MAF CAL History – Development & Testing
April 29, 2026This article covers the history of MAF CAL, why MoviChip developed the product and how the product is tested.
Why Does MAF CAL Exist?
Over the years we have had engines where fuelling has not been where we wanted it to be.
SR20VE
Originally the product was designed for SR20VE engines running the standard SR20 ECU. In this setup, without MAF calibration the engine will run rich due to the SR20VE injectors being larger. MAF CAL (called ATF at the time) was developed to adjust the MAF signal to correct the fuelling.
In this case, MAF CAL was used to reduce the MAF signal going to the ECU. As has been covered elsewhere on this website, reducing MAF signal will usually increase ignition timing which can lead to catastrophic detonation if engine is not tuned properly.
In the case of the SR20VE, this engine runs more ignition timing than the SR20DE so two birds were killed with one stone. We gained ignition timing which we wanted and we reduced over-rich fuelling at lower loads.
The SR20 ECU is equipped with a narrowband lambda sensor. In this case there was no compensation coming from the engine ECU at high engine loads, this necessitated the use of an aftermarket wideband gauge to tune the MAF signal.
Mileage
MAF CAL has been used on this engine for over 100,000km.
1.8T
Development of MAF CAL continued with the VAG 1.8T 20V engine. The engine in question runs a larger turbo. With the increased engine power, the MAF sensor on the car was appearing to max out, specifically, the MAF signal was topping out at around 4.4 volts. It was also found that the engine ECU was targeting lambda 1 for most operating conditions which was not ideal.
To gain better air flow accuracy at higher loads and higher RPM, the 70mm MAF housing was replaced with an 80mm item (the actual Bosch MAF sensor was kept the same). The intake routing was also changed to put the MAF sensor in a straight pipe. With the original 70mm housing, MAF location was less then ideal as it was located immediately after a 45 degree and this was causing a very choppy MAF signal.
These changes gave a smoother MAF signal but meant fuel trims were “all over the shop”.
The original engine map had been heavily leaning on closed loop fuelling at idle to pull fuel. Fuel trims were -20% to -25%. With the larger MAF housing, idle fuelling corrections came right down to around -10% but fuelling above idle, was slightly lean and got leaner as RPM and load increased. In this case MAF CAL is used to slightly decrease the MAF signal around idle and gradually increase the MAF signal as load and RPM increases.
The result of these changes is a smoother and more controllable engine with improved fuel economy.
Constant Development – Some Examples
The intake on this engine is constantly being changed. Different sized air filters, intake piping diameter and passive, pre-compressor water injection has also been added. MAF CAL is used to adapt the MAF signal after these changes to keep fuel trims as close to zero as possible. In the case of this 1.8T, the factory engine ECU (ME7.5) is equipped with a wideband lambda sensor which ultimately dictates the air fuel ratio.
In the middle of April 2026 a new design of MAF housing with an even larger diameter was installed. This led to less stability in the MAF signal at idle. New firmware is included on orders made from 22.4.26 which improves MAF signal quality when airflow through the MAF sensor is unstable.
Mileage
MAF CAL has covered over 20,000km on this 1.8T and refinements continue.
Future Development
What’s next for MAF CAL?
λ 1.0
I mentioned above the current engine MAP in the engine is targeting 1 lambda most of the time, even under full boost. This led to the development of MAF CAL ADVANCE.
MAF CAL ADVANCE
MAF CAL ADVANCE is a development of MAF CAL. Whereas MAF CAL is designed to give the engine ECU an accurate picture of air entering the engine, and allow the engine ECU to achieve it’s target AFRs through the use of closed loop fuelling. MAF CAL ADVANCE is designed to allow the user to control the AFR target on wideband equipped engine ECUs. This is achieved by the engine ECU being disconnected from the wideband sensor. MAF CAL ADVANCE then uses the signal from a wideband controller to achieve the lambda targets set by the user in the MAF CAL ADVANCE app.
MAF CAL ADVANCE has not been released yet but more information will follow. If you want to receive updates on this product, subscribe to the MoviChip newsletter.
MAF Scaling/MAF Calibration with MAF CAL
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