Why must fuel quantity be adjusted automatically in fuel metering systems?

Fuel quantity must be adjusted automatically in fuel metering systems primarily to correct for changes in ambient temperature or pressure. This adjustment is crucial because variations in temperature and pressure can significantly impact the density of the fuel, which in turn affects the amount of fuel being delivered to the engine.

As temperature increases, fuel expands and becomes less dense, while a drop in temperature causes it to contract and become denser. Similarly, changes in atmospheric pressure can influence how fuel is delivered, as lower pressure can reduce fuel flow rates.

By automatically adjusting fuel quantity based on these environmental conditions, the fuel metering system optimizes performance and maintains the desired air-fuel ratio necessary for efficient combustion. This ensures that the engine operates effectively under different operating conditions, mitigating potential issues such as misfiring, power loss, or increased emissions.