In EFI systems, which sensor directly measures incoming air mass?

In EFI systems, which sensor directly measures incoming air mass?

• A. MAF sensor directly measures incoming air mass.
• B. MAP sensor directly measures mass.
• C. Oxygen sensor directly measures air mass.
• D. Ambient pressure sensor directly measures air mass.

Answer: (A)

The main idea is that fuel timing in EFI relies on knowing how much air actually enters the engine, not just how much air might be in the intake. The MAF sensor directly measures the mass flow of incoming air. It uses a sensing element (hot wire or hot film) placed in the airstream; the air cools the element, and the amount of cooling is proportional to how much air mass passes by. The ECU converts that cooling signal into a mass air flow rate (usually in grams per second), which it then uses to calculate the correct amount of fuel to inject. MAP, or manifold absolute pressure, senses the pressure inside the intake manifold. From that pressure, engine speed, and air temperature, the ECU can infer air density and estimate mass, but it’s not a direct measure of mass flow. Oxygen sensors read the exhaust’s oxygen content to adjust fueling but don’t tell you how much air is entering. Ambient pressure sensors track outside pressure, not the air mass entering the engine.

The main idea is that fuel timing in EFI relies on knowing how much air actually enters the engine, not just how much air might be in the intake. The MAF sensor directly measures the mass flow of incoming air. It uses a sensing element (hot wire or hot film) placed in the airstream; the air cools the element, and the amount of cooling is proportional to how much air mass passes by. The ECU converts that cooling signal into a mass air flow rate (usually in grams per second), which it then uses to calculate the correct amount of fuel to inject.

MAP, or manifold absolute pressure, senses the pressure inside the intake manifold. From that pressure, engine speed, and air temperature, the ECU can infer air density and estimate mass, but it’s not a direct measure of mass flow. Oxygen sensors read the exhaust’s oxygen content to adjust fueling but don’t tell you how much air is entering. Ambient pressure sensors track outside pressure, not the air mass entering the engine.