Slightly different IAT mod

[froggy81500]

After my first post and thread, here's the idea I was discussing with cheapybob.

I see a lot of ideas about modding the IAT signal with resistors to obtain a certain reading equivalent to a desired temperature to get a leaner mixture. The problem with using a resistor in parallel is that it doesn't change its value and will affect the IAT negatively in some temperature ranges, like the cold temperatures.

I studied electrical engineering for a few years. Adding resistance to a circuit is easy, just putting resistors in series and they add up. Lowering resistance is a little trickier. I played around with the parallel resistance calculations and came up with this idea.

Why not use 2 IAT's in parallel? Yes that is what you are reading. 2 IAT's that are resistors that will both be changine values at the same time. Effectively, what happens when two resistors in parallel of the same resistance effectively total half of that value. I did some calculating and compared them with the corresponding temperatures for given resistance.

this is what I found out. At 0F, the mid range of the IAT is 24K ohms. two of them would divide that in half to around 12K. That falls in the range for +20F. Effectively you are bumping up your IAT reading by 20 degrees.

Now at the high end. At 140F temperatures, the IAT mid range is 690 ohms. Divide that in half and you have 345 ohms, which actually falls between 160 and 180F, call it 170 ish.

One thing cheapybob alluded to was cold start drivability issues when using a resistor in the IAT. I think this dual IAT mod will correct that and maybe even work better than a resistor.

I also did some tweaking of the idea by placing a resistor in series with one of the IAT's to do some further adjusting of the ending resistances at several different temperature ranges.

Anybody care to chime in and ask questions or share ideas, please do. Also, what I'm really looking for is what temperature reading you guys try to obtain in order to maximize your fuel economy. If I know that, I can further tweak these numbers and give you possibly a better way to do it.