Variable-drive supercharger

By: Nicol Louw

The current trend of engine downsizing to lower fuel consumption and emissions relies mostly on the use of direct injection and turbocharging in petrol engines. Supercharging has lost favour compared with turbocharging, as the latter is more efficient owing to this technology utilising otherwise wasted exhaust energy (versus the supercharger sapping shaft power directly from the engine). Rotrak is of the opinion that supercharging combined with a variable drive has its place in downsized powertrains because small engines with a minimal cylinder count find it harder to supply the turbo with enough energy to achieve boost at low engine speeds. This hampers low-speed torque and response to driver demands. By using a centrifugal compressor that is connected via a variable drive to the crank of the engine, immediate torque response can be achieved giving the driver a large-engine feel while slashing CO2 emissions. The technology is currently being tested in a B-segment donor vehicle on a rolling dynamometer to measure performance. The results so far have been promising and the technology will be shown to interested parties once the control algorithms are fully developed.

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