Microsquirt Coolant Temp Sensor setting

[walfreyydo]

Tuner Studio should allow you to compare your actual temps coming from the engine temp sensor, assuming its calibrated correctly, in the tunerstudio dashboard. You can just compare that to the gauge temps. No need to use a thermal gun to do this unless you dont trust what TunerStudio is telling you.

Secondly, within TunerStudio you can manually calibrate the temp sensor (as well as any other sensor such as intake air temp sensor and wideband o2, etc) using the curve values that have been listed previously for the OEM 944 DME temp sensor as well as listed on Clarks Garage. If you are using a different sensor, youll need to either manually test to get the curve values, or look them up online on the manufacturers website. You basically need 3 values of temperature and resistance in order to map a curve, and you just plug those in as shown (use the dropdown just for "Coolant Temperature Sensor"):



Looking at clarks the Porsche OEM dme temp sensor has the following resistances (you can also test this manually for any sensor using a hot water bath, a meat thermometer, and a multimeter):

59F = 3300 Ohms
86F = 1460 Ohms
176F = ~320 Ohms

Someone listed the BMW 325i DME Temp sensor as the following:

14F = 9300 Ohms
68F = 2500 Ohms
176F = 335 Ohms

Bias resistor value usually always 2490 Ohms

Seems pretty close, so its probably fine, but recommend always use the calibration for the temp sensor installed in the car... I mean why not? You have the porsche OEM sensor values freely available to calibrate off of and you can usually find these curve values for whatever sensor you are running.

Agree with previous comment about fan control. I am running megasquirt and I let the factory relay and system control the fans. No need to have mega/microsquirt handle this unless you have totally removed/stripped the factory wiring. Manually controlling through MS is fine, but if you are only running low fans, it could have implications for the car running hot while in traffic, or running AC (if equipped).

[Dare]

I just double-checked the engine temp readings on my car (86 951 with MicroSquirt) and confirmed that TunerStudio sees 81-82C when the needle is exactly in the center of the 80C line on the dash. This is with the stock Porsche temp sensor and the TunerStudio “BMW E30 325i” preset sensor calibration. Likewise, the fans come on around 94-95C engine temp. So looks like the engine sensor is maybe a couple of degrees high, but totally within acceptable range.

[Tom]

I just double-checked the engine temp readings on my car (86 951 with MicroSquirt) and confirmed that TunerStudio sees 81-82C when the needle is exactly in the center of the 80C line on the dash. This is with the stock Porsche temp sensor and the TunerStudio “BMW E30 325i” preset sensor calibration. Likewise, the fans come on around 94-95C engine temp. So looks like the engine sensor is maybe a couple of degrees high, but totally within acceptable range.

Which sensor does the MS read? Assuming it's the blue one, your test shows that the gauge sensor and DME sensor are both pretty darn accurate. I have the 83/93 thermoswitch in the radiator so I almost never see the gauge go above the half way mark. I get that the factory was ok with it running up higher, but I have an irrational attachment to lower temps.

[Drscottsmith]

Thank you all for the discussion guys. I am still seeing the same temp setup so am going to do some more work. To answer some questions:

Newly rebuilt engine - new hoses, thermostat, etc
New csf radiator
The original cooling fan wiring was toast, one of the reasons I went with ms to be able ton control fans. Original idea was to have arduino control a pcm controller for variable speed fans (can bus) but I have not gotten to that yet and just have a simple relay setup right now with fans either in or off at 180F - changed that down from 194F.

Gauge still goes up to almost the 100 line sitting in the driveway, so definitely higher than the “middle of the gauge”. MS is being fed (and thus fans) by temp 2 sensor (blue plug) and gauge is the other sensor through the 14-pin at the firewall.

I am still not sure I don’t have some kind of ground issue with the gauge path, as when I turn the lights on the temp gauge bumps up what is probably 4-5 degrees so I am going to start working through that and also pull the sensors and do the calibration check with hot water and a thermometer. Will report back.

[Wespa]

I am still not sure I don’t have some kind of ground issue with the gauge path, as when I turn the lights on the temp gauge bumps up what is probably 4-5 degrees so I am going to start working through that and also pull the sensors and do the calibration check with hot water and a thermometer. Will report back.

Mine does that too, so it's more than likely to be an issue with gauge grounding. My fuel gauge is also acting up, but that's at least partly due to the sender, E85 seems to leave a varnish that's not fun especially with the low resistance values of the sender.

[Drscottsmith]

Good day all -

Still have testing to do but another question until I get home from traveling…

Can I run the stock fans in an on-off high speed configuration using one relay for each fan temporarily?

My thinking is my aftermarket setup is just not moving enough air - the factory setup obviously will, I just won’t have the flexibility of low/high speeds or one or two fans at first.

Thoughts?

[Tom]

Good day all -

Still have testing to do but another question until I get home from traveling…

Can I run the stock fans in an on-off high speed configuration using one relay for each fan temporarily?

My thinking is my aftermarket setup is just not moving enough air - the factory setup obviously will, I just won’t have the flexibility of low/high speeds or one or two fans at first.

Thoughts?

You could wire the fans to run only on high or not at all. However, if the car runs hot while cruising at highway speeds (which is my understanding) then the fans aren’t the problem. The cooling fans are mostly needed at stoplights and stop-and-go traffic. While cruising, there’s more than enough airflow through the radiator. Unless you are really pushing the car hard (e.g., track duty, top speed run, etc.) on the freeway the engine temp should stay at or near the thermostat rating without the fans running at all. For a car that runs hot while cruising on the freeway, look for traditional cooling system faults -- clogged radiator, failing thermostat or water pump, low on coolant/trapped air, head gaskets, etc.

[Drscottsmith]

That makes sense Tom - will start checking when I get home.

[Drscottsmith]

Well I may have found the issue. Loose clamp on the hose from the head to the heater valve…tightened and let it warm up in driveway in got to just a hair above halfway revving at idle. Will drive it tomorrow and see if it behaves!

[Drscottsmith]

BTW…interestingly I had no leak there, apparently it may have been just loose enough to keep the system from pressurizing.