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IAT Compensation table

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I used the HP recommended method re IAT compensation of 3% for every 10 degree either side of 20 degree celcius ( colder, +3% for every 10 dgree and hotter -3%)

I was then researching and came across suggestion o zeroing all IAT value , tune engine and make note of the temp then use whatever the temp was as your 0 point. I don't see how this approach would work as IAT temp will increase as engine heats up so one will be chasing his tail in my honest opinion as your fuel table will have no IAT correction initially and main fuel table will wrong once you apply IAT trim.

I think having IAT based on general values to deduct after 20 degree seems sensibale and thought I seek your opinion.

finally does link ecu have heat soat function, saw a table callled charged air temp which uses ect as reference than IAT depending on rpm and how one configures it. I can't see this option for my link. my iat is in the standard one in m52 which is inside of manifold and whilst at traffic, the temp goes really high

Yes the Link has charge temp approximation so you can tune the weight the coolant temp has on the charge temp based on conditions of your choosing.

Coolant temp is more of a factor at low airflow, and on engines with metal intake manifolds vs. plastic ones since the plastic doesn't heat soak as much.

0 correction at standard conditions makes more sense to me when VE tuning.

Zeroing correction at the conditions you're mainly operating during an initial tune wouldn't have the concern of skewing VE if you're tuning an old style injector on time system.

HPA tries to give starting point suggestions, and provide understanding and workflows that allow you to make your own adjustments until you get optimized results. How much you have to adjust IAT comp per 10 degrees will vary because ultimately you're trying to approximate the impact of not just the temperature where the IAT sensor is, but the intake tract, the intake port temp etc., because on many standalones this is your only temperature compensation for air mass.

Also keep in mind most "fast" IAT sensors are not that fast, and they often heat soak.

They are fast compared to a fluid temp sensor.

This is a data capture from a calibration test, what is shown is a step from 40 to 50 degrees over 1 minute in a temperature controlled environment.

Blue is a K-Type Thermocouple.

Red and Orange are a Delco Air Temp Sensor

Purple is a Bosch Fluid Temp sensor

Green is a Cylinder Head Temp sensor that was being tested.

Pizza Oven 40 to 50 by Stephen Dean, on Flickr

The Air Temps come up relatively quickly, the Fluid Temp sensor with the greater thermal mass (used as a analogue filter of the fluid) takes longer to respond to the initial change, and even more time to reach equilibrium with the other sensors and surrounding air temp. (it actually takes it around 15 minutes to stabilise)

Yup, it's certainly all relative.

Be mindful that the effective thermal mass density for coolant energy transfer to sensor will be a couple of thousand times that of air.

Putting a Thermocouple just after the thermostat can be interesting in seeing the temperature changes in the coolant, especially at the point that the coolant temperature is getting high enough to start to open the thermostat and induce cold water from the radiator.

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