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Old 12-04-2007, 11:02 AM   #1
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Default CLT/MAT Discrepancy - What's normal?

So with my Coolant issues fixed, R7 Removed, the Firmware re-flashed with the RX7/GM settings I think I'm ready to go.

However I'm noticing a difference of about 9-11 between my CLT and my MAT (CLT is the low one) in the morning when I go to start my car. Initially I thought it was just the coolant and the engine block holding temperature better, but I'm not sure it ever hit 9 degrees last night.

So I ask, what's normal? Hate to be futzing with my Crank settings only to find out that my CLT is too off to get good settings.
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Old 12-04-2007, 11:24 AM   #2
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Your engine should run above your thermostat temperature. My car runs around 190-200 in normal driving. Thats with the stock radiator.
IAT's should be close to ambient but that all has to do with your intake ducting and where you are getting your air from. If you have a good cold air setup like Scott's naca duct headlight lid you could see ambient IATs all the time. If you have your filter against the radiator, then expect them to be warmer.
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Old 12-04-2007, 11:34 AM   #3
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Quote:
Originally Posted by cjernigan View Post
Your engine should run above your thermostat temperature. My car runs around 190-200 in normal driving. Thats with the stock radiator.
IAT's should be close to ambient but that all has to do with your intake ducting and where you are getting your air from. If you have a good cold air setup like Scott's naca duct headlight lid you could see ambient IATs all the time. If you have your filter against the radiator, then expect them to be warmer.

all valid, but the OP stated the temps differ first thing in the morning, and I assume prior to starting the car?

I'd agree there there is an issue, tho I don't know what to suggest. I'd firstly try reloading the firmware and working from there.

You may have a duff sensor.
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Old 12-04-2007, 11:40 AM   #4
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my AIT was reading about 20 less in the morning under 50, wasn't helping starting the car.

the best way to solve it is measuring the actual resistance your AIT puts out. its as simply as submerging the sensor in luke warm, ice cold, and boiling water (only submerge the part that reads) measure the resistance with a multimeter and burn these resistance values. Hopefully it's closer. if not, then you may need to do the same with the thermosensor. make sure your fans turn on at the designated temp 207F IIRC, if it's off by much, then reflash those values, however, the CLT has little effect of fueling after warmed up, so if it starts fine and it's relatively close once everything is warmed up, then don't worry about it.

IIRC, the resistance range for the factory thermosensor at -4F is between 14600 and 17800ohms. That's a pretty big wiggle room to get things off by a few degrees. The values you flashed are the averages of those two...
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Old 12-04-2007, 11:43 AM   #5
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Are you using coolant temp, iat, or are you averaging the two in your cranking settings? I used to average my temps and it caused all kinds of problems. When i base my cranking off just coolant it works perfect. Even if there is a temp differential across the two sensor up to 20* due to heatsoak or if the motor is still cold from a 30 degree night but the air has warmed up to 50*.
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Old 12-04-2007, 03:51 PM   #6
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I know my sensors were about 4c or was it 9c... different. I think the smaller. I didn't bother going to the length of measuring the sensors themselves and figuring it out... it wasn't worth it to me.
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Old 12-05-2007, 11:47 AM   #7
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Quote:
Originally Posted by cjernigan View Post
Are you using coolant temp, iat, or are you averaging the two in your cranking settings? I used to average my temps and it caused all kinds of problems. When i base my cranking off just coolant it works perfect. Even if there is a temp differential across the two sensor up to 20* due to heatsoak or if the motor is still cold from a 30 degree night but the air has warmed up to 50*.
CLT only. Seems to be a consistent 11 degrees thus far. (And often the temp is lower than the low that night.) Complete with fans kicking on ~189 or so. It's starting up quite fine as I'm getting it dialed in in the Crank settings. I may not worry about it. 11 degrees is just right on the border of "Could be annoying" since it gets over to the next field. Would prefer it was 5 degrees or best yet, none.

I may reflash and see if that alleviates my problems.
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Old 12-05-2007, 01:14 PM   #8
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checked mine today, 40 CLT, 41 IAT before I started it.
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