Porsche
919 Hybrid
Porsche
is returning to the top category of the famous endurance race classic at Le
Mans and the World Endurance Championships (WEC) for sports cars with its newly
developed 919 Hybrid. The LMP1 prototype, which is designed for extreme
efficiency, is the most complex race car that Porsche ever put on wheels.
It
serves as a research platform for fundamental technology to be used in future
production models, with its combination of two different energy recovery
systems and a downsizing turbocharged engine. So the real winner of Porsche
factory racing is already clear: it is the customer.
The
exceptional efficiency of the highly complex technology of the Porsche 919
Hybrid is the result of a carefully balanced overall concept. From the
combustion engine to the energy recovery systems, chassis and running gear,
aerodynamics and driver ergonomics, the sum of all individual components forms
an exceptionally effective unit. It all serves one goal: a maximum of sporty
performance within tight fuel economy constraints.
In
choosing a hybridised drive concept, the newly formulated WEC regulations gave
Porsche developers great freedom. The drive system of the new LMP1 race car is
based on a four-cylinder petrol engine that is as compact as it is lightweight.
It performs load-bearing functions within the chassis based on its
V-construction, which also offers thermodynamic advantages. The petrol engine,
which reaches a maximum engine speed of around 9,000 rpm, is a frontrunner in
terms of its downsizing philosophy with its 2.0 litres of displacement, direct
injection and monoturbo charging.
It
also features two different energy recovery systems. Fundamentally new and
especially innovative is the recovery of thermal energy from exhaust gases. An
electric generator is used here, which is powered by the exhaust gas stream.
The functionality of the second hybrid system is known from the Porsche 918
Spyder. Here, a generator on the front axle utilises braking phases to convert
kinetic energy into electric energy. It is also stored in highly-advanced
water-cooled lithium-ion battery packs until the driver needs the extra energy.
Then the front generator is operated as a single electric motor and drives the
two front wheels via a differential in the acceleration phases. This gives the
Porsche 919 Hybrid a temporary all-wheel drive system, because the petrol
engine directs its power to the rear wheels in a conventional way.
Intelligent
management of this additional available energy assumes a special role here. Of
course, the strategic focus of the racing engineers is always on the most
efficient use of available power. This means an optimal lap time. The driver
can choose from several automated drive modes that have an effect on vehicle
dynamics as a function of the traffic situation, course layout and weather
conditions. At this point, the developers made use of knowledge gained by
Porsche with the 911 GT3 R Hybrid, including at the 24-hour race on the
Nürburgring.
The
allowable petrol fuel consumption depends directly on the amount of electrical
energy that the driver can call up per lap in what is known as the Boost
function. Race rules distinguish between four levels ranging from 2 to 8
megajoules (MJ). Porsche is developing the 919 Hybrid for the "Premiere
class" with an energy recover capacity of 8 MJ. This requires the use of
high-performance energy recover and storage systems, which need to be sized
larger and heavier. A flow meter device also limits the amount of fuel flow.
Example of Le Mans: Here, the turbocharged petrol engine, which is driven at
full load for 75 per cent of the 13.65 kilometre lap, only has 4.64 litres of
fuel available. In the 2-MJ class, the figure is 5.04 litres.
