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YOUR RESEARCHMeasured 996 oil and coolant temperatures
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Disconnect so it just
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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,.
Leading evidence: 'Disconnect so it just' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Disconnect so it just' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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I only used Durametric to retrieve the oil temp as a reference.
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Suggestion
So why are people so reluctant to replace the heat exchanger with a small fan+oil cooler ?
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Suggestion · Original poster
I can tell a big difference if the car has been run for 5 minutes vs.
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Disconnect so it just
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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,.
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Suggestion
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,.
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Suggestion
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.
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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.
I've made a circuit to read the voltage directly on that NTC sensor and show it on a VDO oil temp gauge
https://rennlist.com/forums/996-foru...mp-sensor.html
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.
I've never been able to gather that data into a logger...
BUT disconnect that sensor from the harness while driving and the OBDII data continues to change... Try it.
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.
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.
DrMEMS,
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.
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.
Jake said: "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. "
So why are people so reluctant to replace the heat exchanger with a small fan+oil cooler ? Yes, I know that space is a problem but there must be a few practical solutions ?
The HeatX is not a Smog device that is checked at Smog Test time. Maybe it would generate a code related to slow engine warm up in cold climates ?
The other advantage of the LN Heat exchanger delete plate is that you get a perfect(?) port for a 'real' coolant temperature sensor to control a real gauge.
http://lnengineering.com/oil-cooler-...-m97-only.html
http://www.planet-9.com/gallery/file...pass_plate.jpg
http://www.planet-9.com/gallery/file...eletefront.jpg
To LN's credit they promote the oil cooler product in the context of extreme use. They are not saying it is essential for DD.
For that reason I recently asked about the merits of this product/project in a Boxster Racing Forum. One of the very highly regarded experts said he did not consider it necessary .
It is a moot point if there is nowhere sensible to put the oil cooler+fan anyway !But I still like Flaps' idea of incorporating it into the spoiler :-). Very creative.
270 degrees F for oil is not sooo bad perhaps? But to obtain a reading of 270 at the oil temperature sender, the oil had to be wayyyy above that somewhere else? So the question is - does the LN oil cooler do much to reduce those extreme and very localized temperature spikes ?
What was the outside ambient temperature during your data collection? Was it raining by chance? [I've found that rain/wet streets have a strong influence on lower oil temps.]
