The engine is a turbocharged 16-valve 2.0-litre direct-injection engine and has an unusually wide V angle, although the exact figure remains unknown. Unlike Audi’s LMP1 car, the turbocharger is not electric.
The V4 is one of the least popular in automotive engineering because of the inherent problems with the configuration in achieving smooth running, and none have been used in recent history by a top flight motorsport team - either in sports cars or at Le Mans.
Nonetheless Porsche is believed to have adopted the highly unorthodox layout predominately for packaging reasons, allowing the optimum positioning of the 919’s battery-fed hybrid drive system.
Other reasons for the choice could include simplicity, the inherent stiffness of such a short block, the torque-generating ability of a large capacity four-cylinder motor, fuel consumption (critical in the new energy-based formula), and lightness.
It is likely the engine will use balancer shafts to cancel out the otherwise unavoidable vibrations of the fundamentally unbalanced V4 design.
However some flat four engines, such as those used by Porsche at Le Mans in the 1950s, have been described as having a 180 degree vee, so this possibility cannot at this stage be entirely discounted.
Porsche has already announced that the 919 will have four cylinders and two recuperation systems that will store energy in a battery until it is deployed by the driver through an electric motor driving the front wheels. Autocar can reveal more details about this system.
The petrol engine drives the rear wheels with an electric motor sitting up front powering the front wheels. The two energy recuperation systems are called KERS and ERS (the ERS is called AER by Porsche, AER standing for Abgasenergierueckgewinnung, Abgas being the German word for exhaust).
The KERS recovers kinetic energy from the brakes on the front axle, the ERS operates via the exhaust gas on the turbocharger. The battery is a lithium-ion unit supplied by US-based A123 Systems.
This hybrid set-up is similar to the system used by Audi but different to the system used by fellow Le Mans rival Toyota, which has KERS on both the front and rear braking system. Porsche thinks the recuperation on the rear brakes is not efficient enough, hence why its system differs.
The regulations only allow two energy-recuperation systems.
Porsche has also announced that the 919 will contest the entire 2014 World Endurance Championship (WEC) but with a specific focus on the Le Mans 24 hours. Drivers known to be driving include Mark Webber, former Le Mans winners Timo Bernhard and Romain Dumas and Neel Jani. Brendon Hartley and Marc Lieb are other names in the frame, according to Autocar’s sister publication Autosport.
The Porsche 919 will make its race debut when the 2014 WEC kicks off on 20 April with the Silverstone Six Hours. Thereafter the series visits Spa, Le Mans, Interlagos, the Circuit of the Americas in Texas, Fuji in Japan, Shanghai and Bahrain.
Two cars have been built so far, the original chassis from 2013 and a new one that was used in a test at Bahrain last week. A third car is under construction. The next test will be in Bahrain in mid-February.
Other manufacturers to use V4s include Lancia and Ford whose engines were also used by Saab.
Greg Kable and Andrew Frankel