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.

I understand your reasoning Joe for the department store bike, and after all your efforts I'm sure it's a decent commuter... But I can't be the only one thinking this.. Is such a cheap bike worth all the effort? I mean, have you found it to be worth the effort?

I know when I was a kid we all rode cheap Bikes, everywhere, and rode the crap out of them. I maybee had three different ones throughout my childhood, and all I remember doing is replacing tires and occasionally lubing the chain and that's it.. I guess combination of single speed and coaster brake means it can take abuse.

Someone scrolled down on mobile too far when responding.

Bump.

I have MSPNP Pro, am I going to have to follow this in order to have oil temp and pressure readouts? Did you still have your readouts in the gauge cluster?

There is no gauge cluster oil temp. As long as you don't remove the stock pressure sender you will still have it. But if your car is 94.5 or newer its a fake readout anyways.

Should've been less vague. Merely referring to the pressure readout on the dash. So there's a definite benefit beside having the gauge in the TunerStudio. That's what I was wondering.

Pressure readout on the dash is fake.

Also the temp readings for coolant are "fake" too right? I hear lots of conflicting info from various people at meets that say their temp guages are worthless and then I hear it only affects people with the NA.

It's not linear. There are ways to linearize it.

So I've heard. I wish there were ways to search and get results back that highlighted where it detected your keywords. Being a newbie these days is tedious as hell.

I built an Arduino based linearizer a while ago. Others have done similar things. Schematic is in this thread: https://www.miataturbo.net/megasquir...-values-74383/

Good looking out. If I had one of those last year I might still have my car running.

Make a warning light. My check engine light is set to turn on when things get too hot.

I'll probably drill a hole in the gauge cluster so I don't confuse my CEL for something else. Did you just have it on a relay or was that something you programmed in MS?

The megasquirt controls the check engine light. So set it for whatever you want.

I control it with the megasquirt.

Sweet. How hard do you think it would be to add an auxiliary light control option? I doubt it would be difficult, I noticed some folks have shift lights controlled my megasquirt. Haven't been able to use any of the tools yet because my whole kit is sitting at the machine shop where my engine is.

rtfm?

Not hard. Read the manual. It explains everything.

:jerkit:

with that attitude, you're not going to last long on MT

No different than the attitude coming from someone who didn't read the part where I said "all of my Megasquirt stuff is at the shop with my engine block"

Plus aidan was an adult about it unlike stefanst. That being said, it's the Internet and everyone is more confident about being a dick toward other people for no reason so I didn't take it personally when I was told to "read the fucking manual" from someone who didn't even bother to spell it out. They get an emoji in return, everyone goes on their merry way. Judging by the attitude of some tenured posters I'll fit in just fine lol.

You got lucky. I was having a good day. I'm normally the asshole.

That being said I hate answering questions that have been answered before.

And so does everyone else. Keep a thick skin and be an asshole back. But read the fuckin manual first.

I get that. I come from MazdaspeedForums so I hate being "that guy". Nobody here is even coming close to the fuckery one has to endure on that forum hahaha. CodeMonkey knows all about MSF you've probably seen him floating around MT a bit too hahaha.

Digging up this thread since this has been one of the top results when lookup up adding Oil Temperature sensor to megasquirt.

The 1/8" NPT GM sensor (which you can screw into the sandwich plate) has a part number "TX73T". It should come up in any search as a coolant temperature sensor. DMed Aidan to get this info.

They should be super easy to find on ebay, available for global shipping for <30$ shipped.

I am unable to find connectors or pigtails online, so unless you can get a junkyard pull I would recommend just soldering wires to the pins, then potting the sensor for extra reliability (I just used some Permatex as its somewhat flexible and assume will be better)

Attachment 232777
(a bit dirty before I cleaned up the soldering, make sure its nicely soldered, I just grabbed the thing by one cable at a time and spun it as fast as I could to ensure it was decently solid)

Attachment 232778

I then shrink wrapped it for extra strain relief of the cables, and added some nylon mesh for less shitty looks:

Attachment 232779

Couldn't get a good view of your connector pre-wired. No Amazon?


for this sensor

Its a really small connector https://www.ebay.com/itm/Standard-Tru-Tech-TX73T-Air-Charge-Temperature-Sensor/380449766421?epid=74407271&hash=item589492bc15:m:m RkUJ19XUBUG8Y0mQAFk_vQ:rk:1:pf:1&frcectupt=true

Its really hard to have an idea of sensor connectors online sometimes lol.

This one is round, with a locating tab. In my picture I cut off a bit off the tip so it sat flush with the top of the pins for easy soldering. You could also use some normal pin connectors and pot it, I guess.

I understand. That same sensor is listed for a Saturn SL coolant temp and would use this pigtail FYI: Saturn SL Engine Coolant Temperature Sensor Connector Dorman 62942MQ

i just go to junkyards and grab them off sl's. They are a dime a dozen here.

I think @afm had a better 1/8npt sensor with a "weatherpack" style connector.

So triggered. I personally use the TX73 above with a pigtail off RockAuto (Standard S1170). I paid $16, looks like they're $21 now.

Delphi makes the 12160855 fluid temp sensor, which is 1/8 NPT and uses an unsealed Metri-Pack connector. However, it uses a different curve from normal "GM" sensors --- the resistance is ~4x as high at every temp.