Electronic fuel injection control in modern automotive engines: Is the following statement accurate—‘‘In a fuel-injection system, the Electronic Control Module (ECM) computes the optimum fuel-injection volume for the current engine condition from sensor data, and then injects that volume into the intake manifold at the optimum timing’’?

Introduction / Context:

Electronic fuel injection replaced carburetors by metering fuel precisely according to engine operating conditions. The Electronic Control Module (ECM), also called the Engine Control Unit (ECU), reads multiple sensors and commands injectors to deliver an amount of fuel that achieves the target air–fuel ratio while meeting power, emissions, and drivability goals. The statement claims the ECM calculates the optimum injection quantity and schedules it at the appropriate time into the intake manifold—this describes manifold/port fuel injection behavior.

Given Data / Assumptions:

• Multi-point or single-point port fuel injection (PFI/MPI) with injectors spraying into the intake manifold runners.
• Standard automotive sensors: Mass Air Flow (MAF) or Manifold Absolute Pressure (MAP), Throttle Position, Engine Coolant Temperature, Intake Air Temperature, Oxygen/Lambda sensor, Crank/Cam position, etc.
• Closed-loop feedback during part-load and open-loop maps at cold start/WOT.

Concept / Approach:

The ECM estimates intake air mass (air-charge) and computes required fuel mass using a target λ (lambda). It then converts fuel mass to injector pulse width, compensating for battery voltage, fuel pressure, injector dead-time, wall-wetting, and temperature. Timing of injection is synchronized to crank/cam signals so fuel arrives before intake-valve opening for good vaporization and mixture preparation.

Step-by-Step Solution:

Verification / Alternative check:

Closed-loop corrections from the oxygen sensor trim the base calculation to maintain stoichiometry (≈14.7:1 for gasoline) at cruise; during transients the ECM uses acceleration enrichment and wall-film models. All align with the statement.

Why Other Options Are Wrong:

• Incorrect / fixed volume: modern ECUs continuously calculate and adjust fueling.
• Only DI: direct injection sprays into the cylinder; the statement explicitly references injection into the intake manifold—PFI, not DI.
• Only at WOT: computation occurs under all loads and modes.

Common Pitfalls:

• Confusing PFI (manifold injection) with DI (in-cylinder injection).
• Overlooking compensation tables that refine the base pulse width.

Final Answer:

Correct