Electric Superchargers a Boost to High Power Small Engines

Turbocharging and supercharging have long been used to get big engine performance from smaller, more fuel efficient engines. Both achieve this through better ‘breathing,’ that is, forcing more air at higher than ambient air pressure into the combustion chambers, thus providing extra oxygen that promotes more powerful combustion. The result is greater power compared a conventional engine

A turbocharger is driven by engine exhaust gases, while a supercharger is mechanically driven by the engine’s crankshaft via a belt, gears, shaft, or chain. Now there’s a more efficient type of supercharger driven by electricity. An example is the electric powered supercharger, or Variable Torque Enhancement System (VTES), from Britain’s Controlled Power Technologies.

A big advantage of an electric supercharger is that it can operate independent of engine speed, a key difference that makes it well suited for maintaining transient performance and drivability in downsized engines. This means instant torque response when you stomp on the throttle, since the electric supercharger significantly increases air charge density over the critical first 10 combustion cycles of a low speed transient.

Fitted with a low inertia compressor, the supercharger accelerates from idle to its maximum speed of 70,000 rpm in less than a third of a second, enabling an engine to achieve full load torque within one second at very low engine speeds. This fast dynamic response and rapid air boosting enables the system to react instantly to high transient load conditions, delivering up an additional 33 horsepower.

Combining the highly responsive electric supercharger in series with a conventional turbocharger makes it relatively easy to optimize engine response compared to other air charging methods. The VTES technology can also help reduce soot and particulate emissions from diesel engines, particularly when accelerating at low engine rpms. This could decrease the size and cost of diesel particulate filters since there are fewer particulates to deal with.

When installed in a 1.2-liter engine, VTES has been shown to deliver over a 50 percent increase in torque at engine speeds below 3,000 rpm, with more than 90 per cent of the available torque delivered in less than a second. Compared to a 1.6-liter naturally aspirated engine, a downsized engine with an electric supercharger can reduce 70-100 km/hr (44-63 mph) top gear acceleration time from 18 to 11 seconds.

An electric supercharger greatly reduces the expense and complexity involved in integrating supercharging technology into an existing engine design. The VTES was designed for use in a wide range of gasoline and diesel engine designs.

Electric superchargers could be a lower cost alternative to the electric motors integrated between the engine and transmission in parallel hybrid electric vehicles. Both provide additional torque for acceleration and hill climbing. Unlike the electric motor, however, an electric supercharger can operate with a vehicle’s existing 12 volt electrical system and does not require an expensive, advanced technology battery pack. Besides being less costly, it also provides easier packaging in front-wheel drive vehicles.

Power Technologies’ electric supercharger is already a key component in two development programs. It is being used in Ricardo’s HyBoost (Hybridized Boosted Optimized System with Turbo Compound) project. It is also used in a VW Passat-based demonstration program being conducted by independent engine developer AVL.