65 mph. You can always see the coolant temp move far more quickly than oil temp. The coolant sensor is right beside the thermostat so it seems to react quickly once the thermostat opens and coolant flow increases to the radiator. Oil temp seems to vary with about a two to three minute lag. Try running hard up a long hill in the summertime towing 8K lbs in 100 degree heat, then coasting down the other side. You'll see 220 degrees on both, then the coolant goes down to 190 quickly because you are off the power and the fan is on high speed, and hey presto, you have a 25 - 30 degree delta. Three minutes later it's back to normal.

Your truck sounds completely normal to me, fwiw. You say you see 10 degrees difference with the coolant bopped down to 186 for a few minutes, what is the oil temp when the coolant is steady at 190, and you have been driving on the highway for 20 minutes?

Edit: I like it when I get questions that let me learn something. Here is a typical automotive sensor: http://www.ge-mcs.com/download/tempe...20-542A-LR.pdf
Accuracy at 25C (around 80 F, and a standard temp for certification) is 4.87%, and at 0C (freezing) it's 6.33%. That is for a brand new sensor, and presumably ours are around 8 or 9 years old now and they do get worse with age, so it you had one sensor trending high, and one trending low, at freezing temps you could easily see a 10% - 15% difference in the sensor's outputs. That has to then be multiplied by the accuracy of the sensor input chip in the computer, which might itself be 1% or 2%. But - the accuracy might not be perfect for absolute measurements but it will be quite accurate for repeatable measurements, which means 190 degrees today will probably be quite close to 190 degrees tomorrow or next week. Plus they get more accurate at operating temps of around 80 - 90 C (190 - 210 F)

Brian

 

For what its worth I believe the highest oil temp I have seen since I started monitoring has been about 203 degrees. At this oil temp tends to be 6-8 degrees. It is more in the mid 190s for EOT that I see the higher deltas.

 

Just got my sg2 hooked up and I was showing EOT of about 180-190 and the water temp never went above 182. This was driving normal on the highway at 65 for an hour.Was wondering if this was an indication I need a new thermostat
Or if this is in the normal range of things.

 

That depends on the OAT too. At 20-30 degrees outdoors, the cold air rushing across the radiator will keep it on the cool side. Try blocking off some of the airflow and 'Voila' ! You'll be right up to 190+. Mine will run between 183-188 on cold days so I wouldn't sweat it.

 

If you consider that the temp that the thermostat is "supposed" to start to open is 190, then 182 is low. Not sure I would change the thermostat for that difference, but it is low, meaning that it is opening too soon or not closing all the way. Since it is opening too soon and allowing coolant to flow into the radiator, the trick of blocking the radiator will probably help, but it won't fix the actual problem. The question is - how much of a problem is it? I don't know the answer to that one! FWIW, I changed my thermostat in the fall, when it was letting the engine run at 165 - 170 maximum, and now I see 186 - 188 with a brand new thermostat. It gets up higher with a load, obviously, but that is cruising around.

Brian

 

Ok thanks I will keep an eye on it.

 

Is your Oil temp getting close to 190? or is too cool as well?

 

When I got off the highway I had
191 EOT
181 FWT
149 TFT
The EOT And WT stayed close to the same until 182 then the oil went slowly to 191 at its highest point and the WT stayed at 182. It's in the low twentys today.