Stock Oil Sump Temp Sensor Driven Gauge

[P_Carfahrer]

While waiting to get machine time to get my LCAs and camber plates built, I wanted to get an oil temperature gauge installed as one of my winter projects. I really didn’t want to install a sending unit on the driver side head port as many have done as I have installed the 987 airbox/MAF and there just isn’t a lot of room in that area now to get my hands/tools in there. I had looked at a thread on rennlist by Ahsai a long time ago on the possibility of using the signal from the temp/level sensor in the sump to drive a gauge.

So I decided to build and program one using some of the information Ahsai posted and tweaking it a bit. I purchased a used temp/level sensor probe and wired it into my DME in place of the one in my engine and used a NIST traceable hot oil temperature bath to heat the sensor to map out the voltage signal from the sensor to 300 F and mapped that signal to what the gauge needs to indicate the respective temperature.

I breadboarded up a driver and programmed the chip with the math function to take the signal from the sensor and then output the required signal to the gauge. The component receiving the signal from the DME tap has 500k ohm resistive value to not degrade the signal current the DME sees. I have installed the gauge/breadboard prototype and verified accurate function through Durametric. With everything now functioning I will make a PCB and a simple wire harness/box combination to install the device permanently.



Bench prototype



DME Wiretap



DME Wiring


Prototype Onboard Testing

[steved0x]

That's pretty cool, are you going to put any other gauges on there? Are you going to make a blue back light for it?

[P_Carfahrer]

Originally Posted by steved0x

That's pretty cool, are you going to put any other gauges on there? Are you going to make a blue back light for it?

Yes I have already changed out the bulb that comes with the gauge with a blue led that uses the same socket style.






As far as other gauges go, I have a 996 cluster so oil pressure and voltmeter are covered. I want to put in another gauge as only having one in the space looks a little bare to me. I am having trouble coming up with what might be useful to put next to the temp gauge. I looked at installing an Innovate dual wideband lamba gauge as I will have a tune done but am not sure if it will be particularly useful long term. I thought about installing some fan override switches like you have done but I think I will instead build another microcontroller to automatically control the fans at a lower temperature setpoint.



The biggest issue I have with the gauge install is the space for the gauge doesn't really fit. In the pictures you can see how the DIN opening bows up significantly.



How have any of you dealt with putting a gauge in this location? Have you notched out the to top rail of the opening?

[steved0x]

The spin on gauge (spin-lok?) is too big for our spot, you have to use this style:

https://www.vdo-gauges.com/accessories/instrument-mounting/stud-mount-conversion-kit-for-2-1-16-vision-and-cockpit-series-gauges.html

Somebody sells a plastic front panel that snaps in that has spots for gauges, but naturally I can't find it now.

I made mine out of a CD holder I bought from Woody and a sheet of black plastic I got from a display at O'Reilly auto parts.

A friend of mine did his, and I made him a template in Front Panel Express, and it worked out pretty good for him. Unfortunately it is lost as it was on my old laptop...

Maybe a voltmeter? Or if you are going to do some track work, some switches to control your cameras or any other gadgets you may have

[Dave80GTSi]

Yes, I second what Steve notes above - you need to use the VDO bracket, as their large plastic spin-on "nut" which comes with the gauges does not begin to fit into the space.

And yes, just buy an old CD holder and gut the drawer part. In my case I bonded it to a piece of aluminum (rather than Steve's plastic sheet), but the concept is the same.

I could not make three (3) gauges fit into the available width space, but there is room for two (2) gauges easily, with a bit of available real estate left over for a switch or two, as you may need.

Thanks - DM

[The Radium King]

transmission temp gauge. and a clock - porsches should have an analogue clock. g-force gauge. plx obd gauge.

good work on the interface - send it to fred and he can get it market ready.

[P_Carfahrer]

Originally Posted by The Radium King

transmission temp gauge. and a clock - porsches should have an analogue clock. g-force gauge. plx obd gauge.

good work on the interface - send it to fred and he can get it market ready.

Is Fred still around? I heard he has been away with a sick friend. I can send him a PM and see.

I would like a g force gauge but there isn't much information out there on a 52 mm sized gauge. The apsx gauge I could find had a video on Youtube at one time but it has been removed.

Here is a mock up of the PCB j-box with a paper PCB. I plugged it in and it doesn't seem to work.

[P_Carfahrer]

Originally Posted by Dave80GTSi

And yes, just buy an old CD holder and gut the drawer part. In my case I bonded it to a piece of aluminum (rather than Steve's plastic sheet), but the concept is the same.

That looks great Dave, did you paint that with hammered paint or wrap it with something?

