Load changes
During rapid load increases, the mg air/combustion increases quickly and it is well known that a petrol engine then requires a richer mixture. This is because the pressure increase in the intake manifold results in fuel being deposited on the walls, the so-called wet film increases. The fuel quantity that is lost here must be replaced by a slightly greater injection quantity, which is achieved by increasing the correction factor by a few percentage points. For example, the correction factor can be increased from 1.00 to 1.03, which gives a 3% increase in the fuel quantity.
As soon as the load increase ceases, the correction factor will return to its original value.
During a load decrease, the function is the opposite. The wet film deposited on the walls of the intake manifold quickly vaporize as the pressure drops. The injected quantity of fuel must then be reduced so that emissions and fuel economy do not deteriorate. This is achieved by reducing the correction factor by a few percentage points. For example, the correction factor can be reduced from 1.00 to 0.96, which gives a 4% reduction in the fuel quantity.
Closed loop is deactivated during load changes (if it was active) when the engine coolant temperature is below 40°C. This is because closed loop would otherwise counter-compensate. When the engine coolant temperature exceeds 70°C, closed loop will stay active during load changes, as fuel correction is then so small that counter-compensation will not affect the running of the engine. The amount with which the correction factor is changed from 1.00 during load changes depends on how fast the air mass/combustion changes and on the engine coolant temperature.
The described function corresponds to the accelerator pump or damper piston on cars with carburetor engines.