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Old 02-06-2010, 09:13 PM   #1
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Default Major Coolant temp discrepancy

For about the last year I've become pretty concerned with the high temp readings Megasquirt reports on Andy's (Crnrhrd) car. Cruise on a 70 degree day with factory cooling system typically reported 210 - 215+ degrees on a naturally aspirated motor. Recently he upgraded to a Godspeed radiator, 160 degree thermostat, even replaced the temp sensor for the ECU and nothing changed. The radiator is full of distilled water only along with water wetter, still doesn't make any difference at all. Noticed recently using TunerStudio we're seeing 230 degree water temps after a high boost highway pull and I'm really not sure whats going on here.

The other day we started the car and brought it up to temp. Megasquirt was showing 190 degrees CLT but my thermocouple dropped into the radiator filler neck gave me a 168 degrees. This really screwed me up, so I reflashed the firmware to MS and it didn't change anything at all.

Is this difference in temp between whats in the radiator's filler vs the rear of the head part of the Miata's factory cooling routing problem or is there some underlying problem here that we're both overlooking?
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Old 02-06-2010, 09:21 PM   #2
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Which MegaSquirt system? Could be a sensor calibration issue.
Where exactly did you put the t-couple? I'd fully expect (and hope) that coolant in the radiator would be less hot than coolant in the back of the motor.
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Old 02-06-2010, 09:23 PM   #3
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is the IAT reading high too? Are the two more or less in sync when starting cold? Reflash with new easytherm files?
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Old 02-07-2010, 02:38 AM   #4
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Have to check the temps fully cold, haven't done that yet.

Its a PNP from DIY, I even downloaded their software and tried to reflash it again with a fresh image. I'd expect a temp difference too between the back of the head and radiator, but 22 degrees?

I tried to be careful about how to insert the thermocouple, made sure it was about 2" inside the filler neck on the radiator making sure not to touch actual metal.
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Old 02-07-2010, 03:03 AM   #5
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Flashing only won't cure the problem, you need to do the temp sensor calibration - the values for that are also at the DIYPNP page.
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Old 02-07-2010, 11:26 AM   #6
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I found this. Zaphod, where are the known values that can be used?
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Old 02-07-2010, 12:33 PM   #7
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Old 02-07-2010, 01:55 PM   #8
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Thanks

I just went through all of the menu options on TS, and I can not find 'Calibrate Thermistor Tables.' I am not seeing it under 'Tools.'
I also checked in the mainController notepad.

I have the most recent update of TS.

Quote:
Again from TunerStudio, click 'Tools > Calibrate Thermistor Tables'. Make sure 'Coolant Temperature Sensor' is selected at the top.

For the CLT, use the following table with a bias resistor setting of 2490 ohms:
Temperature F / C Resistance In Ohms
-4 / -20 16150
104 / 40 1150
176 / 80 330
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Old 02-07-2010, 04:37 PM   #9
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Calibrate Thermistors is only an option for MSII, with MSI you must build the tables within your firmware upload file using Easy Therm.

You thermfactor, matfactor, and airdenfactor.inc, in your mtcfg folder of your project, must match the firmware you have loaded on your MS.

if you're running Tuner Studio, those files must be copied into the INC folder on of your project.
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Old 02-07-2010, 05:59 PM   #10
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I opened up EasyTherm, and there were the tables for both coolant and ait.... Then I started reading through some of this and Scott's last post, and I want to shoot myself

I am probably going to have to stick with the 'square peg, round hole' philosophy. I do not see good things happening if I start screwing around with EasyTherm.
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Old 02-07-2010, 11:25 PM   #11
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you can ruin things fast. you shouldn't ever need to mess with it.
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Old 07-24-2010, 09:31 PM   #12
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Quote:
Originally Posted by Zaphod View Post
what values are used for the GM IAT on a 1.6?
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Old 07-25-2010, 04:34 AM   #13
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This thread is about the clt but anyway - use the standard GM values you get in your MS software (megatune/easytherm or TS)
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