Ahsai?s oil temp gauge revisited

Some members here may remember Ahsai�s incredible thread where he tapped into the oil temp sensor pin in the DME and created a circuit to drive a VDO oil temp gauge. Here is that thread for reference: https://rennlist.com/forums/showthre...errerid=188196 I was very impressed with his work and decided I would give it a shot and build one for my car. I did take some liberties with his design and develop it a bit further. Since I would be using the VDO vision gauge, I simplified the circuit and eliminated the switch, LED, and trim pot, since they are not needed when using the VDO gauge. I tried to make the circuit on a breadboard and soon discovered my soldering skills were not up to the task. So I went ahead and created a gerber file and sent it off to get a pcb made. I also added connectors for the input and output, and incorporated the heat sink into the surface of the pcb. The result came back great and simplified the soldering enough so I was confident in the task. Here is a pic of the bare board: Then programed the ATTiny with Ahsai�s code and populated the pcb with the components. I decided to sacrifice my cubby and mount the gauge in a single DIN gauge pod I found on eBay. PREMIUM Universal DIN Gauge Pod - 52mm (2-1/16") single pod radio mount https://rover.ebay.com/rover/0/0/0?m...2F262604293825 The mounting ring that came with the gauge is slightly taller than the DIN slot, so I had to sand it down, and I JB Welded standoffs to the back to mount the pcb. Next I used a trim piece from the AC controls, modified to fit the mount from eBay, Here�s a pic of the finished assembly from the back. And wired up before installation. Power came from the unused phone connector that is tucked up into the center stack. The gauge light is wired into the circuit that runs to the ashtray light. The scariest part of this mod was tapping into the DME connector that contains the sensor wire. 88 wires come together here, I needed to find #73!, and I ran the wire up under the console to just above the AC controls. And fully wired in from from the back: Mounted in the center stack: And best of all, it works !

Awesome job!

Wow, great job! I love the pcb and the install. Thanks for taking it this far to show the possibility!

Good job !!

Awesome work! Have a friend looking to do this in his 996 with a VDO gauge as well. You've gone next level with a PCB!

Super job....unfortunately not everyone has that ability.....

Very impressive. Love it.

That's very cool. It would be awesome if somehow we get rid of the speedo in the dash and just use the digital speedo (that's all I use anyways) and move the oil pressure gauge next to the oil temperature so you can actually read it!

Very nice.

That is outstanding! How long (knowing what you now know) would this take?

How did you route the wire? It goes all the way from the back right?

@808Bill assuming you have all needed parts, I’d say it’s an easy weekend project. Actually assembling the circuit board is the easy part. I could do it in an hour. Mounting the gauge and pcb to the DIN pod is also quick, but the JB Weld used to mount the standoffs needs several hours to harden, overnight for full cure. I needed to make some minor modifications to the DIN slot above the AC controls and to the trim ring around the pod. This took a couple of hours, but I took my time so it looked as good as possible. Wiring the assembly to the car took me 3 hours to access the DME, splice in the wires, and run them out of sight under carpeting, console, etc. Could it be done quicker? Sure, but this is a hobby car for me, and I like to take my time and enjoy the process. @turbogrill there are a total of 8 wires. 3 just go from the pcb to the gauge, Literally a few inches and is done on the workbench. 2 wires (12v power and ground) to the pcb came from the unused phone connection right below the AC controls. 2 additional wires connect to the gauge lighting, I spliced into the light in the ashtray behind the window switches in the console. Only 1wire goes from the DME to the pcb. The. DME is located under the parcel shelf behind the passenger side back seat. I ran it under the carpet in the rear and under the console and forward to where I mounted the gauge. All wiring is in the car interior, nothing in the engine compartment or frunk.

Very cool! I don't think it would take much to make a board small enough to attach it to the back of the gauge (or maybe even mount it vertically next to the gauge as-is to make room for an additional gauge or two.

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Nice! When the 996 was a track car my plan was to do something similar but with a Circuit Express ( https://www.adafruit.com/product/3000 ). You don't have time to look at a gauge when racing, has to be lights. But I don't track the car anymore so don't see the point.

Coopduc, have you tried a steep uphill run in low gears for 10-15s? You should see the gauge respond very quickly.

