Electronic Solutions for Motorsport

Clamp MAF Signal – Why do it?

2 min read

The MoviChip ATF lets you clamp your MAF voltage. You can clamp the maximum voltage and/or clamp the minimum voltage that the car’s ECU will ever see, but why would you clamp the MAF signal?

Clamp MAF Signal Voltage – Two reasons

1.Your cars ECU will not accept a voltage over 4.5 volt for example. the MoviChip ATF will output up to 5 volts to the engine ECU but you can set the maximum voltage between 4 & 5 volts depending on what your engine’s ECU needs (obviously you need to be sure your AFRs are correct with the clamped voltage)

2.Many reasons to clamp the minimum voltage but unstable idle is probably the most obvious. If you have made changes to your cams and/or intake, it is possible that airflow through your MAF sensor at idle is no longer stable ie there is reversion through the MAF sensor which is causing it to send unstable voltages or even zero volt signals to the engine ECU causing super lumpy idle and maybe even stalling. By setting a floor on the minimum voltage that the engine’s ECU sees, the idle can be made more stable and the chance of stalling reduced.

How to set up the MAF clamp voltage?

In the MoviChip ATF App, go to the MAF menu

Set the MAX MAF voltage to what you need

For minimum MAF voltage, monitor the MAF signal ie “MAF Actual” percentage at idle and choose the lowest percentage that you want the engine’s ECU to receive.

Set MAF Lock to YES and the MAF signal voltages are now clamped.

IMPORTANT: If you are using the auto tune feature you need to be sure that the engine can achieve the AFR targets you have set, within the range of voltages you have chosen in the MAF Lock settings, otherwise the autotune function will be trying to achieve an AFR that is not possible because of the limits set in the MAF Lock settings. This will cause all sorts of running issues.


I only want to clamp the MAX MAF signal voltage

Just set the minimum voltage to the lowest possible setting

I only want to clamp the idle MAF signal voltage

Just set the maximum voltage to 5 volts

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