Throttling losses

Throttling losses are all pressure losses that occur in a system at throttling points. Throttle points are, for example, throttle flaps , valves , cross-sectional constrictions, rough surfaces or small deflection radii.

It is important to keep throttle losses as low as possible. In the development of internal combustion engines , efforts are made to reduce the throttle losses and thus the gas exchange work within the intake system , in that the load control is done by variable valve trains and not with a throttle valve.

Valve controls that reduce throttling losses are used by many manufacturers, but implemented and named differently. Honda calls its system VTEC , at Toyota it is called Valvematik, at Nissan Neo VVL, at Mitsubishi MIVEC, at Fiat Multiair, at BMW Valvetronic and at Porsche Variocam Plus. In all of the cases mentioned, it is used in combination with an additional adjustment of the valve timing to increase efficiency and performance.

Another technique for reducing throttle losses is cylinder deactivation, in which some of the cylinders are deactivated by switching off the ignition spark and the valve opening, so that the cylinders that are not deactivated can be operated with the throttle valve open with the same engine output. This technique is used e.g. B. used by the brands of the Volkswagen Group .