Porsche reveals its hand

Returning Le Mans king opts for hybrid V4 power | By Gary Watkins

Porsche has finally disclosed technical details of its 2014 World Endurance Championship challenger and confirmed two of the worst-kept secrets in motor racing. The internal combustion element of the Porsche 919 hybrid’s powertrain is a 2-litre V4 and its energy storage system is made up of lithium-ion batteries.

The Stuttgart manufacturer had only previously confirmed that its new Le Mans 24 Hours contender would be a petrol-powered turbo and that one of its two energy-retrieval systems was driven by exhaust gases from the engine. The full specification of the car, minus output figures, was released after a successful four-day test at the Bahrain International Circuit in mid-February. Porsche LMP1 technical director

Alex Hitzinger explained that the decision to opt for a small-capacity turbo and vee configuration was driven by weight reduction.

“There is an incentive built into the regulations to have a very big [capacity] hybrid system,” he said. “To be able to fit a big hybrid system, you have to have a very light base car. One way to achieve this is to downsize to a small-capacity, highly turbocharged direct-injection engine.”

He explained that a vee configuration allowed the engine to be mounted as a structural component, avoiding additional weight and complexity.

The choice of lithium-ion batteries offers the best compromise between energy density and power density, respectively the amount of energy that can be stored and the rate at which it can be stored and discharged. “For the given requirements, it is the lightest option,” he said.

Hitzinger confirmed that Porsche planned to run at the highest level of energy retrieval, eight megajoules per lap of Le Mans, that the 2014 LMP1 regulations allow.

The announcement from Porsche means that this year’s three factory LMP1 contenders have each chosen different energy-storage options. Respectively, Audi and Toyota have retained flywheel and super-capacitors from their first-generation hybrid P1s of 2012-13.

Porsche’s exhaust-driven recovery system is subtly different to those used on the 2014 Audi R18 e-tron quattro and in Formula 1. It has a separate turbine in the exhaust system, rather than taking drive directly from the turbocharger.

Porsche will unveil the 919’s race livery at the beginning of March and confirm the driver line-ups in each car. It is known, however, that it will split up long-time team-mates Timo Bernhard and Romain Dumas: Bernhard will share with Mark Webber and Brendon Hartley, Dumas with Neel Jani and Marc Lieb.