Tracking oil temp

Was wondering if anyone has had any success in tracking oil temp in a 996 on a regular basis. I have been looking around for details on how I would accomplish this, but have not found anything that sounds like a permanent solution. I have started tracking my car, and with living in Texas, heat has become a worry of mine. Want to at least track the oil temp to help keep my car healthy. I have heard of two options: - Connect using durametric on a laptop. The value can be pulled, but having a laptop connected and open at all times seems to be a hassle. Possibly mounting a tablet running windows could make this a bit more feasible? - I have heard the oil level gauge also measures temperature. I have not been able to find which wires I would want to tap into, and whether I would want to tap in by the sensor, or off the computer. Would rather not cut into wires if possible (extension?), but am open to the best option. Anyone come up with a successful solution?

The oil temp is a calculated value not a true value. You will need to add an oil temp sensor into the sump to get a true reading. You are spot on about its importance in our part of the world though.

Actually our oil temp is measured directly by the oil level/temp combined sensor. The sensor is very responsive because it measures the hot oil that comes from the main bearings when it drains back to the sump. You can tap the sensor signal but it will be quite involved https://rennlist.com/forums/996-foru...mp-sensor.html

Either read from the CAN, or install a stand alone gauge and sensor... The OBDII value is calculated and cannot be trusted.

Jake, Do you happen to know of any way to read the can bus without a program running on a laptop? Ahsai, Has that worked out for you long term? You mentioned using durametric to get the signal and output it, does that mean you have to have a computer connected at all times for the gauge to work, or did you use it just to tune the signal for the arduino to pull the data directly from the DME?

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It works well but I never installed it permanantly. Once the concept was proven, I moved on. It's the latter. Durametric uses that sensor so I measured the sensor output voltage and the corresponding Durametric reading. Then I implemented that volt to temp mapping in auduino. The auduino is also used to power the VDO gauge to show the correct reading. It's a stand alone unit. The circuit and the vdo gauge power up the instant you turn the key. No computer is required. The best part is it's so responsive when you mesh the gas to go up a slope, you can see the engine oil temp goes up instantly while the coolant gauge doesn't move at all.

Appreciate the response! Just finished reading through your thread on how you implemented the solution. I really like how you were able to tap into the DME without any permanent modifications/splicing of wires. Hopefully someone else has been able to implement a simple solution to tracking the temp, but your way sounds like it could be fun to play with.

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Thanks! You can always wire a stand alone oil temp sensor in the sump (somehow) but where's the fun in that?

afx, I'm in Austin, as well, and ended up putting a Mantis sump and a 3rd radiator on my car. I don't have a means of tracking oil temp, but my pressure is good after a session at COTA, and my coolant temps are pretty solid as well. -Jon

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Did you notice any improvements in oil/coolant temps from before and after the 3rd radiator and sump? I have been thinking about doing the 3rd radiator was well. COTA sounds like it would be a ton of fun, I plan to get out there someday! I have been going to Harris Hill Road in San Marcos and noticed when I went out last weekend my coolant temp started going above the normal level (usually right between the 8 & 0 in 180, but was a little past the 0). Had not really noticed this before at the track, but this was also 100 degrees out at the time. Also noticed the oil pressure at idle a good bit lower after the runs. I might just go ahead and do sump & radiator just in case, but was hoping to get some baseline numbers in with tracking oil temp first.

I took a pretty systematic approach to solving my issues. I started out with the x51 oil pan, but saw the oil pressure drop after 20 minute sessions (both on track and at idle). This was with 5w40 in "cooler" weather. I bumped up to 5w50 oil, which eliminated the pressure drop due to heat, but I was still seeing a slight rise in coolant temps (similar to yours as it was past the '0'). I then added the center radiator, which eliminated coolant temp rise. Finally, I was seeing pretty significant pressure drops through turns 16-18 at COTA (2 bar or slightly lower at 4k rpm). After installing the Mantis sump, there are no drops in pressure. It's not as accurate as getting actual temps, but given that I don't see a significant drop in pressure at idle, or at speed, I'm pretty confident that things are running smoothly. For reference, I'm running a GT3 suspension and street tires. I have some more time at COTA, but I think I'm relatively fast out there. I hope to get down to Harris Hill more frequently, this fall.

Hi all, oil temps are too high. On the mantis race cayman we use 2 oil coolers each mounted at the front of the car, each fed by a 3" hose. We use a tilton oil pump and tap to holes in the Mantis sump, and circulate oil to the coolers, 195 degrees oil temp in the sump, normally you have about 230'240 oil temps without additional coolers. I realize that on street cars this set up is over the top. I suggest that you can purchase a oil cooler with a fan attached, theres room for that in all porsches. lots room in the "tunnel" to mount the oil pump. Mount oil cooler besides the trans. Hope this helps. It can be done.

