Navigant Research Blog

Hybrid Race Cars Dominate the Le Mans 24-Hour Race, Again

David Alexander — July 6, 2014

The annual 24-hour endurance race at the Le Mans circuit is famous for presenting both car and driver with a grueling challenge.  The goal is quite simple – teams of drivers and mechanics battle to see who can complete the most laps of the circuit in 24 hours of driving.  The Fédération Internationale de l’Automobile (FIA) organizers set rules for the vehicles taking part, such as minimum weight and limitations on the use of four-wheel drive, so it’s not simply a case of developing the most powerful engine.

In this month’s 82nd running of the race, Audi secured its 12th victory in 14 years with a one-two finish.  The Audi team’s No. 2 car finished with 379 laps, three more than its No. 1 team, and Toyota took third place.  The winning team overcame turbocharger problems for its third success in the world’s most famous endurance race, watched by 263,000 spectators – the highest attendance in 20 years.  The  Porsche team was in second place overall with its new vehicle when it was forced to retire in the 22nd hour with technical issues.

Full Day’s Drive

The race is won by a combination of performance and reliability, and the winners had to replace key engine components, such as the fuel injector and turbocharger, along the way.  With speeds exceeding 200 mph along the straights, the Le Mans race gives auto manufacturers an extreme testing ground for the technology that often ends up in production vehicles.  With a lap distance of just under 8.5 miles, the winning car traveled just over 3,200 miles in 24 hours.

This year, Audi, Toyota, and Porsche all raced different variants of hybrid drive:

  • The Audi R18 e-tron quattro couples a mid-mounted 3.7-liter V6 turbo diesel injection engine powering the rear wheels with a hybrid system on the front axle, which uses a flywheel energy storage system.  The 2014 model features an electric motor linked to the engine’s turbocharger that converts thermal energy from the exhaust gas into electric energy.
  • The Toyota TS040 HYBRID also features a four-wheel drive hybrid boost system for the 3.7-liter V8 gasoline engine.  Toyota Racing is using an Aisin AW motor-generator on the front axle to complement the DENSO unit on the rear.  Under deceleration, the motor-generators apply braking force in combination with traditional mechanical brakes to harvest energy, which is transferred via inverters to store in a bank of ultracapacitors.  During acceleration, the stored energy delivers a power boost as required at each axle.
  • Porsche’s 919 Hybrid drive system is based on a 2.0-liter V4 gasoline engine.  The engine is a structural component of the chassis and features direct injection, a single turbocharger, and thermodynamic energy recovery capabilities.  Two different energy recovery systems charge the lithium ion battery pack used for energy storage.  One is the recovery of thermal energy by an electric generator powered by exhaust gases.  The second hybrid system is a motor on the front axle using regenerative braking to convert kinetic energy into electric energy.

It’s fascinating to see major manufacturers testing their hybrid technology under race conditions.  In 2012, Peugeot, which won Le Mans in 2009 with a diesel hybrid race car, had to withdraw funding for its team.  Motor racing is an expensive sport.  But lessons learned by all participants about thermal energy recovery, lightweight vehicle structures, and the relative performance of gasoline V4, gasoline V8, and diesel V6, as well as the different energy storage options, can deliver valuable benefits when translated into production vehicles.

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