Ahsai- I’ll have to give that a try. The last pic in my original post shows the gauge a tad over 200deg after a relatively easy flat 10 mile drive.

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Yes, I�m confident it could be done, esp. if using surface mount devices instead of through hole components. Soldering those small devices is definitely beyond my current capability, however. There could be room for 2 additional gauges...which ones would you propose?

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Boost and EGT gauges. It could also make room to flush mount a radar detector in the extra space.

cool. Would it be better (and sleeker) to put a digital LED matrix type display that just shows the temp (maybe changes light color from green/yellow/red if a certain value is reached?). The VDO gauge is cool but a discreet display would be nice. Wish there was a way to simply tap into the digital clock LCD in the instrument cluster and have it just output the temperature instead of the clock

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Or, how about using it to drive the original oil temp guage already in the dash! Oh wait, I'm an idiot, that is the water temp!!! Sorry... The OP does very impressive and tidy work. Well done!

Great work - Does the feed need to come from the DME or can it come directly from the sensor/sender? Or is it not worth running the cable all that way?

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I did a digital oil temp gauge setup on mine using the input from the factory oil temp sensor, but it doesn't change colors. Uses an Arduino for conversion. You Tube

Sorry to revive this thread, but how much does it run to get a PCB made like that? VERY impressive, I'd be willing to bet you could sell those (obviously not a high volume...)

Looks like we have another product opportunity! There is a market for this. Hint, Hint...

If OP wants to commercialize, send me the BOM, Gerber, Fab data and how many you want and I’ll let you know what the MFG costs. I happen to have a couple of these. ETA - I see it’s all PTH - got a couple of these too

I have been working on an updated version of this that uses a wired RS485 network to measure distributed sensors that could be fitted anywhere and displays data on a small LCD up front, with a bluetooth serial output facility to tie it into TrackAddict for datalogging. Because I have been so busy with work and random other problems it's not complete; I will probably finish it over the winter. I have been running the prototype in my car this year measuring oil temp and ATF temp. Also the complete unavailability of the STM32 microcontrollers it's based on has been a problem, too.

Innovation at its best guys!

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Not sure if you’re referring to the original design using the VDO gauge, or porschetech3’s design using the digital display. Anyway, I had the original unpopulated pcb made by pcbway.com, just sent them the gerber file, very inexpensive, if I recall the shipping was more than the boards. They can provide an online quote using their website. Purchased and soldered the components, etc. myself, but now I think pcbway will do the assembly also. I have a couple of spare bare boards, if you’d like to try to put one together.

I may be able to help you on the component availability Aaron if you need. Just give me a shout if you want.

I would be in for 4 units if we can arrange a group purchase Mark

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Hello there Coopduc, Amazing work, I am in the process of making something similar in Europe for my 996. May I kindly ask for the schematics, I am also planning to use a VDO gauge and I am not so skilled with modifying electronic circuits, I am planning similar changes as you have done to Ahsais diagram. Thanks!

This should help

Is it possible to connect the oil temp sensor to the outside air temp sensor and display on the OBC? I have a parts car that on a 50 degree day the outside temp was showing over 100. I have not looked into why but this thread just maybe me go hmmm. there is also a switch by the fuse box to turn on the fans.

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Very clever idea, IF both sensors happen to be the same resistance, then just would a matter of a jumper harness..

if someone makes one so it can replace the digital speedo (and the color is matching) I will pay well for it.

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I don�t know my ohms from my volts, I�m just the idea guy.

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Wow many thanks! Sorry for the late reply, I was preparing for a track day today :-)

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Hi there Coopduc! We have started working on the dev. board, thanks again for the input. We are combining Ahsai's and your posts to make our own. Hopefully you could help out one last time promise :-). So Ahsai was using an AMP buffer (U4 in his schematic, image below) (L272M), in your model I do not see it used, do you limit current draw from DME? If so, how? We couldn't find a L272M as it has been discontinued, so we are using a LM358P. Thanks a heap! Regards from Slovakia

Hi Vect, i am also using it in similar way. See below. Also, L272m op amps are still available on eBay. https://www.ebay.com/itm/392649040506