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I e done this type of circulating system as well. The Tilton gear oil pump works well with our hand built oil cooler fitted to the factory 3rd radiator position. What I prefer is my high volume main oil pump, coupled to this same cooler, as it cools the charge oil before its delivered to the bearings. With my dry sump system with remote reservoir we sometimes use two coolers, one to cool charge oil, and one to cool bypass oil before it returns to the reservoir. All in all, the oil runs too hot in stock form- period.

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Nice to see that you were able to notice the individual parts make a difference in the issues you are seeing. I have the parts for the 3rd radiator and am thinking about getting an X51 oil pan. If you see a gray 996 convertible at HHR, stop by and say hi, would be nice to check out your car.

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For street cars adding an oil cooler, what would you suggest for plumbing it in? I am guessing you are running a pretty deep sump to be able to tap in, which might be to much for a street car? I have seen a couple oil cooler deletes which allow adding an oil cooler which might be an easy route to take.

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I took some of your ideas ( thanks!) and did a little more digging... on the fence currently about wether or not to sell a packaged unit that displays a few values such as oil/coolant temp and oil pressure (digital not analog). The electronics side is easy but I need to work on the display/wiring/mounting solutions that are OEM quality. At the very least I'll build something permanent for myself since my car was purchased mainly as a track car. In the process I did find that my oil temp sensor resistance was out of spec vs. a new one. I wonder if others have the same problem and don't know about it, as we never see oil temp.

William - just an idea, but I heard there there some OBD2-Bluetooth dongle in the wild that can display those values and maybe even send them to a Car stereo as an app which run on Android ...or maybe I'm just dreaming

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Hi William, I open sourced the info so anyone can build one if they like. Hope to see you can come up with a kit 'cause I'm sure a lot of folks will be interested. Just wondering how did you know your sensor is out of spec? Did you take it out and try to calibrate it with a precision thermometer? Since you seem to have the motivation and skills, I would write down here what I've found so you have a better starting point. - You can only get the oil temp from the built-in sensor two ways: 1) By tapping the voltage of the sensor then make your own circuit like I did 2) By query the DME for the actual interpreted temperature To achieve 2), you have to connect to the K-line and init the communication and query the DME like Durametric (or other Porsche scan tools) does. Basically reverse engineer Durametric. If it can be done without a computer, that would be the holy grail! Don't waste your time on OBDII (bluetooh or not), the oil sensor PID is not exposed to OBDII.

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True, I had durametric reading in mind, which obviously is proprietary

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I've edited my posts. The oil temp sensor is actually on the same K-line as the OBDII K-line but the protocol to retrieve it is different than the regular OBII protocol.

What about pre-2002 cars like mine, no can-bus here IFIRC

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I don't know who started mentioning CAN-BUS for oil temp sensor but it's wrong info. CAN-BUS uses a twist-pair physical wires and K-line uses a single wire. Totally different physical layer. Our car uses CAN Bus but it's for tiptronic and PSM, etc. modules. If you look at the wiring diagram, it's very clear regardless of MkI or MkII. The OBDII port pin 7 (K-line #1) connects directly to the Alarm Unit, which then connects to the DME directly via the "W Lead". You don't talk to the DME directly (probably a security feature). The other K-line is on pin 3 of the diagnostic port, which connects to multiple modules such as ABS/tiptronic/airbag. That's the pin Durametric interfaces with to clear the ABS/airbag lights. A generic OBDII scanner will only connect to pin 7 so that's one of the reasons why it will never be able to reset your airbag light.

Has anyone tracked the difference between the calculated and actual oil temp values? Is the calculated +/- a few degrees of the actual or is it a much larger delta than this?

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The oil temp displayed by Durametric is not a calculated value on the 996. It's a true value measured by the oil temp sensor in contact with the engine oil. The sensor is combined with the oil level sensor and it's in the middle of the engine behind the a/c compressor. The word "calculated" means it's derived. For example, in the Torque App, it displays the intake manifold vacuum, which is calculated because our engine doesn't have a MAP sensor.

So is the value displayed in Torque or Harry's Lap Timer through the Bluetooth ODB II dongle the actual oil temp?

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Again, you can't get oil temp sensor reading from a generic OBDII bluetooth dongle. Torque does not display oil temp for our car. I don't know about Harry's Lap Timer but if it does display oil temp, it cant be read by the OBDII bluetooth dongle.

Ok, I hadn't verified they did with my car, only that they did general. Thx Ahsai.

