How manifold temperature affects intake air temperature?

 

I have made significant changes after the last intake study. Main change is the location of the intake air temp sensor.

Recommendation from Autronic is to have the IAT sensor as close as possible to throttle blades. In my case sensor is located about 10mm from the throttle blade

Reasoning is that this way sensor can read the real temperature of the air entering the engine.

 

For the tests, I added additional sensors to measure different temperatures. Sensor location and type is as follows:

Intake Air Temp: Intake air temperature measured by original SM4 IAT sensor.

Intake Air Temp 2: Intake air temperature measured with K-type wire thermocoupler. Sensor is located in stock Carbon fiber IAT sensor location.

Intake Manif: Manifold temperature measured with K-Type wire thermocoupler bonded to intake manifold.

 

Picture above shows all sensors described above and shows my drive from work to home, This graph shows several things:

1. Sensor location. Autronic theory is right, compare orange line and red one. Orange is the temp from Autronic sensor close to throttles compared to red line which is measured from the carbon fiber intake. For example, around 700 sec, sensor temp closer to throttle changes about 5 degrees, while the other sensor further from throttles doesn't change at all.

2. Autronic sensor is very good and fast. K-type thermocoupler is generally very fast to react, but Autronic sensor is almost as good.

3. How much manifold temperature affects the intake air temperature. This proves that Autronic theory is right again.

Next graph, let's see how speed affects the manifold temperature?

Graph above shows how speed affects the manifold temperature. As expected, manifold temperature changes when car speed changes.

Manifold temperature is quite high and has a big effect to heat soak.

In normal M3 AFM, sensor is located inside the AFM and temperature change should be similar to the red line.

In stock installation, leave the sensor where it is since ECU is tuned for that location.