Hybrid transmission zones for Le Mans - image courtesy ACOEnlarge Photo
This year's 80th 24 Hours of Le Mans features four hybrid cars on the 56-entry grid, where last year there was only a single hybrid from Hope Racing, using a Flybrid flywheel system rather than the standard - to OE vehicles - battery pack.
This year's hybrid entries come from two of the world's larger manufacturers: from Toyota Racing, who have a brace of TS030 Hybrid LMP1 prototypes and Audi, bringing two of their e-tron quattro cars. The Toyota machine uses petrol, while the Audi runs on diesel fuel.
To prepare for this weekend's test day in advance of the June 16-17 twice-around-the-clock FIA World Endurance Championship race (race No. 3 for the WEC), the Automobile Club de l'Ouest (ACO) decided to create specific zones where the four cars in question can transmit energy recuperated under braking - there will be seven such zones on The Sarthe circuit.
The hybrid systems designed by Toyota and Audi recover energy generated under braking, storing and then transmitting this energy during acceleration. To limit the size of the systems - and the budgets required for their development - the ACO and FIA joined together to impose a maximum quantity of energy that can be transmitted between two braking phases at 500 kilojoules. Each hybrid car can take advantage of this added electric power without exceeding the rules decreed in the race's technical regulations.
The FIA and ACO defined five zones during the second race of the season at Spa-Francorchamps early in May, where the system was used for the first time. On the lengthy Le Mans circuit (13,629 km or 8.469 mi) they decided to institute seven zones.
To establish clearly-defined zones that allow the 500 kj maximum energy to be transmitted between two braking phases, the ACO and FIA defined zones on the Le Mans track where braking is sufficiently heavy to be taken into account. The entry to each zone is 50 meters before the corner in question; both the No. 1 and 2 Audi cars and the No. 7 and 8 Toyota cars will have to respect these new zones, beginning with the test session prior to the week-long festivities surrounding the Le Mans race itself.
The first zone is at the Dunlop chicane shortly after the start/finish line; the second is at the Forza Motorsport chicane one-third through the long Mulsanne while the third is at the Michelin chicane two-thirds down the same road. The fourth zone occurs at the Mulsanne corner while the fifth is at Indianapolis corner, always a great overtaking zone. The sixth zone is at Porsche corner and the final zone is at the Ford corner shortly before the front straight and pit entry. In the accompanying image, marshal posts are noted for each braking zone.
The hybrid solutions from Toyota and Audi are quite different. The Audi e-tron quattro feeds its energy to the front drivetrain when the car is running in excess of 120 km/h so that the transmission can take place. In the Toyota the energy is fed to the rear drivetrain without minimum speed.