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Old 12-09-2007, 12:42 PM   #1
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Default Very wierd heatsoak issue.

You guys are gonna love this one.

I have my AIT sensor in the plastic cross over pipe maybe 3 inches away from the throttle body. I start the car, it idles perfectly, warms up perfectly, at 160 the WUE turns off. Everything is just how its supposed to be. The AIT slowly rises as the car warms. Sometimes it settles around 70, and sometimes it keeps rising. The car continues running perfectly though. I can even go for a drive and it will drive totally fine.

As soon as I stop and turn the car off, then immediately turn it back on at idle the AFR's are full lean. The hover around 18. Mind you, just 30 seconds ago when I stopped it was idling perfectly.


First, when AIT's increase shouldnt the AFR's become richer and not leaner?

Two, disconnecting the AIT, which causes the sensor to default to -40 according to megatune, will make the car run flawless again. Soon as I plug it back in, AFR = 18.

Three, How fast should the sensor respond to temperature changes? it seems like mine barely responds when I take it out of the crossover tube and just blow on it in 32C weather.

I have no clue what this could be. If I start the car the first time, and let the temps get to 70F then go for a drive its fine. Everything goes AWOL when I stop the car, and re start it.

To rule out possibilities of heatsoak I have moved my sensor away from the throttle body and into the snorkel by the firewall. Havent experimented with this yet. Probably tomorrow.
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Old 12-09-2007, 12:50 PM   #2
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do you have the updated easytherm values from DIY?

i just did some air intake temp testing on my daily driver with a megasquirt pnp with IAT sensor. 70 degrees or higher does not seem hot at all for a car that is idling. mine will go over 90 when sitting long enough on a day when it's in the 50's. and my iat sensor is in the stock airbox opposite side from the header. as soon as i start driving it'll drop. and that car has factory header with the factory headshield.

check out my thread about intake air temps over here http://www.miatamob.org/mobs/1/board...ics/273?page=1
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Old 12-09-2007, 12:52 PM   #3
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just noticed you're in brooklyn, i'm in the heights 2 days a week visiting my girlfriend. maybe we can meet up and have a look
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Old 12-09-2007, 12:58 PM   #4
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Brooklyn Heights? Where abouts? I mean sure, if you are here on the weekends great. But otherwise I get home from work kinda late, and have no light in my garage or heat.:(

What updated easy term values from DIY? I used the ones in the easytherm program for my sensors.
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Old 12-09-2007, 02:40 PM   #5
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ir goes lean with hotter intake temps.


i have my AIT correction kicking on above 85*F when i shut my car off i see upwards of 120*F in my intake and it fails to start being so lean.
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Old 12-09-2007, 03:43 PM   #6
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Do you recommend I turn on correction? I mean is this a prevalent problem?

Also, the leanness only occurs at idle, once I give it some gas it passes. I figure I can give it correction between 900 and 1500 rpm and it should be fine. I am just uncertain if this is the correct way to solve this problem.
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Old 12-09-2007, 03:51 PM   #7
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I think you need to try the sensor in your airbox before messing with corrections.
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Old 12-09-2007, 03:56 PM   #8
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I am gonna leave the sensor in the snorkel, its easier then taking the box apart. Then ill mess with corrections.
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Old 12-09-2007, 07:53 PM   #9
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Quote:
Originally Posted by Saml01 View Post
Brooklyn Heights? Where abouts? I mean sure, if you are here on the weekends great. But otherwise I get home from work kinda late, and have no light in my garage or heat.:(

What updated easy term values from DIY? I used the ones in the easytherm program for my sensors.
Clark and Henry. Before you get your hopes up the red 94 with white stripes I drive up there is my non-turbo one.

Jerry had sent me updated firmware with a fix for incorrect values for the IAT sensor. He was integrating it into the software after that. this was back in Oct. when is your firmware from?
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Old 12-09-2007, 11:50 PM   #10
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Quote:
Originally Posted by paul View Post
Clark and Henry. Before you get your hopes up the red 94 with white stripes I drive up there is my non-turbo one.

Jerry had sent me updated firmware with a fix for incorrect values for the IAT sensor. He was integrating it into the software after that. this was back in Oct. when is your firmware from?
My firmware is the 029v and I did the AIT myself and recompiled.

BTW, the AIT is correct. It shows exactly what my digital thermometer in my house shows. So that is no longer an issue.

My CLT on the other hands is waaaaaaaay off. But thanks to Cjernigan for finding a thread by Arkmake, I know now that for my 97 I should use 1205 ohms for my bias resistor.

The rest is just heat soak which I will use correction to fix.
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Old 12-12-2007, 07:19 PM   #11
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It wasnt heatsoak. Incorrect easy therm settings causing incorrect readings of the CLT were causing the problem. 1997 miatas use 1205 ohm bias resistors and that should be used in easy therm. After I flashed the new values, the car idles like a rock, fuel ratios are spot on, and it drives flawlessly.

Right now I get 215* when the car is fully warm. The temperatures dont go above that or below that, fans turn on in this neighborhood sporadically as well.

I think I am going to go to the mazda dealer and get a CLT from them to calibrate at home, then ill post up the correct easy therm values for the 97 cars.

What is the normal engine operating temperature? I am guessing fans only turn on to maintain this?

If this is the case, then 215 may be not that far off from the correct temp.
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