The hopes of one of sportscars' iconic marques rest on the new 919 Hybrid. CRAIG SCARBOROUGH takes a look at the technology behind the new Porsche
Porsche's decision to return to Le Mans and the premier LMP1 category has resulted in the new 919.
Externally a contemporary LMP1 design, albeit built to the new narrower-chassis rules, the 919 exhibits innovation mainly in its powertrain, with approximately 75Obhp coming from a tiny V4 turbo engine and two energy recovery systems (ERS). One of those is a unique exhaust-driven generator that charges the car's central battery.
The exhaust outlet is off-centre, exiting on one side of the dorsal fin on the engine cover. This is due to the complex exhaust routing feeding both the generator and turbo. Beceause clever exhaust-blown floor solutions are banned this year, this is a simple way to dump the exhaust gases, and the asymmetric set-up probably has little aero effect.
A unique means of recovering energy from the petrol engine is the exhaust-driven generator, which can create AC power to be sent via the power-control electronics for converting to DC power for storage in the battery.
The exhaust pipes split to feed both the turbocharger and the turbo-hybrid generator. On the end of the generator is a turbine, and the energy from the exhaust gases spins the turbine and thus the generator. The exhaust outlet from the generator joins that of the turbocharger to exit off-centre from the back of the car.
Notionally similar to F1's ERS-H, this system does not provide for the stored energy to be fed back into the generator to provide an exhaust flow when off throttle, as energy flows purely one way from the generator to the battery.
V4 PETROL ENGINE
As the WEC continues to downsize engines and upscale energy-recovery systems, the 919 is fitted with a two-litre V4 petrol engine.
Increasing its efficiency is a single turbocharger and direct injection, allowing the engine to produce around 5OObhp.
AV4is structurally more efficient than a straight four, meaning the engine can be fully stressed, being bolted between the monocoque and gearbox without external supports.
As energy-recovery systems add weight, any opportunity is taken to reduce weight around the car. For the gearbox, this means the seven-speed semi-automatic cluster is mounted inside a carbonfibre gear casing with titanium inserts around the highly stressed areas.
Similar to F1, but in contrast to Porsche's competitors Audi and Toyota, the battery system uses lithium-ion cells.
These are protected within a housing and sit in the passenger side of the cockpit. Energy recovered from both the front MGU and the turbo generator is stored within the battery, and all the power is released through the front-wheel-drive MGU.
A motor generator unit (MGU) is linked with driveshafts to the front wheels. Under braking this will act as a generator to harvest energy and store the power in the hybrid system's battery. Under acceleration, power from the battery will be redirected to power the MGU's motor. In this mode the car becomes four-wheel drive and the MGU will provide an estimated extra 250bhp.