The Swedish manufacturer says that when combined with a turbocharged four-cylinder engine, the experimental system – known as Flywheel KERS (kinetic energy recovery system) – has the potential to reduce fuel consumption by up to 25 per cent compared with a six-cylinder engine of comparable power.
Volvo’s Flywheel KERS is fitted to the rear axle and harnesses otherwise-wasted braking energy, which causes the flywheel to spin at up to 60,000rpm. The combustion engine that drives the front wheels is switched off as soon as braking begins. When the car starts moving off again, the flywheel’s rotation is transferred to the rear wheels via a specially designed transmission.
When the energy in the flywheel is combined with the combustion engine’s full capacity, Volvo says it can give the car a momentary 60kW power boost, which, in the case of Volvo’s experimental S60 development car, translated to a 0-100km/h sprint of 5.5 seconds – two seconds quicker than the 177kW/320Nm turbocharged 2.0-litre four-cylinder Volvo S60 T5.
Volvo’s carbonfibre flywheel has a diameter of 200mm and weighs six kilograms, making it significantly lighter than conventional steel units.
Volvo powertrain engineering vice president Derek Crabb explained Volvo was the first manufacturer to apply flywheel technology to the rear axle of a car with a combustion engine driving the front wheels.
“The next step after completing these successful tests is to evaluate how the technology can be implemented in our upcoming car models,” Crabb said.
Volvo is expected to implement Flywheel KERS technology in its next-generation production cars, due later this decade.