I am planning on making my normally aspirated engine into a boosted Supercharged Engine using the AEM F/IC 6. From many searches and forum posts I've heard I need to do MAF (Mass Airflow Sensor) Clamping, I don't mind doing it however, I was to understand why it's so important and the major difference between a boosted application and normally aspirated... is it simply that a boosted application will draw in more air causing the MAF to read higher than usual? How can MAF see boost? (Small Reference https://www.youtube.com/watch?v=4sECmiN7EwA)

2 Answers 2


The MAF is a very accurate flow meter that sits in the intake air path. Its job is to tell the engine how much air is being drawn into the engine, so it can inject the correct amount of fuel to keep fuel/air mix at stochiometric, both so performance is at peak and smog is at minimums. These things are allied causes, so normally this thing is your friend and there's no reason to screw with it.

However, when you boost an engine that was never designed to be boosted, you introduce an array of problems. Among them is that the MAF is now indicating airflow numbers that are higher than expected because of so much air moving. To detect broken sensors, the engine PCM checks throttle, temperature, baro and MAF against each other, and will blow a code if a sensor "doesn't make any sense".

If the manufacturer sells a supercharged version of that car, they set upper limits in the PCM so it doesn't consider "being boosted" to be a sensor error. On a dedicated, built-for-purpose racing vehicle, you simply use a PCM that understands it may be boosted.

But of course the problem comes when you boost a made-for-street, EPA certified vehicle where the manufacturer never dreamed it would be boosted, and didn't give the PCM flexible enough parameters.

This vendor's hackaround to that is to trick the PCM and then take control of fuel injection.


The bottom line is, the MAF doesn't see boost, it sees air flow. The Manifold Absolute Pressure (MAP) sensor can see boost. In most normally aspirated cars, the MAF (if even equipped) and MAP work together along with other sensors to come up with the correct amount of fuel to be injected into the engine. Naturally aspirated engines only require a MAP sensor which can read pressures up to 1 bar (or a single atmosphere), while in boosted applications a MAP sensor which is capable of reading above 1 bar is needed so the computer can understand what is going on.

When I stated if a MAF is even equipped in a car, the ECU doesn't necessarily need a MAF in order to run correctly. There are two modes which an ECU could run an engine in. The first using the MAF. The second is called speed density. Speed density only uses a MAP without a MAF. While a MAF can do a great job at determining how much air is entering the engine, there is a point where boosted airflow becomes an issue and the MAF no longer can read the amount of air coming into the system. Think of it as the MAF "being pegged" or maxxed out. It would only be sending the maximum reading to the ECU and nothing more.

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