When it comes to downsizing engines for reduced fuel consumption and CO2 emissions the automotive research and development engineers at Antonov reckon a simple dual-speed mechanical approach is the optimum solution when considering supercharging.

“Two speeds are better than one,” says Chris Baylis operations director at Antonov Automotive Technologies based at Warwick in the UK.  “And two speeds are enough – particularly when considering the cost, weight, packaging and vehicle refinement implications for high volume car production.”

This was the key message from Baylis in a presentation delivered to motor industry experts attending a major automotive exposition taking place this week (6-8 May) at Stuttgart in Germany.  Held at the recently opened New Trade Fair Centre, Baylis addressed the subject at an open technology forum on supercharging and engine downsizing.

“Motorists have come to expect a certain level of performance from their vehicles,” said Baylis, “and while as an industry we strive for ever lower fuel consumption and CO2 emissions we have to keep driver expectations and vehicle performance in mind when making engines smaller.

“Car makers are increasingly looking at superchargers to enhance the performance of small engines.  Unlike turbochargers there are no heat issues to manage, and the study of exhaust gases can then be assigned to energy recovery systems.”

Using the dual-speed approach Antonov reckons that car makers could halve the size of the engine for any particular application with a dramatic reduction in fuel consumption and carbon emissions.

“A 25 to 50 per cent reduction in engine size seems feasible for road vehicles,” says Baylis. “The dual-speed supercharging solution certainly delivers the performance and, importantly for road cars, maintains excellent driveability.

“Improved fuel economy is fundamentally achieved through using a small displacement engine - with a dual-speed supercharger allowing it to run more often at low rpm.  The two speeds allow us to spread the charge of air from the supercharger to the engine over a wide engine speed range.

“Essentially we’re able to create a better match between the supercharger and its host engine – by running the supercharger faster at low engine speeds and slower at high engine speeds.  The benefit is predictable low speed engine torque that is always available for enhanced drivability and performance.  The change between drive ratios is smooth and virtually imperceptible to the driver.

“The ability of a dual-speed supercharger to operate as a passive device without the need for sophisticated and expensive electronic control systems or hydraulic actuators means low cost, high efficiency and simplicity of application.

“In addition, a supercharger with a simple dual-speed mechanical drive provides most of the benefit of a fully variable drive unit, or various complex combinations of supercharger and turbocharger, at a fraction of the cost,” adds Baylis.

Three dual-speed supercharger studies are currently being pursued by Antonov.  This includes an engine downsizing application for a typical family car, an aftermarket application already in production for high performance vehicles and a performance enhancement application for off-road vehicles with relatively poor class performance, which is also in production.