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…will become Porsche's panacea in boosting performance but slashing emissions.
Rumoured to become standard on the new 911 range - which goes public at September's Frankfurt motor show - the KERS (Kinetic Energy Recovery System) device captures energy from braking and stores it in a flywheel. It is then available to "top up" engine power when needed.
The flywheel, which is about 100mm wide, will sit between the engine and the gearbox. It's size is equal to reports that the new 911 - coded the 991 - will have a wheelbase 100mm longer than the current 997 model.
The KERS will also assist in moving weight distribution closer to the centre of the car, a bonus for the rear-engined 911.
A KERS device was fitted to Porsche's concept 918 racer, the RSR Hybrid, but was used to charge batteries for electric motors. It was also used in an earlier 911 GT3 R Hybrid. Porsche test driver Walter Rohrl, interviewed by Carsguide earlier this year, says the KERS system provided "fantastic" acceleration but was "extremely noisy". That device was fitted in the position normally allocated for the passenger seat and was in a bare-metal shell racer. Putting it away from the cabin should eradicate potential noise issues. Porsche will launch the 991, at least in the less expensive versions, with a smaller-displacement engine. But the new 3.4-litre - down from 3.6-litre - is still expected to have a similar 254kW/390Nm output and yet faster acceleration.
Though bigger - it's expected to be about 70mm longer - the new 991 will be lighter than the current 997 thanks to an expanded inventory of alloy panels and mechanical components.
KERS is an energy recuperation system that takes energy from braking and moves it to electrical or mechanical storage systems. The Porsche system for its 991 is expected to be a mechanical-hydraulic system where the pressure of the braking is transmitted by fluid to the flywheel.
KERS was used by some Formula One teams in 2009. It was promptly banned by the FIA for the 2010 season as an "unfair advantage" but is now allowed for the 2011 season.
The mechanical version takes energy from braking and transmits that to a small flywheel that spins up to 80,000rpm. When extra power is needed - by pressing a button on the dashboard - the flywheel is connected by a clutch to the drivetrain.
It adds a reserve of power - topped up every time the car brakes - that can reduce demands on the engine, lowering fuel and emissions and giving additional performance to smaller-capacity engines. Additional weight of the flywheel is about 35kg.
Formula One cars are limited to a maximum KERS output of 60kW for up to 6.67 seconds per lap. F1 teams say KERS can reduce lap times between 0.1 seconds and 0.4 seconds a lap.
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