I'm interested in this, but I'm also exploring more factory looking options. I don't really want an aftermarket gauge. After a while looking at wiring diagrams, there may be some options, but which create questions that others may know. I actually have a spare used Mk2 instrument cluster on order to mess with. Options that would only require changes to external wiring at the cluster harness: 1) The cluster voltage guage is read from a wire that comes straight off of the alternator. The cluster is powered separately off of switched power. Reading oil temp sensor voltage and outputting scaled voltages in place of the alternator voltage might be possible. I'm not sure what low voltage/battery alarms might be triggered though. I need to test this. 2) The external air temp sensor is wired straight into the cluster and nowhere else. Inserting a circuit that translates oil temp voltage to 'external air temp' readings might be possible, but I need to explore the range of air sensor values. It might work to convert the oil temp to Celcius, but to display in Fahrenheit. i.e cluster displays 100F, but that actually means 100C, or 212F. If the gauge goes to 125F display, that would capture an actual oil temp of up to 257F. **Does the external air temp get used anywhere else? It would have to be transmitted out of the cluster over Canbus. Is it used for the HVAC system or radiator fans? 3) The fuel level gauge also goes straight into the cluster. Replacing fuel level with oil temp would be a great location. But then the voltage gauge would need reworked into a fuel gauge, and that's multiplying the challenge. Opening the cluster: 1) An arduino can directly drive the gauge stepper motors, and I've found posts of one person doing this (for a home driving simulator), but with no details. So, it would be possible to keep the harness inputs as is, but with some major internal mods. The cluster computer would not know a difference, but I would drive the Battery Voltage gauge stepper motors from an external Arduino reading the Oil Temp voltage. Any thoughts? I work very slow, but I hope to figure something out in time. Last, if any of these work, does anyone know a place to get custom high quality gauge faces made?

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Would love to see this happen (oil temp in place of volts) just like the Carrera GT! Something plug-and-play with a gauge overlay to replace the volts overlay I think would be a winner.

This may have been covered previously but Martin Hill has done some need mods to the gauge cluster for oil temp You Tube

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Thanks. I saw that. But unfortunately, as far as I've found, he doesn't show anything about how he did it, and certainly nothing reproducible. So the rest of us are left starting from scratch. If I missed the explanation though, please point me in the right direction!! EDIT1: He does say this in the comments, but it's minimally helpful until I dig into it myself. EDIT2: This guy has the most detail on a 997 cluster. The linked video is the first of an 8 part series he did to integrate the entire cluster with a racing sim. The production quality is low, but he gives some details. You Tube

Anybody made any progress on developing a product thats available on the market for us non-electrical engineers?

Found this while looking for a way to put an oil temp gauge on my targa. I didn't think it would be so complicated! There's no place on the engine to pull out a plug, screw in a sensor, and then run some wires? Also I'm looking for an analog gauge. Not racecar so I don't need quick-to-read. I just want to be able to glance at a needle and see if it is pointing in the direction that lets me tramp on the loud pedal. For location I was thinking of one of these from Autometer. https://www.autometer.com/2-1-16-sin...911-99-01.html

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I'm pretty sure that there are other threads on here with adding an aftermarket oil temperature gauge. I actually think there is a symmetric port on the side opposite the oil pressure sender (the heads are symmetric) that maybe some people use, but that vague memory is the extent of what I know. This thread was specifically about pulling the data from the built in sensor and the ECU. Further, I am still interested in using the built-in ECU data, and using one of the built-in gauges. I really don't want to add an aftermarket gauge. I actually have a second 996.2 cluster that I bought sitting on my workbench to mess with, but haven't had much time to work on it. If you don't mind aftermarket sensors and gauges, there are much easier solutions.

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I just ordered the dual gauge pod. Glad to see that Auto-meter is supporting the 996/986 ... But it does say due to demand and Covid, may take a while to ship...lol

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Skip, what gauges are you going to run and how are you going to connect them?

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That's pretty slick. I have VDO gauges in the e30 which look similar to the Porsche gauges. Here's oil temp next to the Porsche cluster. It looks like the red on the needle is a tad off but the oil can and thermometer look like an exact match.

It is best to measure oil temp somewhere where oil is flowing. Measuring at the end of a pipe is not very useful. The best way is to stick the oil temp probe into the oil flow as soon after the oil cooler as possible. That is tough on the M96.

