Aiming for the Top With Porsche's 919 Hybrid

April 10, 2015
Story By
John Brooks

Le Castellet played the host venue last month for the launch of Porsche's candidacy for endurance racing glory in 2015. Not only did we get a heavily revised Porsche Hybrid 919 but also two new color schemes that will be used at Le Mans.

The red paint job is a homage to the Porsche that started the 16 race win record at Le Mans back in 1970. The Porsche 917 has passed into legend, though it is good to see the drivers, Hans Herrmann (now 87) and Richard Attwood (a mere 75) looking so sprightly. Mr. Attwood still gives instruction to Porsche drivers; alas a good friend had three hours of tuition from the former Le Mans winner when he purchased his 911 GT3 and came away mightily impressed.

The new color drew the media instantaneously, especially when the drivers, Timo Bernhard, Mark Webber and Brendon Hartley were corralled into posing for the pack.

Away from the showbiz elements of the launch the 2015 Porsche, like the revised Toyota TS040, is at first glance is similar to the 2014 car but closer examination reveals massive changes under the skin. When the hybrid formula was drawn up, both Audi and Toyota had existing race cars and quite logically their hybrid racers were developments of their already proven technology. Porsche started with a clean sheet of paper and its showed in their solutions to the challenges posed.

A tiny 2-liter V4 petrol engine that is turbocharged to give over 500hp to drive the rear axle. Alex Hitzinger, LM P1 Technical Director for Porsche explained in simple terms the changes to the engine. "All drive system components were optimized for the 2015 season. The combustion efficiency of the now lighter and more rigid engine has been increased, for example. The V engine’s load-bearing function (90 degree cylinder bank angle) within the chassis was also optimized by means of geometric adjustments that have led to better overall rigidity. The previously used centralized exhaust tract has been replaced by a twin exhaust-pipe system in order to improve output and optimize the vehicle’s aerodynamics."

In addition to this the front wheels are driven by an electric motor that get its energy from two recovery systems. Hitzinger once more, "For 2015 higher output at a lower weight was achieved by a complete redesign of the energy recovery systems. The kinetic energy produced at the front axle when braking is converted into electrical energy. That is the first energy recovery system; the second is installed in the exhaust system, where the exhaust-gas stream drives a second turbine (in parallel with the turbocharger) that acts as a generator. The electricity thus produced – along with that generated by the kinetic energy recovery system (KERS) at the front axle – is temporarily stored in lithium-ion battery cells. The driver can call up additional power output of more than 400hp from this system. This power is applied to the front axle by the electric motor, and it temporarily transforms the 919 Hybrid into an all-wheel drive race car with system power of nearly 1,000hp."

What else had changed on the car? Wolfgang Hatz, Board Member for Research and Development at Porsche AG gave an overview of the changes to the Porsche 919. "We have practically enhanced every detail, but the general concept has remained the same. However, it is a great accomplishment of engineering that the first powertrain concept worked at the first shot, as eventually it was new territory for us. During the 2014 season we were able to put into use some experiences and have continuously improved the hybrid management as well as the aerodynamics. Other measures we could only achieve for 2015, such as the, again, more powerful hybrid system, the weight reduction of the overall vehicle and the new suspension. The mission for the second generation of the 919 Hybrid was: be more efficient, more powerful, but at the same time easier to drive, lighter and more robust.”

Porsche are committed to using the new technology to improve their products sold to customers for everyday driving. Hatz outlined the rationale that drives the race program: "For sure, the greatest improvement comes from the powertrain. For example, in storage technology, i.e. the battery, we have advanced in power densities, which we would have hardly achieved otherwise, thanks to the LM P1 program. This doesn't mean we can transfer that knowledge straight to our road cars, because for daily use the electric range is still more dominant compared to the increase in performance. But by the immense pressure to perform in this top league, we learn an incredible amount in a very short time. Another example relates to the combustion technology. The 2-liter, 4-cylinder turbo petrol engine is the most innovative and efficient downsizing-engine that Porsche has built so far, and it’s definitely a pioneer in terms of its injection. During the development, calculation and validation work for the LM P1 engine, our road car engineers support this program. Thus, the knowledge is generated directly to where it is most important for the company. This also applies to the young engineers in motorsport. If they switch to the road car development, they have a solid education in turbo pace behind them."

So why did Porsche take this route and what benefits does it bring? Hitzinger tries to explain so that even a simple soul like me can begin to understand. "The FIA WEC technical regulations also give engineers plenty of freedom with regard to energy storage medium: flywheel storage, electrochemical supercapacitors (so-called ultracaps) or lithium-ion batteries – the developers tried out everything. In the end, you have to choose the storage device that’s most suitable for the type of hybrid system you’re using. It always comes down to balancing power density and energy density."

Porsche have become the first manufacturer to utilize the maximum level of energy recovery (8 Mega Joules), though Nissan are also claiming this figure. However it is difficult to judge where the Japanese team are as there have been a number of teething issues with their new car, hardly a surprise given the complexity of what they are trying to achieve.

The challenge that faces all of the competitors in this formula is that of reconciling contradictory forces. Once again Mr. Hitzinger comes to my aid. "The higher the power density of the storage unit, the more energy it can absorb and deliver in a short period of time – and the lighter it will be. The reference figure used here is watts per kilogram. Basically, the power density also automatically determines how fast the energy charging and discharging process will be. However, power density and energy density are contradictory parameters."

"In other words, it is physically impossible to keep both at maximum levels. Energy density, in contrast, is the total amount of energy that can be stored. If energy density is low, recovered energy must be quickly used again in order to free up the energy storage unit for the absorption of new energy generated during the next braking sequence, for example. In terms of motor racing, however, it is desirable to be able to accumulate energy through a few curves and then put it to use with the boost function when the car enters a straight. Our batteries achieve a power density nearly as high as that of an ultracap, but have a much higher energy density. In other words, we have a battery that can store and release a lot of power, but its weight is moderate and it also has a relatively high storage capacity."

So what conclusions did we draw from the two days of testing at Circuit Paul Ricard, well not many I am afraid. Porsche topped the time sheets but Audi showed very solid pace over extended runs and Toyota appeared to be keeping their powder dry. The truth is that even after the races this weekend at Silverstone (and next month at Spa-Francorchamps), we will be in the dark about who is really favored to win the big event at La Sarthe. It could be anyone of the three, and who knows, Nissan may just spring a surprise in June. What a few months it's going to be. Watch the video below to see it in action.

Aiming for the Top With Porsche's 919 Hybrid

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