Load changes

A sudden load increase causes the mg air/combustion to increase rapidly and it is well known that petrol engines then require a richer mixture. This is because fuel is deposited on the walls of the intake manifold due to the increase in pressure there, and the wet-film thickness increases. The fuel quantity used here must be replaced by a slightly larger quantity of injected fuel, 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 3% more fuel.

As soon as the load increase stops, the correction factor returns to its original value.

In the case of a load reduction, the function is reversed. The wet-film deposited on the walls of the inlet manifold thins quickly as the pressure drops. The quantity of injected fuel must then be reduced to avoid a negative effect on emissions and fuel consumption, so the correction factor is reduced by a few percentage points. For example, the correction factor can be reduced from 1.00 to 0.96, giving a 4% reduction in fuel quantity.

When the engine coolant temperature is below 40C, the closed loop will be disabled during load changes (if it was active). The reason for this is that the closed loop would otherwise compensate. When the engine coolant temperature exceeds 70C, the closed loop will be active during load changes, as the fuel correction is then so small that the compensation would not affect the running of the engine. The amount that the correction factor is moved from 1.00 in connection with load changes depends on how fast the air mass/combustion changes and on the engine coolant temperature.

On a car with a carburetor engine, the function described above corresponds to the accelerator pump or damper piston.