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Not sure how I missed your reply for so long... I did perform a bit of testing with a precise thermometer. Unfortunately I also destroyed a couple oil temp/level sensors in the process. As fun as this was I ended up not using any of this data other than to find out that my original sensor was reading low by 30+ degrees (calculated temp... resistance was reading much too high at a given temp.). I actually did also find out that my lab skills aren't worthless. Instead of the test data, my voltage to temp conversion now uses the Porsche factory equations/coefficients for the oil temp NTC thermistor (reverse engineered in a different way). Like you did, I'm currently reading voltage that the DME sees from the oil temp circuit. I tried the same VDO gauges but decided that I didn't like them that much. I'm currently working on a mount that holds a digital display and gives oil and coolant temp. I actually don't have a working oil temp sensor currently and will resume development when I get a functional one back in. BTW the DME uses coolant temp for oil temp when there is no oil temp sensor available... Jake Raby mentioned once that if you unplugged the oil level sensor the DME still returned a value for oil temp. This is the reason why. It makes sense because they should always be relatively close in value due to the oil/water exchanger.

Its supposed to run about the same, but it does;t on the track. Why? Because the factory great exchanger is thermally overloaded with high RPM. I see 60-80F differentials between coolant and oil temps, and ambient temps make a huge difference too. People that believe you have to keep the engine at redline to have fun are the other issue, as all that added RPM= oil temperature. This engine has 24 valve springs, engines post 2002 have dual springs on the intake that are of interference design. This alone adds huge oil temperature increases. The factory heat exchanger is exactly that, it isn;t designed to keep oil cool, as much as it is to heat the oil up faster, due to emissions constraints. I throw it away whenever possible, and partition the coolant cooling from the oil cooling.

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The stock sensor has a +/-5% accuracy per its spec. I also have the resistance to temp curve for the sensor published by Porsche. Once you can derive the internal resistance used inside the DME, you can get the voltage to temp curve (sounds like you did that already). Sensor value substitution is pretty common (when it makes sense). e.g., when the MAF is unplugged, Durametric still shows MAF values because the DME uses other sensors and engine data to derive that.

You believe that?

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Depends on what I find when I test it in hot oil I plan to calibratfe mine during the engine rebuild.

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This all makes sense to me. Has anyone upgraded the factory location exchanger to something that keeps oil/water within 20-30F? External air oil coolers are great, but unless I had an accusump with oil up front already, I would prefer to minimize oil lines running around the car. My car will see track time at high temps next year so I think this is something that I should be ready for.

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You won't cool 280F oil with coolant thats 220F. Its not happening... Not even with a pair of Cayenne Turbo heat exchangers. (been there, done that) Partitioning coolant and oil cooling is the only way I've been able to control oil temperatures. With that I've had my R40 engine (4.0, 430HP) to 200F in a Cayman at Road Atlanta with track temps of 135F and ambient air temps of 97F. IAT that day was reading 117F.

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I would bet that the 5% number is correct (ETA: for a new sensor)... wether or not that number is relevant based on measurement location is a different story.

I believe NOTHING that sensor tells me. Nothing.

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I'm certainly not arguing that the DME reported value is correct, but the VDO supplied NTC thermistor will do what it was designed to do. If I know the resistance of the loop, then I am certain that I also know the temp at the sensor , assuming it is functioning correctly / not broken.

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I agree because it's just an extremely simple electrical circuit. By tapping into the sensor voltage, the DME is bypassed.

Ok, you fellas can go down your own paths... Install 8 stand alone sensors in the sump (all over) with an 8 position switch feeding he same stand alone instrument...Flip between those and compare to the factory sensor.

What's the best way/location to install a sensor in the sump?

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Weld a bung onto the sump plate to be tapped for 1/8 NPT, or whatever the diameter is of the sending unit that will be used.

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I think we are mixing 3 things here: ​​​1) the inherent error of the sensor (or any sensor) 2) the location of the sensor whether it's the best location to measure and reflect the oil temp 3) DME substituting the reported value Each will need to be discussed, understood, and addressed individually.

Re 1) from the Porsche oil temp sensor tolerance curve, at the range of interest (100C to 150C), the error is about +/- 5 degrees C (or +/- 10 degrees F). Re 2), one potential issue with the stock oil sensor is it sits ~1" above the oil sump bottom, on the right side (bank 2) of the engine and OUTSIDE the plastic oil baffle of the sump. So it's perceivable with extreme g-force (e.g., hard and long right turns), it could be starved of engine oil. If that happens, I think we should see pretty sharp oil temp drop (crankcase air temp) though. This may also explain what Jake saw.

I realize this is an old thread - but from everything I was able to find, the oil temp can be accessed if the PID code can be determined - as long as the ODB software allows for custom PIDs. ODBLINK Mx wifi does allow for this - now the question is how to determine what the PID code is for temp. Any thoughts?

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From reading other threads on oil temp, it has been mentioned that the oil temp value from OBD2 is potentially a calculated value vs an actual value from CAN. Would probably need to read both and verify if they are producing the same values. As far as adding in PIDs, seems like that would be necessary, but I have no clue how you would figure out the PIDs you need.