It consists of a centrifugal electric gas pump driven by a single-phase motor and operates at a throughput of up to 50 litres per minute while the pressure remains at only 0.1 bar (approx). Its thermal resistance is increased by innovative active cooling technology used on the electronic components. This ensures that the pump can withstand the harsh conditions in the engine compartment, meaning that ambient temperatures ranging from -10 degrees to +105 degrees are no problem for this equipment. It is also fitted with an integrated pressure sensor, which informs the vehicle control unit of the system pressure.
Operating the ACF pump
Harmful gases comprising volatile hydrocarbons form in the fuel tank. To prevent these from being released into the environment, the fuel vapours are trapped in an activated carbon filter (ACF) by the fuel tank ventilation system. The fuel tank ventilation system also ventilates the fuel tank so that no vacuums or excess pressure is created in the fuel tank as a result of the fuel being removed, during refuelling or due to changes in the outside temperature.
Since the storage capacity of the activated carbon filter is limited, it must be “regenerated” regularly to avoid saturation. In operating states where the engine and the combustion process can tolerate the additional amount of fuel, the fuel vapours from the activated carbon filter are mixed back into the intake air. For this purpose, the fuel vapours are drawn out of the activated carbon filter by means of the ACF pump and fed into the combustion process in a controlled manner via the purge valve. To prevent a vacuum from forming in the activated carbon filter during regeneration, it is ventilated via the venting valve which is then open. The activated carbon filter is then purged with the fresh air supplied.
In the past, the vacuum in the intake manifold was sufficient to draw the fuel vapours into the engine and fresh air into the activated carbon filter at the same time. In modern engine generations, however, there is hardly any vacuum in the intake manifold. Environmental regulations also limit the time window during which the filter can be regenerated. Therefore, in this case, the ACF pump is used for active regeneration of the activated carbon filter.