Air Temp Relocation Kit

[Marc Haibeck]

My strategy for the inlet air temperature sensor is to improve its operation when the air temperature is rapidly changing. Especially in a drag racing situation.

I have not observed the fuel trim changing significantly with respect to engine inlet temperature. At light engine loads the oxygen sensors have great authority over the AFR. They set the AFR.

At a stop light or at the starting line at the track the sensor in the OE location is measuring the temperature of the plenum. Maybe 150 degrees F. When the car starts moving, by 20 mph or so the plenum is flooded with ambient temperature air. Maybe at 75 degrees F on a nice summer day. The air is going so fast that it picks up little heat from the plenum. The air going into the cylinder heads is nearly at ambient temperature. Meanwhile the air temperature reported by the sensor is only a few degrees below the 150 degree plenum temperature by the time the car gets to 20 mph. Mounting the sensor in an area that corresponds to the temperature of the air going into the engine provides a more accurate engine inlet temperature when the air flow is rapidly increasing. With the sensor in the OE location it can be observed that the air inlet temperature being reported to the ECM is at about 120 degrees when the car is halfway through the quarter mile going 70 mph. At the same time the engine is consuming air nearly at the ambient temperature.

The OE calibration retards the spark 3 degrees when the inlet air sensor is reading 150 degrees F. This is a horrible way to start a drag race. With a relocated sensor I retard the spark 1 degree at 90 degrees F. I figure that if the ambient temperature is 90 degrees or more you are probably not looking to set a new personal record that day and it's better to protect the engine from detonation.