[steved0x]

I would like a g-force gauge, would be cool, maybe to make a tone or series of tones, or even leds for a gsum display. Or maybe a digital min speed that would reset each corner that you coming ld peek down and see after a corner.

[Dave80GTSi]

Originally Posted by P_Carfahrer

That looks great Dave, did you paint that with hammered paint or wrap it with something?

I used nothing more exotic than a rattle can of matte black Rustoleum, standing far back away from the part so to give a textured 'spatter' droplet effect, intentionally with lots of orange peel. About 6 to 8 coat's worth.

The only (very mild) thing that I do not like about the installation is that the face of the OEM CD tray is designed to fit flush with the similar console insert below. So, by adhering the aluminum gauge plate onto the face of this tray, this gauge panel now sits proud of the (in my case) face of the stereo equalizer controls below.

Thanks - DM

[P_Carfahrer]

Pcb ready for solder work. I use an old school overhead projector to illuminate the top and bottom layers to get everything lined up and I had multiple people stop by my place and ask what I was doing with the projector. Every one of them said they hadn’t seen one since grade school.

Pcb top printed


Pcb bottom printed


Pcb etched


Pcb ready for drilling, tinning, and soldering


Pcb drilled and tinned. Yes I drilled my finger. Twice. Broke a drill bit off in it.

[MWS]

Originally Posted by P_Carfahrer

Pcb ready for solder work. I use an old school overhead projector to illuminate the top and bottom layers to get everything lined up and I had multiple people stop by my place and ask what I was doing with the projector. Every one of them said they hadn’t seen one since grade school.

Pcb top printed


Pcb bottom printed


Pcb etched


Pcb ready for drilling, tinning, and soldering


Pcb drilled and tinned. Yes I drilled my finger. Twice. Broke a drill bit off in it.

Am I a geek because I find this far too cool? I love seeing detailed work like this, and makes me wish that I had such skills (ok, I know I could, but it's probably best for the world that I didn't, lol).

BTW, sorry about your finger (and associated drill bit). Been there, done that....more than once (and you would think once would be enough...sigh).

[P_Carfahrer]

Originally Posted by MWS

Am I a geek because I find this far too cool? I love seeing detailed work like this, and makes me wish that I had such skills (ok, I know I could, but it's probably best for the world that I didn't, lol).



BTW, sorry about your finger (and associated drill bit). Been there, done that....more than once (and you would think once would be enough...sigh).

Welcome to the club. Ordering an Arduino kit with lots of sensors and projects would entertain you for a long time to get started. I got one for my 12 year old and am taking him through it because I see the huge market shortage of these skills. As a former director of engineering in a large manufacturing facility I nerd out about stuff on the car all the time building upgrades. It is an affliction. My sons tell me it seems I bought the car to work on it because since I bought it as a flood salvage two years ago it has been disassembled more than I have driven it.

The drill bit didn’t stand a chance against my finger. It was only 0.025” diameter. The multiple drillings of the finger were probably less than two minutes apart so as you see I learn slowly.

[P_Carfahrer]

After a fun evening of soldering all components are soldered and the PCB is ready for J-Box mounting. Now I need to build a harness to install it in the car.

[P_Carfahrer]

Harness and j-box wired and completed with all connectors integrated. I am pretty happy with the outcome as the install from this point is essentially plug/play other than getting the DIN plate built. I would like to find a smaller box and a plug that would be direct PCB mounted but I have not found one yet that really works.

I will install it in the next week and detail connections/routings.

[P_Carfahrer]

I installed the oil temp gauge driver a bit before Christmas but didn’t take time to post about the install.


After connecting the signal wire T to the sump oil temp sensor and to pin C5 of the DME, I ran the wire through the trunk bulkhead to the passenger side of the engine compartment.



Wire is routed under the foam drain pieces and around the toolbar, under the side vertical carpet, wire tied with ‘sticky backs’, and down the console and out the passenger side.







The grounded wire is the ground for the gauge and driver.

Driver j-Box is taped with double sided tape to top of the airbag module. Switched power is tapped from the phone preparation power wire. The power in has a 1 amp fuse.
Power for the gauge light is tapped from the center console storage light wire.



The gauge power, ground, signal, and light power wire are run up to the tray, wire tied and connected to the gauge.

I will make any future builds with a much shorter harness as it currently is too long and I have too much wire tied up as you can see.

The gauge works great using the stock sump sensor and this driver.


I have modeled a two gauge plate to fix to the gutted cd tray that I will have water-jetted to final install the gauge as it is still just sitting in the opening.

I have extra components left to make three/four additional driver boxes. If anyone is interested one PM me. I would supply a complete box, harness, DME signal tap wire, ties, etc with all connectors and fuse.