Megasquirt coolant flux issues.. Autometer says 160-170, MSnS says 190-220?

[Slow_Old_Car]

Had a recent development w/ my MSnS system, this is a 029q2 MSnS-E on a v2.2 board w/ map daddy 4 bar, 440cc third gen supra turbo injectors, and GM IAT and CLT sensors.

 

Was driving around last night and kept seeing 200ish degree's on the computers MSnS readout, but the autometer sport-comp gauge was reading 160-170 (with a 160 thermostat).

 

During some engine datalogging i even saw 238 at one point which has me thinking the MSnS sensor readings are on the fritz, but what check or adjustment is there on stock GM sensors... i know easytherm and the likes is around for using stock nissan sensors, but i'm unsure what to make of this issue.

 

Should i reinstall MSnS-E? Reflash the MSnS box? Etc...

 

Since both sensors draw there readings from the tapped and threaded thermostat housing i'm going to begin with pulling them out and doing a bench test with a thermometer to see which sensors closest, but i'm open to ideas... just about had a damn kitten when i saw that 238f in the engine logs.

[Tony D]

Better to do a pin to pin check from the connection at the MS, and then at any juncture heading back to the sensor, culminating with a sensor resistance check.

If you get a noticable drop in resistance as you work toward the sensor, the connection you just eliminated is your problem.

 

It's not uncommon for resistance to build up in connections, and cause false readings. Skews them high or low, depending. Unless they are both drawing from the same sensor, likely they will be different---but not that different!

 

Somewhere you should be able to dig up a resistance-to-temperature curve for the sensors. That will tell you the range you should expect to see during your troubleshooting.

 

Many times people skip to sensor, when it's a harness connection that is the problem. Doing the pin to pin checks the whole loop first, and then you eliminate pieces as you go towards the sensor.

 

Good Luck.

[mario_82_ZXT]

Where are the temp senders in relation to each other? If you are running the megasquirt one through the CHTS, it is slightly hotter there.

 

Also, if you are doing this, you need to use EasyTherm to make a custom firmware since the resistance curve is different then the GM sensor MS was made to use.

 

Mario

[mobythevan]

If it has always been high and you built the board maybe the wrong resistor was installed on the board and the calibration is off.

[Slow_Old_Car]

Where are the temp senders in relation to each other? If you are running the megasquirt one through the CHTS, it is slightly hotter there.

 

Also, if you are doing this, you need to use EasyTherm to make a custom firmware since the resistance curve is different then the GM sensor MS was made to use.

 

Mario

 

Both senders are tapped into the thermostat housing, so there source for both is the water just under the theromstat inside the housing. Ones the sender from autometer for the gauge, so it should be pre-calibrated for it's gauge, and the other is the recommended GM CLT sensor that MS is pre-programmed for, so again it should need no adjustment. Right?

 

If it has always been high and you built the board maybe the wrong resistor was installed on the board and the calibration is off.

 

I've been running the system for a few years, and i want to say it was right on the money back in the day, but who knows... but i figure going down the highway with 10.8 AFR's trying to cool it down on a evening ride and still seeing 200+ on the PC while the autometer reads 160... one of em has to be lieing.

[randy 77zt]

i am always a little crude but i like to keep it simple-stick a thermometer in the radiator neck and compare readings?i run 165 thermstat and usually see 175 to 180 on my ms around town.

[z-ya]

i am always a little crude but i like to keep it simple-stick a thermometer in the radiator neck and compare readings?i run 165 thermstat and usually see 175 to 180 on my ms around town.

 

I find the MS readings to be very accurate. I have a 192F thermostat in there, and it usually reads around 189F.

[Slow_Old_Car]

initial tests are inconclusive. started tonight with pulling the thermo housing off, found the underside covered in suit (i keep a fairly clean motor), so part of my "overheating" readings might be exhaust gas passing the gasket and basically hot plating the thermostat housing.

 

however, just to be sure i took both senders out, started off with a water test... with baseline devices being a infrared therometer for checking brake temps, and a digital oral thermometer. testing situation was a glass of water.

 

the oral thermometer wouldn't read above 110, the MSnS sensor was close to that, and it barely registered on the autometer since it's a 100-250 sweep gauge, the infrared kept getting mixed readings since it reads a larger target area and averages.

 

in efforts to establish a higher temperature baseline to see if it got inaccurate the hotter it got, out came a butane torch, again the infrared was worthless since it couldn't finite down enough, but up untill the point we pegged the autometer things seemed to be halfway accurate.

 

i really think the problem is going to be the exhaust gasket as my MSnS sensor is the lower sensor of the two in the housing and would have been the most succeptable to heating of the thermostat housing.

 

in addition to that it appears the alternator is dead, so i've pulled that out to take and have tested, initial results w/ a ampremeter on the outputs of the alternator were not encouraging. i spent some time diggin through the atlantic z car tech tips on wiring a ZXT alternator into a S30 car, my wirings definately not right, but i cannot distinguish my wiring colors after several decades of heat discoloration either. so it will probally come down to trial an error.

 

this "2 hours of downtime" may become a week in very short order...