If you're a Steve MacQueen fan or racing car nut, you'll know all about the 24 Hours of Le Mans. If not, the fact
that this endurance race has always sorted out the innovators from the imitators may be news. Exciting news is that hybrid-powered cars are now winning
Le Mans. I gleefully don my overalls and check under some clever hoods to find out how. (Hint: if hot cars don't turn you on, stop reading now.)
Up There with Formula 1 - How?
In fact, hybrids winning at LeMans is not exactly new: they've every Le Mans endurance race since as early as 2012, when AUDI’s R18 e-tron won Le Mans outright. And, before that milestone, AUDI had proven its technology superiority by winning several Le Mans races with its diesel-powered cars.
You may be surprised at the performance: these hybrid cars, which race in the Le Mans Prototype 1 category (LMP1), actually beat Formula 1 cars in acceleration
and straight-line speed. The Porsche 919 Hybrid, the 2017 Le Mans winner, takes just 2.2 seconds to reach 100km an hour, and hits 200km/h in 4.8 secs.
The Porsche 919 Hybrid achieves this level of performance with a turbocharged 2 litre V4 engine. That's pretty puny, so how is it done?
Extreme Testing for New Technologies
‘Le Mans is a precious laboratory in which we can continue to take up the challenges related to the technologies involved,’ says Toyota president Akio Toyoda, ‘putting such technologies to the test in an extreme environment.’ Speed is clearly a factor in the design of LMP1 cars, but the regulations place more emphasis on fuel efficiency, reduced CO2 emissions, and energy-saving technologies. For 2014, for instance, the regulators reduced the amount of fuel LMP1 racers could use by 30%.
The thermal efficiency of modern internal combustion engines is about 37% at best, which means that two thirds of the fuel’s energy is lost in friction, pumping, cooling, transmission, heat, exhaust and accessories. The latest technologies focus on capturing and using more of this wasted energy.
Progress has been rapid: AUDI won the 2006 Le Mans race with a 5.5 litre V12, while Porsche won the 2017 event with a 2 litre V4 that used 40% less fuel. Eventually these technologies will trickle down to production cars, as did the gear-changing paddles you now expect on your steering column.
Kinetic Energy Recovery Systems
Kinetic Energy Recovery Systems (KERS) are potentially road-relevant, energy-efficient power sources. In LMP1 cars, these systems return a big power boost from the energy harnessed under braking by a motor / generator unit. This energy is then stored in batteries or electric flywheels. The Porsche 919 uses a motor /generator on the front axle that captures kinetic energy during braking, which can be released from the battery to boost acceleration. The Infiniti Q60 Black S is rumoured to be the first production car to use KERS technology.
AUDI R18 cockpit with flywheel in the ‘passenger seat' (bottom right). Source: www.racecarengineering.com
The Porsche 919 Hybrid's V4 engine also captures and reuses energy from the exhaust system when the engine is running, with a vane-spun electric generator - driven by the engine’s exhaust pressure - which sends power to the car’s lithium-ion battery pack. This is a first for LMP1 cars. While the V4 engine produces 372 KW, these energy recovery systems raise the 919's total output to 670 KW in race trim. The car’s 875kg weight ensures incredible performance with moderate fuel consumption.
Porsche 919: engine at the rear, battery pack next to the driver and electric motor driving the front wheels.
Racing at the Bleeding Edge
Toyota TS050’s hybrid LMP1 racer is built around a twin-turbo 2.4 litre V6 that produces a total of 730 KW. All other contenders have dropped out of the race: Peugeot, Nissan and AUDI. Peugeot dropped out in 2012 citing Europe’s financial crisis is the main reason. Nissan ran a 930 KW prototype at the 2015 Le Mans race, with a 410 KW engine and a mechanical flywheel that produced an astonishing 520 KW. The front-wheel drive car had a lot of problems and dropped out, followed by Nissan announcing it was dropping out as well.
AUDI has more than proved its technological prowess with 13 wins in the the last 18 years, and the reason it dropped out was not because of performance: it was parent company VW’s global Diesel emissions cheating scandal (Dieselgate) and the multi-billion dollar fines that followed.
That leaves Porsche and Toyota, which has been unlucky not to win one of the last few events; in 2016, Toyota was robbed of a sure win when the lead car
broke down on the last lap of the 24 hour race. A few hearts must’ve broken at the time, too.
Other innovations include direct fuel-injection systems that work at pressures exceeding 34,800 psi (AUDI R18), which ensures better fuel vaporization in the combustion chamber. This means more complete burning of fuel, which results in increased power output and reduced emissions.
The AUDI’s KERS system relies on a flywheel that operates in a vacuum, and is driven by an electric motor that can spin it up to 40,000 rpm. When the flywheel spins at high speed, the flywheel motor acts as a generator and sends electricity to an electric motor on the front axle.
The R18 even features laser high-beams with GPS-linked swivelling action that can be programmed for each track the car races on.
It’s early days for these technologies, and the LMP1 race cars that are loaded with them have had more than a few problems lasting the 24 hour distance, causing Akio Toyoda to concede that ‘hybrid technology might not yet be ready for the long distance of the 24 Hours of Le Mans.’ It’s only a matter of time, of course, and Le Mans is an equally tough test for conventional racing cars.
Porsche’s 919 Hybrid Racer, via Road and Track
10 things you need to know about the AUDI R18, via Car and Driver
Toyota Hybrid Tech not ready for Le Mans?, via Motorsport
Nissan’s Le Mans racer explained, by Top Gear
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