How do fuel temperature and density affect metering calculations?

• A. Denser fuel requires less volume to deliver the same mass; ECU may adjust flow using density compensation and rail pressure to maintain mass flow.
• B. Denser fuel requires more volume to deliver the same mass; ECU reduces fuel flow.
• C. Fuel temperature and density have no effect on metering calculations once the ECU compensates.
• D. Density only affects ignition timing, not metering.

Answer: (A)

Fuel metering targets delivering a specific fuel mass, not a fixed volume. Fuel density sets how much mass is in a given volume, and density varies with temperature. Denser fuel (higher density) has more mass per unit volume, so less volume is needed to deliver the same mass. The ECU accounts for this by density compensation and adjusting rail pressure to keep the desired mass flow—and thus the correct air-fuel ratio—steady. If the fuel is less dense (warmer fuel), you’d need more volume (or a longer injector pulse) to reach the same mass, and the ECU makes corresponding adjustments. So, temperature and density directly affect the volume your injectors must deliver for a given mass, and metering calculations are adjusted to maintain consistent mass flow.