Porsche Hybrid Race Car is Faster than Formula One
The technical regulations from the FIA for the WEC and Le Mans successfully delivered close competition between the conceptually very different class 1 Le Mans hybrid prototypes entered by Audi, Porsche and Toyota. As a consequence this never allowed the question – what would be the potential of the Porsche 919 Hybrid if it wasn’t chained by the limitations – to be answered; until now.
Stephen Mitas, Chief Race Engineer LMP1, was heading the project: “It was kind of an engineer’s dream come true for us”, the Australian admits. “Having developed, improved and raced the car for four years, the guys had a very close relationship to it. We all knew, no matter how successful the 919 Hybrid was, it could never show its full abilities. Actually even the Evo version doesn’t fully exploit the technical potential. This time we were not limited by regulations but resources. It is a very satisfying feeling that what we’ve done to the car was enough to crack the Formula One record.”
To prepare the record car, the base was the 2017 world championship car. On top came developments that were prepared for the 2018 WEC but never raced after the end of 2017 withdrawal. Additionally, several aerodynamic modifications were made.
For the Porsche 919 Hybrid Evo the entire hardware of the power train remained untouched. The 919 is powered by a compact two-litre turbo charged V4-cylinder engine and two different energy recovery systems – brake energy from the front axle combined with exhaust energy. The combustion engine drives the rear axle while the electric motor boosts the front axle to accelerate the car with four-wheel drive. At the same time it recuperates energy from the exhaust system that otherwise would pass unused in to the atmosphere. The electrical energy that comes from the front brakes and the exhaust system is temporarily stored in a liquid-cooled lithium ion battery.
The WEC efficiency regulations limited the energy from fuel per lap by using a fuel flow meter. At the 2017 championship round in Spa, in the Porsche 919 Hybrid’s final season, it could use 1.784 kilogram/2.464 liters of fuel per lap. The V4 combustion engine’s output back then was around 500 HP. Freed from these restrictions, equipped with an updated software but running the regular race fuel (E20, containing 20 percent bio ethanol), the 919 Hybrid Evo delivers 720 HP.
The amount of energy from the two recovery systems that could be used in Spa 2017 was 6.37 megajoule. This was by far below the systems’ potential. On his record lap Neel Jani enjoyed a full boost of 8.49 megajoule – the e-machine’s output increased by ten per cent from 400 to 440 HP.
The engineers also unchained the aerodynamics of the 919 Evo from the regulations. The new larger front diffuser now balances the new and very large rear wing, both of which have actively controlled drag reduction systems. The hydraulically operated systems trim the trailing edge of the front diffuser and opens up the slot between the rear wing main plane and the flap respectively in order increase the aerodynamic efficiency of the Evo. Underneath the Evo the turning vanes and floor have been optimized with fixed height side skirts to increase the aerodynamic performance again as efficiently as possible. In total the aero modifications resulted in 53 per cent higher downforce and an increase in efficiency by 66 per cent (compared to the 2017 Spa WEC qualifying).