MAF Scaling Fundamentals

Hi to all members of the community.

I am new to the tuning world, so firstly I am sorry of any misunderstanding question.

In the course Practical Reflash Tuning there are several references to MAF Scaling Map.

In this map we have the frequency vs mass_air_flow, so the ECU knows how much air is taken in every engine rpm.

By looking histogram differences in the VCM Scanner and multiplying the differential-percentages to that map, I have the feeling we are fooling the ECU about how much air is taking in order to have near to 0% air-fuel corrections.

So for example, if in some point previously mass_air_flow was 20g/s and the trim correction was +1% we go to this point and multiply by 0.99, so after the change, it will be 19.8g/s. After that, the fuel is going to be affected in order to keep the same air-fuel ratio.

So if the air-fuel ratio, for example, is 14:1 the mass_fuel_flow will be 1.42g/s.

After multiplying air with 0.99 also fuel will be affected and it will become 1.41g/s.

So why we are calibrating the MAF Scaling to affect the fuel while the mass_air_flow should be linear due to the diameter & frequency of the intake-engine-rpm based on the mathematical type and we didn't go directly to AFR Table? I suppose we must change MAF calibration when we change the air intake system only right and do not change this while running on stock.

Did I have understood it correctly?

We aren't actually fooling the ECU by changing the MAF scaling. Instead what we're doing is correcting the scaling. While the MAF calibration should be very accurate in a stock engine, we find that any changes we make to the intake system can affect the calibration and hence the numbers are no longer correct. Provided the injector data is correct, when the MAF is reporting the true airflow into the engine, the AFR will match the target.