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Porsche 918 Hybrid

Data:  2015-11-22

Porsche 918 Hybrid

Electric motor: 295 kW, drives front wheels
Internal combustion engine: 2.0V4 turbo 370 kW, max 9000 rpm, drives rear wheels
Gearbox: 7-speed sequential, hydraulically operated
Wheels and tyres: 14x18 BBS forged magnesium wheels with 310/710-18 Michelin tyres front and rear
Dimensions: 4650 x 1900 x 1050 mm
Weight without fuel: 870 kg / 1918 lb by the regulations
Fuel tank: 68.5 L

While the three versions of the 2014 919 looked cool, the 2015 version looks even better after the nose job. The first decisions regarding the 919 Evo (919-15) had to be made even before the 919-14 had entered its first race. Back in April 2014, a small group of specialists got together to define the most important parameters for the second-generation monocoque and chassis. The 2014 model was refined in detail after the 24 Hours of Le Mans in June, but by that time the 2015 car had become the top priority. The 2015 model had its first roll-out on December 15, 2014 at the Weissach test track in the hands of Marc Lieb. The air temperature was 0ºC/32ºF. Due to the winter weather in Germany, extensive testing was done on Abu Dhabi’s Yas Marina Circuit in January 2015. The internal combustion engine didn't receive any power increase, but the front axle electric motor got 295 kW for the 2015 season (185 kW in 2014).

The monocoque is a carbon-fibre sandwich construction that was completely redesigned for the 2015 919 hybrid. For the 919-15 it is manufactured as a single unit, rather than in two sections. Its weight was reduced. A new structure for the chassis in general and the rear-body in particular also helped to increase rigidity and reduce weight. An important development goal with the all-new chassis was to improve handling, particularly in terms of counteracting understeering in corners. The most noticeable changes to the carbon-fibre skin of the Porsche 919 Hybrid involve the new front end and the leaner engine cover in the rear. Changes to the wheel design were necessitated by the regulations. In order to limit aerodynamic benefits, 50 per cent of the wheel surface has to be open now.

There are four formulas with electric boost levels ranging from 2 to 8 mega joules (MJ) per one lap of Le Mans circuit. The more electricity you use, the less fuel you are allowed to use. The calculation formula is based on the 13629-metre Le Mans lap, and the calculation is adjusted accordingly for the other seven racing circuits. For example, if a team wants to utilise 8 megajoules per lap, an FIA flowmeter device will limit the permitted amount of fuel per lap to 4.76 litres (this is equal to average fuel consumption of 34.9 L/100 km). By comparison, 5.07 litres of fuel can be used per lap in the 2-megajoule category (average allowed fuel consumption 37.2 L/100 km). Engineers also have to take into account the fact that the more powerful the energy recovery and storage systems are, the bigger and heavier they tend to be. While the 919-14 was designed for the 8 MJ formula, it was finally homologated for the 6 MJ formula. The 919-15 was homologated for the 8 MJ formula making Porsche the pioneer. Relying more and more on electricity and less on fuel is the future-thinking.

The electric power is applied to the front axle electric motor, and it temporarily transforms the 919 Hybrid into an all-wheel drive car with system power of around 1000 hp.The kinetic energy produced at the front axle when braking is converted into electrical energy. The second energy recovery system is installed in the exhaust tract, where the exhaust-gas stream drives a turbine (in parallel with the Garrett turbocharger), that acts as a generator. The electricity produced is temporarily stored in lithium-ion battery cells. The WEC regulations give engineers plenty of freedom with regard to energy storage medium. Audi and Nissan use flywheel storage, Toyota uses ultracaps (electrochemical supercapacitors) and Porsche uses lithiumion batteries. Porsche developers tried out all of these before making the decision.

2015 FIA WEC LMP1 rules

(From Porsche press materials, April 12, 2015)
Several changes were made to the regulations for the 2015 season, all of which Porsche supported.

The LMP1 qualifying session in the WEC has been shortened from 25 to 20 minutes. Two drivers will still participate in each session. However, the qualifying time will be calculated by adding each of their fastest laps together and then dividing the result by two. The rules for 2014 used the average of a total of four laps – the two fastest ones for each driver. In 2015, every driver can use a fresh set of tyres, which enables a true comparison of the results.

The number of engines that may be used per season has been limited to five. This is a cost-control measure, especially as it prevents the possible development of engines with a specific Le Mans specification.

An assumed average weight of 80 kilogrammes per driver has been introduced for the 2015 season. This continues to give lighter drivers a small advantage in their respective cars. But in general it helps favour the fastest drivers rather than just the lightest ones, and thus serves to counteract drivers’ attempts to gain an edge through extreme dieting.

New limitations have been placed on the test days in 2015. A team may only conduct totally private tests on a maximum of ten days. On another ten days, tests can be conducted “openly", provided the dates are announced 30 days in advance. On these days, other competing teams may also test their vehicles. The largest segment of test days – an additional 30 – must be planned well in advance and registered 90 days beforehand. Here, as well, the competition must be allowed to participate.

As part of the effort to control costs, the maximum number of team members working on-site has been limited to 65 for a two-car team for the races following Le Mans.

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