The Mass Air Flow (MAF) sensor is a device used in electronic fuel injection systems to directly measure the mass of air entering the engine.

Operating Principles#

There are two primary methods by which MAF sensors measure airflow:

• Flapper-Valve (Vane Air Flow): Uses a mechanical flap that is physically deflected by the incoming airflow. The degree of deflection corresponds to the air mass.
• Hot-Wire/Film Element: Uses a heated wire element in the airflow stream. As air flows over the element, it cools it down; the ECU measures the change in resistance required to keep the wire at a constant temperature, correlating this to the mass of the air.

Comparison to MAP Sensors#

Honda's PGM-FI systems primarily utilize MAP (Manifold Absolute Pressure) based speed-density systems.

• MAF System: Directly measures the air mass.
• MAP/Speed-Density System: Calculates air mass based on manifold pressure, air temperature, and engine RPM.

While MAF systems are excellent for direct measurement, Honda's MAP-based systems offer significant flexibility for performance tuning, as they are not restricted by the physical size or flow capacity of a MAF sensor housing.