This experiment is for the IAT sensor mod in which the signal from the IAT sensor is bypassed with a fixed value resistor. The value of the resistor is chosen such that the ECU reads a temperature hotter than the IAT sensor is reporting.
The theory: Fuel mix is determined by a very large number of factors and is directly controlled by the length of time the fuel injectors stay open. Each factor is supplied to the ECU through all the engine's sensors. The ECU then takes each value to a lookup table which will return a constant multiplier for a given input. For example, if a lean condition is detected from the oxygen sensor, the multiplier will be greater than 1, resulting in a richer mix next cycle. The same thing goes for the intake air temperature. If the sensor is reading a hot temperature (hotter than normal) then the lookup table for the IAT sensor will report a multiplier less than 1. By tricking the ECU into thinking it's always reading a very hot temperature from the intake, the ECU can be forced to reduce the length of the pulse controlling the fuel injector by manipulating one of the many factors controlling fuel mix.
I used the same resistors SVOBoy showed. The two 220 Ohm resistors measured 107.8 Ohms in parallel. This should produce a reading of approximately 240 to 250 degrees F. The coolant temp gauge read the same temp as before the mod. It does not appear that the leaning effects of this mod has enough effect to overheat the engine.
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<table border="5" cellpadding="5">
<tr>
<th colspan="2">
<b>10/5/05 - IAT Sensor Mod Trial #1</b>
</th>
</tr>
<tr>
<td>Fuel economy:</td>
<td>35.3 mpg</td>
</tr>
<tr>
<td>Previous fuel economy:</td>
<td>34.0 mpg</td>
</tr>
<tr>
<td>Percent difference:</td>
<td>+3.82%</td>
</tr>
<tr>
<td>Trip:</td>
<td>79.35 miles</td>
</tr>
<tr>
<td>Fuel used:</td>
<td>2.245 gallons</td>
</tr>
<tr>
<td>Fuel grade:</td>
<td>Shell V-Power 93 octane</td>
</tr>
<tr>
<td>Driving type:</td>
<td>Highway</td>
</tr>
<tr>
<td>Target speed:</td>
<td>65 mph</td>
</tr>
<tr>
<td>Tire pressure:</td>
<td>40 psi</td>
</tr>
<tr>
<td>Temperature:</td>
<td>79 degrees</td>
</tr>
</table>
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The previous fuel economy used was from Trial #4 of the tire pressure experiment. I'm averaging the temperatures for the trip there and back to get 79 degrees, which was tonight's temperature.
I don't know if I'll do any more trials because I really want to get started on acetone. It is possible that Honda uses different resistences for temperatures than other manufacturers. I'll try and research this to see if another trial is worthwhile.
Everyone else conducting this experiment, please post your results.
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