My solution for Oiltemp and Oilpressure input into Megasuirt (MS3)
 

Hi folks,

after a long time with no time for stuff like that I took the time to bring on my attempts to get the oilpressure and oiltemperature into my MS3.

I think there were already various threads about that stuff - but mostly using resistive sensors and using a pullup inside the MS. Problem with that is - most of the sensors have a sensor curve and not a linear behaviour.

I did like to go the easy way and get "easy" 0-5V llinear signals into the MS.

So here is my solution:

Oilpressure:

... is indeed quite easy - (especially for you US guys) - I used the Auber 5 BAR (75 PSI) Gauge Pressure Sensor, 1/8NPT

5 BAR (75 PSI) Gauge Pressure Sensor, 1/8NPT [AUBER-P205g] - $63.00 : auberins.com, Temperature control solutions for home and industry

https://www.miataturbo.net/attachmen...ine=1443431746

Connecting is easy
+5V from MS Vref
ground from MS
signal wire into one of the analog inputs

Now you have to tell the MS what input it gets and what the meaning of the 0-5V values is:
So - it's oil pressure, -0.6bar at 0V and 5.6bar at 5.0V - as to be seen here:

https://www.miataturbo.net/attachmen...ine=1443431746


Oil temperature:

... is a bit more complicated
All the common sensors (NTC) use a sensore curve and are not linear - like this
https://www.miataturbo.net/attachmen...ine=1443431746

As the Megasuirt only has very few 3-point sensor calibrations - this would lead to a big deviation on most of the temperature curve.

This lead me to the PT100 sensors - linear, highly correct temperature sensors. (in 2, 3 or 4-wire layout to delete the resistance error of the wires)

But - you need an evaluation board to get a "correct" signal out of this sensor for the megasquirt. (As I said 0-5V preferred in my case)

Well, I found a solution for this for reasonable money:

the sensor:
Again - lucky US boys:
Oil/Water Temperature Sensor, High Precision [PT100A-NPT] - $28.50 : auberins.com, Temperature control solutions for home and industry

This sensor is not easily available in Germany - so I did use this:
Temperaturfühler mit 2m Zuleitung ...105 Grad - Pohltechnik

And this is the evaluation borad DIY kit (sorry only in German, but I think you will find something like this in the US too)
Bausatz PT100 Messwandler - Bausätze / Module - Bausätze - - Pollin Electronic

Problem for me was the M6 thread of my German sensor - I had to make an adaptor with one of my sandwich plates 1/8 NPT blinds. Drilled, tapped and shortened a bit to hold the M6 sensor. (unfortunately there is no 1/8 NPT male to M65 female adapter available)

The evaluation board is a DIY kit - so some soldering required
https://www.miataturbo.net/attachmen...ine=1443431746

The board needed a case - luckily I had an old mini-screwdriver case around with a perfect fit. Some self-adhesive velcro and it's mounted on the tunnel behind the center console.
https://www.miataturbo.net/attachmen...ine=1443431746
https://www.miataturbo.net/attachmen...ine=1443431746

Setting up the evaluation board needs some patience - I used a variable resistor to set the upper and lower measuring range and according output.

I got the 5V to feed the evaluation board from an automotive adaptor for mobile phones - but as the board only draws 30mA I think it could be fed through the +5Vref out of the Megasquirt too.

Now I made myself 2 new gauges in my TunerStudio dashboard
https://www.miataturbo.net/attachmen...ine=1443431746

And this is it - now I can log and read the values in TS/MS.

In MS3 there is even a warning function with minimum oilpressure over rpm and a warning light output.

I thought this might be of some relevance for some of you on here...

These are what I will be using for oil pressure and fuel pressure:

Pressure Transducer or Sender 100PSI for Oil Fuel Diesel Gas Air Can'T for Water | eBay

Wired up to the Spare ADC no circuit is needed.

Then there is a saturn 1/8npt that can be hooked up to ms also. Just needs a 2.49kOhm pullup to 5v (I believe?)

You could use a GM coolant temp sensor for oil temp, choose the option for "GM calibration" for your sensor transformation, and win at oil temp readings for like $20 and no drama.

Thats the saturn one. Its the only 1/8npt I can find. I picked up a couple pigtails at the JY today.

And I still need to add the bias resistor.

Problem for me is to find parts like that over here in Europe...

I did try to find the "easy solution" Dayco/GM coolant reroute recently - no way in hell to find this here...

Does china not ship for cheap to Europe?

This is what I am doing. I need to order another pigtail from you guys for the one I have.

Psh. My IAT sensor / Oil temp sensor came from LKQ lol.

Where did you put a 3/8 NPT sensor?

I'm unsure who you're addressing here, as there hasn't been any mention of 3/8 in this thread.

I did not know DIY sold a 1/8 npt coolant sensor.

I used this bung with this temp sensor. The bung is welded directly above my oil drain hole.

Ah yes, yours is in the oil pan.

Mine is in the sandwich plate, much smaller hole.

Kinda late on this but doesn't Mazda use BPT threads and not NPT threads? If so Aidan, get an adapter. From some research BPT and NPT have the same thread and thread pitch but the thread rise has a different angle.

This is going in my sandwich plate which is NPT.

I stuck an 1/8 npt coant sensor in the stock gauge location which is 1/8 BPT. No issues at all.

Find me a converter that works for coolant temp and I would have bought it for sure.

I'm traveling back to Germany usually two or three times a year. If you need parts that can easily fit in a suitcase, I can hand-carry them over for you.

It sounds like you've got it covered, but another option is to use CAN bus. A cheap sensor, an Arduino with a CAN bus shield, and a teeny bit of software and you should be able to linearize any sensor you want and put it into the megasquirt as a generic "CAN ADC". Similar to an IO box, but a lot less expensive.

--Ian

Tinyiox has 9adcs. Has some PWM outputs, and digital wideband in.

For $75. I couldn't argue with that.

OK, for some reason I thought you needed to buy a $400 microsquirt board to use it. A cheap clone arduino & can shield is probably $20-30.

--Ian

It's standalone, hooks up to ms3.

The wideband interface is what sold me.