The air Intake temperature sensor works on the same principle as the coolant sensor. It is located in the intake manifold so it can measure the intake air temperature. The IAT is a thermistor, a semi-conductive material that changes resistance in relation to its temperature. There are two types of thermistors, Negative Temperature Coefficient (NTC) and Positive Temperature Coefficient (PTC). A NTC thermistor’s resistance decreases as temperature rises, while a PTC thermistor’s resistance increases as temperature rises. Most thermistors, including the AIT, work on the NTC principle. Thus a low air intake temperature produces a high resistance, and a high temperature produces a low resistance.
The ECU supplies a steady reference voltage to one side of the thermistor. The ECU then reads the voltage drop between the sensor and a resistor to ground. The voltage reading is high when the intake air temperature is cold. This is because the AIT sensor resistance is high and most of the voltage will drop across the sensor. The voltage reading is low when the air intake temperature is hot. This is because the AIT sensor’s resistance is low and only a small amount of the voltage will drop across the resistor.
The ECU uses this information to help determine idle fuel mixture & air fuel ratio.
Basically, You can probably go to radio shack, get a resistor that will regulate the resistance in the circuit (ohms), with a dial, and then you can just dial in the equivalent temp to Ohm. Very simple device. There's only 2 wires leading to the AIT sensor, voltage in and voltage out. You could use a volt meter to determine which is which. then connect to the voltage out side with your tunable resistor.
I'm going to try it (resistor) out this week. relocating my AIT to the outside air, as I did, has given me a nice HP increase, however MPG went south, and my idle gets screwed up sometimes.
Matt Y2K-HEMI
'00 RC 4.7L 5spd
14.23 @ 94.49
Hopefully I explained this correct, I'm sure Bernd will pipe up and correct it.
In a message dated Wed, 4 Apr 2001 1:55:18 AM Eastern Daylight Time, Aajaynefour@cs.com writes:
<< I believe this topic was discussed about a week ago, but the results seemed
inconclusive. The IAT, as I understand it, is a variable resistor that
responds to temperature changes in the intake air stream and sends a voltage
to the PCM that is used to select the "optimal" air fuel ratio. So far so
good. Bernd has developed a simple but effective way of sending a "false"
voltage to the PCM making it think that the air is cooler than it actually is
and thereby selecting a different (richer ? - more performance biased) fuel
curve. Still good. My questions are as follows: Does the IAT in the stock
location react to air temperature changes to maintain a stoichiometric air
fuel ratio? If so, then basically Bernds IAT adjuster causes the PCM to
deviate from stoichiometric in the direction of a richer mixture as the air
temperature and therefore density stays the same. Wouldn't it be better to
place the IAT in a location where it could respond to cooler and denser air
or is there "room" to richen the mixture even if the air is relatively warm
and not as dense as it could be.
I don't doubt the effectiveness of this device, I am only trying to achieve a
better understanding of how this hot rodders trick works. If I am mistaken
in my understanding please correct me. I want to learn.
Thanks
Andrew
>>
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