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Intake sensor location

Heat soak is one of the typical problems with ECU’s and correcting the mixture based on intake and water temperatures is not easy.

To combat this problem, Autronic has a feature called Charge Temp table and is used to correct the mixture based on the intake air and water temperatures. Before going into details how it works, let’s talk about the location of the intake air sensor. Location should be the where it gives the best indication to the ECU what is the real temperature of the air entering the engine.

Below is a picture of my engine compartment. Possible locations for sensors are marked as 1 and 2.
1.    Carbon fiber snorkel.
2.    Intake manifold

Typically for OEM ECU’s some would fit the sensor to location 1, where the temperature is the coolest and that would potentially increase the power since ECU would inject more fuel.
Location 2 would be problematic since it might be too hot.

Sensor locations for the test were following:

Sensor 1. Carbon fiber air temp: about 40cm from the Autronic Air temp sensor and intake manifold.
Sensor 2. Manif internal intake air temp: K-type wire sensor inside the manifold, inserted from the vacuum port. 10cm from the intake valve, after throttle butterfly.
Sensor 3. Intake manif housing temp: K-type sensor bonded to the manifold. 5cm from the vacuum port
Sensor 4. Autronic intake air temp: Temperature measured by Autronic IAT sensor. 10mm before the throttle butterfly, on the opening side.
Green trace is the throttle position from Autronic.

Conclusions:

Orange trace, Sensor 1, Carbon fiber sensor is way too far and doesn't really react at all to throttle changes like other sensors. Even the manifold housing temperature gives an better indication of the intake air temperature.
Red trace, Sensor 2 is a K-type wire sensor and very fast as seen from the trace.
Blue trace, Sensor 4 is the Autronic sensor. Fast enough and gives a good indication to ECU what the temps really are.
So, it is pretty clear where to mount the sensor, Sensor location 1 is too far to give a good indication what the air temp really is.

Sensor is now installed to location 2, which gives the best indication to ECU what the real air temperature is. Now just make sure your charge temo is tuned correctly.