Le Mans preview
After successfully unveiling and testing its new 919 Hybrid race car during the WEC prologue at the AutodromoNazionale di Monza, Porsche set forth its targets for the season. The Stuttgart based manufacturer is aiming to win the Le Mans 24-hours race (June 17/18), as well as the FIA World Endurance Championship titles for Manufacturers and Drivers respectively for the third year in a row.
To aid the team’s bid for success, the 2017 model of Porsche’s 919 Hybrid race car, which delivers a system output of around 900 hp (662 kW), was comprehensively reworked. The Le Mans prototype deploys a range of new innovations, particularly in relation to the vehicle’s aerodynamics, chassis, and the combustion engine.
The technical regulations for the 2017 FIA WEC World Endurance Championship introduce further limitations in terms of the dimensions of certain body components that affect aerodynamics. To increase safety, the new measurements reduce the downforce of the LMP1 prototypes, which in turn lowers the vehicle’s cornering speed for safety reasons.
Based on the new specifications and developmental findings, the Porsche engineers devised two brand-new aerodynamics packages for the 919 Hybrid – driven by a desire to compensate for the increased lap times resulting from the regulatory requirements. One of the new aerodynamics packages is specifically designed for the high-speed track at Le Mans. To achieve maximum top speeds on the extremely long straight sections, the package design focuses on minimising air resistance. The second aerodynamics package compensates for a higher level of drag with greater downforce for tracks with twists and turns.
As part of the package of enhancement measures, the Porsche engineers have boosted the efficiency and performance of the drivetrain. The transmission on the front and rear axle, the combustion engine, the electric motor and the energy recovery systems have all been optimised, with the basic principle behind the drive system unchanged. The rear axle of the 919 is still driven by an extremely compact two-litre V4 combustion engine, which combines downsizing turbo technology with efficient direct fuel injection to deliver just less than 500 hp (368 kW). Two different energy recovery systems – a braking energy recovery system on the front axle plus an exhaust energy recovery system – feed a lithium-ion battery, which in turn powers an electric motor capable of supplying additional power of over 400 hp (294 kW) to the front axle on demand.
The 919 Hybrid, developed in Weissach, is the only prototype to recover energy during acceleration as well as braking. It achieves a system power of more than 900 hp (662 kW), benefiting from the enormous traction generated when the car accelerates out of bends with a further 400 hp of power on the front axle, transforming the 919 into an all-wheel drive vehicle.
Approximately 60 per cent of the recovered energy comes from the KERS (Kinetic Energy Recovery System) on the front-axle brakes. The remaining 40 per cent is generated by the exhaust energy recovery system. An average of 80 per cent of the braking energy recovered from the front axle is immediately converted to drive energy. A further advantage of the highly efficient recuperation system is that it enables the 919 to perform with smaller and lighter brakes – a characteristic that not only reduces weight, but also air resistance, as smaller brakes require less cooling air.
To recover exhaust energy, a small turbine is fitted in the exhaust tract. This turbine runs at a speed of more than 120,000 rpm, powering a generator. Just like the energy recovered from the front brakes, the energy generated is stored in the lithium-ion battery until it is needed. The driver can access this stored energy on demand at the push of a button – using it to boost the car as it speeds out of a cornering manoeuvre while simultaneously replenishing the energy from the exhaust gas generated during acceleration. To ensure that the turbine functions just as efficiently at lower speeds, when exhaust pressure is low, the turbine features variable turbine geometry. In spite of the sophisticated technology on board, the engineering team was still able to achieve a weight reduction in the exhaust system.
The customer benefits – WEC is the ideal platform for technological pioneers with its unique efficiency regulations for Class 1 Le Mans prototypes (LMP1), the WEC represents an ideal platform for Porsche. The regulations provide engineers with an unusual degree of freedom to introduce different drive concepts and require forward-looking technologies such as hybridisation, highly efficient engine downsizing and consistent use of lightweight construction. As a result, the WEC provides the perfect platform for Porsche to develop and test innovations for road-going sports cars. The hybrid performance pioneers emphasise the great importance of electrification; at Porsche, innovation is a tradition. Porsche views this new type of “E-Performance” – more power, more driving enjoyment, lower fuel consumption and reduced exhaust emissions – as the performance kit of the future.