IAT sensor mod?
 

I don't understand what this might actually do... Surge Performance Chip by Surge Engineering Performance Parts

If you modify the IAT, you can modify the air flow (PV=nRT). But how can increase/decrease performances?

On some cars the ECU will use a different fuel map depending on air temperature. The lower the temp, the denser the air the more fuel it will burn. The higher the temp, the lower air density, less fuel will be injected

I believe it just alters the mixture, most likely making it rich, probably to rich. Too rich for MPG that is...

"Performance Chip", AKA "a resistor".

Scam-o-rama, all the way. Makes your fuel injection "think" the intake air is colder, so it fattens up the mixture a little. Until the O2 sensor sees that there's too much fuel, in which case it leans out the mixture again until it's normal.

In some cases, it may be enough to go "open loop", where the FI ignores the O2 sensor so you'll actually get that extra fuel all the time. Some extra fuel can result in a little teeny bit of extra power. More pollution and higher fuel consumption in that case, of course.

-soD

I've heard of people unplugging the IAT and replacing it with a resistor that gives the computer a value of 58 degrees in order to get more timing advance. But it's tricky because if the actual air temp is much higher this will cause knock and the computer will just pull the added timing right back out. There isn't a lot to be gained here. The only way I can see this chip being worth anything is if it can modify the IAT value to stay a set amount below actual temperature, as opposed to simply feeding a fixed value like the resistor trick. Still probably not worth it though.

Pure snake oil. Most modern ECU's are not that much affected by IAT temps. In fact, you will find that they will still operate in closed loop. Biggest thing they affect are total timing, as timing modifiers will add or take out a degree or two of advance according to temps.

The ECU pays the most attention to the O2's. And if the ECU richens the a/f slightly when it sees a cold IAT (or leans a/f slightly when it sees hot IAT) it will quickly figure out that something isn't kosher and KAMRF will correct those short term fuel trims, and eventually make them long term fuel trims.

And if it ignores it enough, it might even through a CEL telling you the IAT sensor is suspect.

Snake oil for power gains, and snake oil for fuel economy gains.

Thanks everyone. So we can increase virtually the temperature, the fuel injected will be less? Or at the end will be the same (based on the O2 feedbacks)?

Net result is zero gain.

Sorry those chips are scams and don't do crap

I'll add a counter point. I put 5.6K ohms of resitance on my IAT and found that in temps above 70 degrees I see a bit of timing advance which, in my timing advance starved ECU, helps a bit for mpg. It's not much of a gain, but it is positive and the resistance change is so small that the ECU doesn't learn it

Try this site for an explanation of what modifying IAT sensor output does.
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Hey thanks alot for the site. Very informative

Two observations about the IAT sensor mod:
1. The computer can't "learn" that you've altered the IAT signal because it has no baseline to refer to, the temp always varies. It just acepts the temp as OK.
2. With a colder IAT signal the computer does two lthings. It advances the timing and richens the mixture. When it does this it gets feedback from other sensors. The nock sensor will tell it if the timing is too far advanced and the O2 sensor will tell it if the mixture is too rich. In either case the computer will adjust settings for best motor operation. Final result: a correct fuel mixture with advanced timing, the prescription for better MPG