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Old 07-25-2003, 12:50 AM   #1
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Default Tricked IAT Sensor

Well with all this hot weather, a couple of weeks ago I decided to try the resistor trick with my Intake Air Temperature sensor.
I bought a .50 cent 4.2 K ohm 1/2 watt resistor and plugged it into the wiring harness that used to connect to the stock IAT sensor.
It is supposed to trick the PCM into thinking the air temp is 58 F and give an extra 1 1/2 degrees of timing advance.
I don't have an Autotap but there haven't been any problems or lights / codes flashing.
The Bonne seems to be running great. even with 90 F outside temps.
Has anyone tried this trick and tested it with a scan tool ? Dbtk2 ?
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Old 07-25-2003, 01:09 AM   #2
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I tried it awhile back. Only took my PCM about 2 hours to relearn and fix the changed reading coming from the IAT. Meh...
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Old 07-25-2003, 02:34 AM   #3
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You can't trick your MAF and O2 sensors. Your PCM will outsmart you in time. That resistor was cheap anyway. All these sensor inputs work together. Trick them all, or don't bother.
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Old 07-25-2003, 02:35 AM   #4
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What about the Mini-afc that plugs into the MAF thought Bill? Or is that not consideried "tricking"?
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Old 07-25-2003, 03:48 AM   #5
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Quote:
Well with all this hot weather, a couple of weeks ago I decided to try the resistor trick with my Intake Air Temperature sensor.
I bought a .50 cent 4.2 K ohm 1/2 watt resistor and plugged it into the wiring harness that used to connect to the stock IAT sensor.
It is supposed to trick the PCM into thinking the air temp is 58 F and give an extra 1 1/2 degrees of timing advance.
I don't have an Autotap but there haven't been any problems or lights / codes flashing.
The Bonne seems to be running great. even with 90 F outside temps.
Has anyone tried this trick and tested it with a scan tool ? Dbtk2 ?
Yes, I have tried it, only we were stupid enough to buy the actual product from SLP for a $25 rip off. (for a total rip off of $50 because we bought 2 of them) But anyways, it tricks the air intake temperature into being 43 degrres (and it actually does, it is always 43 degrees on the scan tool). All it does for you is makes your timing run 17 instead of the normal 15 or 16. If the conditions are right it will hit 17 without it, but rarely. BUT...The problem is it will cause KR if your car already has it or is right on the edge of having it without the resistor because it is running more timing. It makes it really hard to tune the car if you need to because the computer is getting odd readings, but it does do what it is supposed to. We don't mess with it on either car, because the GTP always runs the full 17 degrees of ignition timing because of how the PCM is set up, and it doesn't seem to make a difference on the SSEi, so we have 2 of them setting on the shelf in the garage. I could do some more testing, because I really wasn't trying to figure out what the exact differences were with or without it, but I can if you guys want. But, I would think that if you weren't getting KR, and weren't seeing full ignition timing (which you usally aren't), it could give you ~5hp. If you know your car isn't getting full timing, and isn't getting KR, then it would be a good mod, but if your car is getting full timing, or is getting KR it won't help, and if it is getting KR it will probably hurt a little. It is a good mod for the track, but for everyday driving it probably isn't good, especially since, as willwren said, the PCM will learn it, and ignore it, and you lose all benefits.
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Old 07-25-2003, 03:52 AM   #6
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doesnt that just make it run leaner or richer? because of the air temp that it thinks is coming in to the actual air temp comin in? isnt htat what you told me will?
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Old 07-25-2003, 03:58 AM   #7
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Quote:
doesnt that just make it run leaner or richer? because of the air temp that it thinks is coming in to the actual air temp comin in?
Yeah, that and gives you full ignition timing. It makes it run richer. This is why it makes it harder to tune if you have one. They are more trouble then they are worth IMO, that is why both of ours are sitting on the shelf.
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Old 07-25-2003, 03:21 PM   #8
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Quote:
Originally Posted by dbtk2
Quote:
doesnt that just make it run leaner or richer? because of the air temp that it thinks is coming in to the actual air temp comin in?
Yeah, that and gives you full ignition timing. It makes it run richer. This is why it makes it harder to tune if you have one. They are more trouble then they are worth IMO, that is why both of ours are sitting on the shelf.
Agreed.
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Old 07-25-2003, 05:11 PM   #9
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dbtk, I won't rip on you for buying one. I would have, if I hadn't known what I know first.....or seen someone else learn the hard way. For a quick track run, I can see the benefits. Absolutely. For that reason, I'd do what you did. Put them on the shelf and save them.

Just out of curiosity, what'* the resistor value on them? I'm assuming about 6 or 7k?

For anyone else considering this mod, if you INSIST on doing it, don't buy the crap off of ebay. Buy a resistor and do it yourself, but I'd suggest buying a scantool first. You'll need it, or you won't know what'* going on.

One of the things I was considering was a 'bypass switch' in the cockpit. Flip it to bypass, it inserts a resistance in place of the IAT. For everyday driving, leave it in the IAT mode. Running it full-time isn't practical.
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Old 07-26-2003, 12:26 PM   #10
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Quote:
I could do some more testing, because I really wasn't trying to figure out what the exact differences were with or without it, but I can if you guys want. But, I would think that if you weren't getting KR, and weren't seeing full ignition timing (which you usally aren't), it could give you ~5hp. If you know your car isn't getting full timing, and isn't getting KR, then it would be a good mod, but if your car is getting full timing, or is getting KR it won't help, and if it is getting KR it will probably hurt a little.
Yes, please do some testing. That'* why I posted. Because I don't have a scan tool.

When I first heard of this trick, it was recommended as something to do only for a quick track run. I didn't know that the PCM would eventually learn to ignore it if left in for a long time.


[/quote]Just out of curiosity, what'* the resistor value on them? I'm assuming about 6 or 7k?
Quote:

4.2 k ohm 1/2 watt
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