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Since I have a "manual" oil pressure gauge taped to the "outside " of the windshield for test purposes of the UIDS, when I remove that finally, I will put an aftermarket high quality electrical oil pressure gauge in the dual pod, since the factory gauge sucks so bad... Then in the other gauge Pod I will put a "wide band 02 sensor " to accurately monitor AFR , since our 996's only come with "narrow band 02 sensors".... I love gauges to monitor what's happening in real time, I use my big screen phone connected to the OBDLink MX+ dongle with all the PIDs set to gauges I can scroll through to monitor all PIDs available.from the OBD channel. (Running a Custom Torque Pro Dashboard) Right now I use a generic phone mount to display the additional gauges, but when Yaz gets the "custom phone mounts" that mount to the hazard switch, that's what I will use... I have talked with AIM about doing something Custom specifically for the 996, but so many variables and ways to do it, decisions to be made, I don't have the time to devote to that right now with the UAOS and UIDS I'm getting snowed under...I had to hire another part time helper and train them...

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The UIDS has an oil temp port built into the side of it specifically for the oil temp. The temp of the oil in the sump will represent the "highest temp" that the oil has reached.. Measuring the oil Temp after the cooler will measure a different delta, Of course the data at both places would be helpfull, but my opinion is I want to see the "highest" the oil has gotten..

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Skip, is there a specific OBDlink MX + that works for the 996?

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Apologies for the sidetrack. My BMW Z4MC has oil temperature in the gauge cluster, but not water temperature. I'm comfortable with that arrangement. I'd be good with having the current water temp gauge show me oil temp instead. Perhaps even switch between the two?

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This is another reason why I'm excited for mine..

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Does the torque pro app have a PID that shows oil temperature?

Oil temp is not an SAE OBD2 PID, it's a Porsche special, so OBD2 readers can't display it.

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How about oil pressure?

The iCarSoft POR v1.0 reads the oil temp and Tip fluid temp real time.

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Hey, any chance you could take a picture of that in action? Would love to see both temps. Thanks.

So wait a second... The OBDLink MX cannot run oil temps thru the DME but Carsoft can? Any idea why or how? Is the carsoft tool small enough to Velcro it to something or use in a phone holder and suction cup it to the dash?

Oil pressure signal is only sent to the dash gauge. Oil temp signal is only sent to DME, and DME only sends the Oil temp signal out through the Porsche specific protocol channel, ( does not send oil temp info out on the OBDII protocol channel)

my foxwell nt-510 elite can also display oil temperature live when plugged into obd2

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Yes, but the Foxwell, I-CarSoft, Durametric, Autel, Snap-on , PIWIS ....(higher end) uses the Porsche specific protocol channel ( on the same wires as OBDII) All other scanners use the Generic Federally Mandated ODBII protocol channel ( on the same wires as the Porsche Specific protocol channel) The scanners"query" the DME with the protocol, and the DME either sends back the OBDII Mandated data-stream info or the Porsche Specific data-stream info ( depending on the Protocol ) ..

My Cobb Accessport can also read oil temp - it's just not convenient to use in most situations because it only shows on the Cobb screen or in the Cobb's internal datalog. Again, as @Porschetech3 mentioned above this is because the Cobb's reading the Porsche proprietary communication protocol.

I just saw this ad for an 06 Cayman S that has an interesting sounding setup. He thought it might only be applicable to the 9X7 platform though.

Yea, the 997/987 sends oil temp data on the OBDII protocol, but not the 996/986... Thats an interesting set-up though. I like the idea of using an Android head unit to display Torque Pro. If only he can do a few additions for the 996/986 into his controller....sounds like he has the "computer background " to do it....

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Correct. The DME is bolted to the back firewall on the driver's side in the trunk. I routed the single wire from the DME, through an existing hole in the firewall, under the foam in the roof bay, under the carpet behind the seats, and then through the center console beside the parking brake and shifter. The instructions were excellent and I was able to find the correct wire to splice immediately. What takes a while is opening up things carefully so as not to break 20-year-old crumbly plastic tabs. The wiring itself takes 5 minutes. All told, the entire project took less than 30 minutes - most of that was carefully taking the center console apart and getting behind the radio.