Volvo has completed extensive testing of kinetic flywheel KERS technology on public roads, which was fitted to the rear axle of an S60 with a four-cylinder turbo, giving the driver an extra 80 horsepower, while reducing fuel consumption by up to 25 percent compared with a six-cylinder turbo engine at a comparable performance level.

Under braking, the combustion engine is switched off and the braking energy causes the flywheel to spin at up to 60,000 revs per minute and when the car starts moving off again, the flywheel’s rotation is transferred to the rear wheels via a specially designed transmission.

Because the flywheel is activated by braking, and the duration of the energy storage/length of time the flywheel spins is limited, the technology is most effective in city driving, featuring repeated stops and starts.

The experimental S60 thanks to the extra 80 horsepower accelerates from 0-62mph in 5.5 seconds.

The Flywheel KERS system in the experimental system is made of carbon fibre and weighs about six kilograms and has a diameter of 20 centimetres.

“We are the first manufacturer that has applied flywheel technology to the rear axle of a car fitted 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,” concludes Derek Crabb, Vice President Powertrain Engineering at Volvo Car Group.