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I wanted to know how hot the oil in my 996 was running. A standard engine code reader can read out coolant temperature, but not oil temperature. A Durametric reader can read both temperatures and a lot of other info that a standard reader can't, so I got one.
The first graph below shows oil and coolant temperature from a cold start. Initially the coolant heated up faster, which surprised me. Now it makes sense that Porsche added an oil-to-coolant heat exchanger (mounted atop the engine): the warmer coolant helps warm the oil faster. After about 5 minutes of driving, the thermostat had opened and the coolant temperature has leveled off at 75 deg C. After about 7 minutes of driving, the oil has warmed up to the coolant temperature and continued heating until it levels off at about 86 deg C.
I stopped to fill the gas tank. By that time, the coolant and oil were at about the same temperature. After a few minutes of driving, the coolant cooled off a bit to 80 deg C and the oil warmed up and leveled off at 91 deg C. At this time the oil-to-coolant heat exchanger is still working, but in the opposite direction, cooling the oil with the cooler coolant.
Reading these from OBDII will give some level of "calculated value". I only trust data thats gathered via the CAN, and I have seen huge deviations from CAN to OBDII when measured simultaneously.
The "heat exchanger is exactly that, BUT the factory was more concerned with heating the oil up faster, than they were with cooling it down? Why? due to emissions compliance.
Jake, in another thread you said that you inserted your own temperature sensors in various places in the engine. How did these measurements vary from what the OBDII output reads? Were there hotter and less hot points within the engine?
Absolutely... Early on I learbed not to trust OBDII for development. A stand alone data logger that can use OBD inputs as well as stand alone inputs, taught me a lot. Comparing those to the CAN data proved that the factory wanted us to see some things, and not see others.
Sensor placement also makes a huge difference, remember, the ECU needs certain temps at certain times, so there are times when sensors are placed according to what the ECU may want for emissions or etc. The coolant trmp sensor is placed in an awkward place, that makes no sense to me.
Also, I haven ever been able to prove that oil trmp is more than a calculated value from the CLT. The oil temp sensoris supposedly integrated with the oil level sensor unit. I have yet to be able to gather this data directly from that unit.
I only use my own sensors, placed where I want them. What the factory wanted me to see, is not what I want to see.
The stock oil level/temp sensor is a DUAL sensor, extending to the bottom of the oil sump. Part of it is measuring the oil level and the other part is just a simple NTC resistive temp sensor, which feeds the DME. It's also what the Durametric reads/shows, definitely not computed from CLT.
With this setup, you can see the oil temp goes up INSTANTANEOUSLY when you push the car (e.g., going up a grade at WOT) when the coolant temp stays the same.
Um...I was never able to retrieve any OBDII data on oil temp. I only used Durametric to retrieve the oil temp as a reference. However, I did find a source of that sensor and was able to confirm it's just a simple NTC sensor with the resistance vs temp curve well defined.
Come to think about it what you tried and saw may make sense because the DME is able to detect the sensor has been disconnected so it just uses (and reports) substituted vales (e.g,. to control variocam). Same thing for the MAF sensor. However, I guess if the sensor is plugged in, the DME should use and report the measured value though.
MICHAGOITMTAIIF
(My instrument cluster has a gage on it that measures temperature and it's in fahrenheit).
The US cars have the coolant temperature gauge in degrees Fahrenheit. Same with my OBDII reader. The Durametric, however, reports temperature in degrees Celsius, so I used that for my graphs.
Were you driving in normal speed local roads for this graph, stop and go traffic, or highway? I'm trying to figure out what water temperature makes sense to start really pushing the car. Some people believe that the car can be pushed before the water temps are stable. Same idea applies to oil temps, but I've always waited until I believe both oil and water are pretty much at operating temps, which is about 20-mins. However, 20-mins might be too conservative.
Also, how long does it take the valves, pistons, combustion chamber, connecting rods, and other high temperature components to be at the right optimum temperature after the engine has been restarted where it was previously running at operating temperature? E.g., You drive the car for an hour, stop for gas or pull over, shut the car off and it sits for 5-15 mins. I wouldn't just get in the car and use full throttle and RPMs on the basis that it still takes a minute or two for the hot components to get back up to operating temps, even if the coolant and oil are still near 180F.
Were you driving in normal speed local roads for this graph, stop and go traffic, or highway? I'm trying to figure out what water temperature makes sense to start really pushing the car. Some people believe that the car can be pushed before the water temps are stable. Same idea applies to oil temps, but I've always waited until I believe both oil and water are pretty much at operating temps, which is about 20-mins. However, 20-mins might be too conservative.
Also, how long does it take the valves, pistons, combustion chamber, connecting rods, and other high temperature components to be at the right optimum temperature after the engine has been restarted where it was previously running at operating temperature? E.g., You drive the car for an hour, stop for gas or pull over, shut the car off and it sits for 5-15 mins. I wouldn't just get in the car and use full throttle and RPMs on the basis that it still takes a minute or two for the hot components to get back up to operating temps, even if the coolant and oil are still near 180F.
Thoughts?
I was on surface streets for the first few minutes, then on the freeway. The gas station was two blocks off the freeway.
From the coolant and oil temperature data, the oil temperature lags the coolant in getting up to full operating temperature. I'd say that oil is at operating temperature 0.5 to 1 minute after the coolant temperature stabilizes. I usually wait for what I think is a stable oil temperature before revving it up above 4000 rpm.
After the coolant and oil are warmed up, other parts still get hotter. I can tell a big difference if the car has been run for 5 minutes vs. 30 minutes in the heat radiating from the engine compartment.
I don't know the difference among the valves, pistons, and other parts. Jake Raby might have some data. He has reported using something like 12 temperature sensors in different parts of the engine.
If you have it warmed up, then park for 5-60 minutes, it will warm up much faster than from cold, as I'm sure you've seen from your temperature gauge.
I was on surface streets for the first few minutes, then on the freeway. The gas station was two blocks off the freeway.
From the coolant and oil temperature data, the oil temperature lags the coolant in getting up to full operating temperature. I'd say that oil is at operating temperature 0.5 to 1 minute after the coolant temperature stabilizes. I usually wait for what I think is a stable oil temperature before revving it up above 4000 rpm.
After the coolant and oil are warmed up, other parts still get hotter. I can tell a big difference if the car has been run for 5 minutes vs. 30 minutes in the heat radiating from the engine compartment.
I don't know the difference among the valves, pistons, and other parts. Jake Raby might have some data. He has reported using something like 12 temperature sensors in different parts of the engine.
If you have it warmed up, then park for 5-60 minutes, it will warm up much faster than from cold, as I'm sure you've seen from your temperature gauge.
Yeah, I was surprised that oil doesn't lag water, but as someone pointed out, emissions need to be met.
Ive seen people warm up their engines for only a couple mins and then lay the hammer down. Temps are still 100F in some cases. And I've seen people lay the hammer down after only seconds of a warm start. Seems like a bad idea to do the latter, but not so sure about for former.
Yeah, I was surprised that oil doesn't lag water, but as someone pointed out, emissions need to be met.
Ive seen people warm up their engines for only a couple mins and then lay the hammer down. Temps are still 100F in some cases. And I've seen people lay the hammer down after only seconds of a warm start. Seems like a bad idea to do the latter, but not so sure about for former.
I've warmed up cars, and I've taken cars from zero to redline on start up in 10* weather. While I personally believe in warming things up, I haven't had any negative affects of not warming up.
07-12-2015, 04:16 PM
Measured 996 oil and coolant temperatures
