What data do modern metering systems primarily base fueling on?

• A. Engine oil temperature
• B. Intake manifold vacuum
• C. Air mass via MAF sensor and injector calibration
• D. Battery voltage

Answer: (C)

Modern metering bases fueling on the mass of air entering the engine. The ECU uses a MAF sensor to measure air mass flow and, together with known injector flow characteristics (injector calibration), calculates how much fuel to deliver each cycle to reach the target air–fuel ratio. This direct measure of air mass stays accurate across engine speeds, loads, and conditions, so the fuel amount can be precisely matched to the amount of air available for combustion.

Intake manifold vacuum data can indicate engine load, but that approach is more typical of older or alternative systems (MAP/volume-based methods) and isn’t the primary basis in most modern metering. Engine oil temperature mainly affects enrichment during cold starts or warm-up, not the core fueling calculation. Battery voltage can influence sensor readings and injector performance indirectly, but it isn’t the primary data used to determine the fuel amount. The injector calibration ensures the commanded fuel aligns with the measured air mass to achieve the correct mixture.