MardiGrasMax

iTrader: (14)

I have been kicking this around for a while. I want to throw it out for discussion.

What is the function of the IAT signal at the ECU?
Well, it tells the ECU the temperature of the intake air, duh!

What does the ECU use that signal for?
To modify the timing map?
To modify fuel map?
Or both of the above?
I bet it’s both. But I hope its just timing!

So, the ECU will give more timing and fuel for a colder reading?
And less timing and fuel for a warmer reading?

See what I'm getting at?
Do you think that our cars feel so much stronger in the cold just because the air is colder and denser? I bet its because the timing and fuel ratios are modified to take advantage of cold air.

So the sensor provides a variable resistance reading based on temperature. So do you think you could put a potentiometer in line from the sensor to the ECU and adjust the reading to make the ECU think that intake air is colder so it will bump up the timing and fuel? Perhaps?

But we would need a Techtom MDM-100 to truly verify this, anyone out their with the Techtom want to help?

I’ll tri it with out the Techtom, but since I don’t even have a shop manual I need some one to tell me if there is a chart in the manual that shows the effect of the IAT sensor? And, what the test procedure/readings are on the IAT sensor, i.e. what is the highest reading, what is the lowest reading. I could put it in my freezer and measure it for 30deg and in my oven for 180degrees.

I’m looking for some input from the motor heads here, what do ya think?

mzmtg

iTrader: (11)

I think you may be on the right track as far as the function of the sensor. However, I dont think that the "cold air" fuel and timing curves would be very effective without the cold air. Just advancing the timing and richening the fuel overall doesnt always equal more horsepower.

sx7r

iTrader: (15)

if that's the case, then forget messing with the voltage...we could just stick the sensor in a little bag of ice.

MardiGrasMax

iTrader: (14)

Yep, this may or may not give more power. If it just effects timing we are in buisness. If its fuel and timing you will have to lean it out with an AFC or adjustable FPR.

Autobahn Max

I don't think the sensor mod would do that much good. It's a matter of density altitude; that being there is more good (dense) air for your engine to use at a cooler temperature.

One of my hobbies is flying little airplanes, and let me tell you, the performance of a little 110 horsepower Cessna 152 on a cool day is a hell of a lot better than on a hot day due to denser air. I'm sure the sensor on the Maxima helps a little but nothing major. The Max is fun for pushing you back in the seat, but pulling a 2 or 3 "G" turn in an airplane is a real kick!!!

Back to the subject...your engine runs better at cooler temperatures because more dense air is available. Can't change that with a sensor, but a turbo or supercharger will help....

MardiGrasMax

iTrader: (14)

But regardless of the cold air, if you can trick the ECU to give a little more timing, +4deg is all i think you would need, that would "probably" help the power levels. I realize that it might not work. But for $10 at radio shack it's worth a try.

[Edited by MardiGrasMax on 12-09-2000 at 01:37 PM]

Keven97SE

Won't work, sorry. Per the Nissan Maxima Factory Service Manual, the IAT sensor is used only for diagnostic purposes...that is, it's only used to provide feedback to the ECU, but the ECU does not use the signal to control any engine tuning.

FYI the MAF sensor provides "one stop shopping" for the ECU to gauge air flow...it directly measures the MASS of the incoming air, thus takes into account changes in air temperature. It's not volumetric flow rate measurement, which would require measurement of the ait temp to calculate the actual mass. Like I said, MAF does it all, that's the beauty of it.

MardiGrasMax

iTrader: (14)

DAM!

Thanks Keven

Woa, so does that mean that an AFC that adjusts the MAF voltage have an effect on timing as well?

jordandalley

I tried this. I put my IAT sensor in the freezer and measured the resistance. I went to a local electronics store and purchased a 10k ohm resistor (matching temperatures of -10) and it made absolutely no difference what so ever to my performance. The IAT imho does absolutely nothing. In fact, I have owned two Nissan Cefiro's with VQ30DE's and none of them came with IAT's.... it seems to be a Maxima thing.

NmexMAX

iTrader: (22)

Holy mother of old threads!!111