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Air intake temperature SOAR when I step off the gas.


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hi!

six shooter, i pulled the sensor our.  this is it: 

post-49697-0-12892200-1433819366_thumb.jpg

 

Stamped on it are:

Delphi

1938

ACr-12v-3

 

From that and google searches, I can confirm it's a GM model, and it's an open element.  It's basically what the megamanual orders (my card is megasquirted).  To be certain that all worked properly, I did some calibration tests as per these instructions http://www.diyautotune.com/tech_articles/iat_clt_resistance_curve_calculation.htm and that gave me the right output for a GM sensor... 

 

Word to the wise: do it like the link above says, it's much faster and much less fussing around (I used a soldering third had to hold the sensor in the water;  I tried hand holding it, but I wasn't able to hold it in the steam and connect the probes to the sensor at the same time).  I tried (before following the instructions, I was worried about dunking an open element sensor in water) with a cheap digital thermometer and a hair dryer pointed at the sensor, but the thermometer was not precise enough and the range of temperatures was not wide enough (+-82 to 140 farenheight).  Then I put the sensor in the fridge, but the temperature was all wrong by the time I'd managed to get a solid connection with the multimeter probes...

 

After all that, I put the sensor in the car and started her up;  the temp reading was exactly the ambient temp, suggesting that it's well calibrated.  I checked to see what the setup was on the thermistor calibration page for my megasquirt, but the current setup is not available, only what you could possibly set it to.....  just to be certain I'll set it up for a GM sensor...  if you don't hear me say in a few days that it's solved the issue, then that means that didn't help (it's going to be raining for a few days here, so no driving'  I've got a big gaping hole in the pass. floor that i'm working on and I'm pretty certain there is a leak around the windshield)...

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I use the same sensor in the same location and it was always sooty when removed or missing the little plastic sensor tip that is in the cage. I kept having problems and moved it to the intercooler pipe before the throttle body and the temps are much lower because its not being heated by the intake manifold and i have not lost anymore sensor tips sense. Anyways its much more consistant in the pipe than in the manifold. Best of luck pal.

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red zed.

 

when you moved the sensor to the intake pipe before the throttle, you got more constant temperatures..  but does the car run as well?

 

What i mean is is the temperature reading just as useful to the ecu?  I'm still not 100% certain if the spike is heatsoak or if the air temp actually goes up (or both).   I'd be worried that changing it to a more stable temp area might screw the actual calculations....?

 

s.

 

PS: it might help me with another problem i've experienced, that I believe is due to temp readings;  if I use the car multiple times within a day when it's somewhat hot (above 25C/77F), I get really rich AFR (around -2 afr on average) for the drives after the initial ones.  I suspect heatsoak, although I haven't noticed the sensor readings to be higher while driving...).  

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  • 2 months later...

thanks red zed.  

 

I've got some significant other issues that cropped up lately (I believed issues with my injectors, my oil pan is out as i'm replacing the gasket (here is the link for what i've been diogn. http://forums.hybridz.org/topic/123168-changing-oil-pan-gasket-on-l28et-with-engine-in-car/), and I just fixed the passenger floor)...  

 

but definately, i'll look into what you suggested. I don't like what it's doign, and i'm pretty certain, down the line, it could screw things up a little if I manage to fine tune the car on a dino. 

 

Thanks to everyone who posted..  I'll try to post if I ever get around to changing it...

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  • 2 weeks later...

I agree that the point used was a terrible one!
Intercooler piping is much more preferable.

The reason you were getting the temp spikes was 'heat soak'--you started reading ambient manifold temperature and not really air temperature. Putting it in the plenum portion, or intercooler pipes would have less of this effect.

 

I put mine in the T/B Adapter right behind the throttle plate shaft so it doesn't interfere with anything airflow-wise!

Edited by Tony D
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  • 1 year later...

so it's been a full year since anyone wrote here.   this is a bit of a resurection, but there is a good reason for it. 

 

I 100% figured out what the problem was.  well., I didn't figure it out.  i fixed it.  

 

Pretty much everyone was right: it was the location.  I had a friend weld a bung in the pipe right before the throttle body, and the temperature went from:

- anywhere between 100 and 200 degrees F, along with wild spikes based on when I'd open or close the throttle,

 

to

- anywhere between 60 and 100, with no spikes at all, and the temperature only slowly climbing when i'm stuck in traffic (which is probably a combination of very mild pipe heat soak and significant high temps in the engine bay, where i currently get my air).

 

I wanted to thanks the guys who did suggest I do this.  I also want to put out there that i don't think that the intake is a good location, no matter how well you tune for it (against it?).  Even if you use the air temperature correction thing to make up for heat soak, or the cold start enrichening (?) thing, you're going to correct for when the MS2 thinks it's hot, but if you ever actually do get some hot air, it'll screw your tune.  

 

Thanks again, and i hope that comes to someone's help in the future. 

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