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Automotive Engineer

Conti makes light work of electric vacuum pumps

Plastic module saves weight and CO2

Simon Bickerstaffe in Technology.

Tier One Continental has developed a lightweight, second-generation electric vacuum pump which can reduce tailpipe CO2 emissions by almost 2g/km.

Conventional vacuum pumps are gear- or belt-driven but this incurs a parasitic loss on the engine. And most hybrid powertrains eliminate the front-end accesory drive altogether so this is no longer available as a power take-off.

Conti's head of vacuum pump development, Michael Juerging, said: “An electric vacuum pump can eliminate between 1.4 and 1.8g/km CO2 compared to a mechanical vacuum pump. Since it does not rely on the engine, it can provide a vacuum even if the engine is switched off as part of a stop-start function.”

Vacuum pumps are required for all diesel engines because the unthrottled combustion process means that there is insufficient vacuum in the intake manifold to power the brake booster. Direct injection gasoline engines tend to need them for for the same reason. Powering them from the engine is inefficient because they consume energy even when the vacuum is not required. Hybrid and electric powertrains offer little or no option to power the pump mechanically.

Electric pumps are the solution, and providing vacuum on-demand makes them more efficient, but existing designs are relatively bulky and heavy. Conti's second-generation design replaces the cast aluminium body with a plastic injection moulding. This makes the pump smaller and around 500g lighter.

The pump is in series production and the first applications include electric vans and city cars in the North American and European markets.