Porsche pulled the wraps off its 2016 919 Hybrid racer this week. The World Endurance Cup series will have its last official testing program this weekend at the Paul Ricard racing circuit in southern France. The first race of the season will take place at Silverstone in England on April 17.
The regulations for WEC Le Mans Prototype 1 (LMP1) cars are designed to push engineers to experiment with new technologies that will be relevant to road going production cars. In an age when governments around the world are requiring manufacturers to reduce the greenhouse gas emissions of their cars like never before, that puts the focus squarely on efficiency.
This year, the rules have restricted how much fuel each car may consume. That limitation means the turbocharged V-4 engine that is at heart of the Porsche 919 Hybrid powertrain is less powerful than it was in last year’s car. Porsche estimates the reduction in power would translate into lap times at Le Mans that are about 4 seconds a lap slower than last year.
To claw back some of that lost performance, Porsche engineers have devoted an enormous amount of time to improving the car’s regenerative braking system (KERS) and the thermal recovery technology that turns exhaust heat into electricity. The gasoline engine drives only the rear wheels. Electricity from the KERS unit and the thermal recovery system is stored in a liquid cooled lithium ion battery and is used when needed to power an electric motor for the front wheels.
When it comes to that link between race cars and road cars, consider this. The 919 Hybrid electrical system operates on 800 volts. Where have we heard that number before. Oh, yeah. That’s right. The all new 4 door electric sports car that Porsche is working on, the Mission E, is also rumored to use a powertrain that uses 800 volts. Does racing improve the breed? You betcha!
Porsche says it decided to get back into WEC racing precisely because the rules encourage innovation that is relevant in the real world. Manufacturers are free to use either gasoline or diesel fuel. 4 cylinder, 6 cylinder, and 8 cylinder engines are permitted. Various forms of energy recovery are allowed. The only thing race engineers have to decide is, which combination of components will be the most efficient?
The thermal recovery system is a very cool device — no pun intended. Not only does it harvest electricity from exhaust heat that would otherwise be wasted, it uses some of that recovered energy to keep the turbocharger spinning at high speeds even when the driver’s foot is off the throttle.
One of the downsides of turbochargers is they only provide maximum boost when they are spinning at 100,000 rpm or more. When a car is coasting or braking, those revs drop quickly and it takes a moment or two for the turbo to spin back up to speed when the drivers whistles down to the engine room for more power again. The harvested electricity keeps the turbo spooled up at all times, eliminating turbo lag completely.
The popularity of World Endurance racing is growing while that of Formula One is declining. One reason is that Formula One rules severely limit innovation. That restriction has convinced manufacturers like Porsche and Toyota to put their money and engineering talents to work in WEC competition rather than Formula One. Former F1 driver Mark Webber was part of the driving team that won the WEC championship for Porsche in 2015.
More and more F1 drivers say they would be interested in endurance racing. Double world champion Fernando Alonso has said he would like to try his hand behind the wheel of an LMP1 car, but his team, McLaren Honda, refuses to allow him to compete in anything but Formula One. Suffice to say, the organizers of the World Endurance Cup are looking to the future. Formula 1 seems to be forever focused on the past.
Photo credit: Porsche