Toyota is continuing its effort to be the first Japanese manufacturer to score an overall victory at the 24 Hours of Le Mans since Mazda won the race in 1991 with the ear-splitting four-rotor 787B.
Its 2014 contender, the TS040 Hybrid, will vie with incumbent favorite Audi and Porsche’s long-awaited return to the race’s senior class. All three manufacturers’ cars conform to new rules this season that aim to boost the efficiency of the racers.
That means stronger hybrid-assist motors, but it also means 10 cm (4 in) narrower cars for reduced frontal area and 5 cm (2 in) narrower tires for reduced drag and rolling resistance.
New rules mandate a 25% reduction in fuel consumption, and impose a limit on maximum fuel flow as measured over a three-lap average. Fuel-flow limits in Formula One have already caused controversy this season, so it remains to be seen how effectively this can be policed.
The fuel-flow allowance is variable, depending on how much electric assist the team has built into the car. Toyota has opted for a system applying 6 MJ of hybrid-electric capacity per lap. The available options are no hybrid assist, or boosts of 2, 4, 6, or 8 MJ per lap.
In the case of a car with 6 MJ or less electric assist, 87.9 kg/h of gasoline flow is permitted, or 78.3 kg/h of diesel. This gives a slight advantage in available energy per lap to the gasoline engine.
While the TS040 is built on an evolution of last year’s TS030 chassis, there is a big change in the drivetrain: now the car is all-wheel drive. In addition to the 520-PS (382-kW) 3.7-L naturally aspirated gasoline V8 internal-combustion engine and its Denso electric assist motor driving the rear wheels, the TS040 adds an Aisin electric motor/generator to the front axle. Together the two electric motors add 480 PS (353 kW), for an event 1000-PS (735-kW) total that is available under acceleration. The dual electric motor/generators send power to and receive it from a Nisshinbo supercapacitor, via the power inverter.
"We looked at various possibilities, but the most appropriate solution for us was to increase the displacement of the engine to improve heat efficiency whilst upgrading the hybrid system," concluded Hisatake Murata, General Manager of Toyota's Motorsports Unit Development division. "We considered bigger hybrid capacity, but settled on 6 MJ, as anything greater, using kinetic energy recovery, had a negative effect on lap time due to increased weight."
That decision triggered the move to all-wheel drive, for its potential for greater brake regeneration. "To recover that amount of energy under braking, the rear motor-generator was not enough, so we returned to the four-wheel hybrid concept we developed from 2007 to 2011, before regulations limited hybrid boost to just one axle," he said.
Weight was a bigger factor this year, too, because of a 45-kg (99-lb) reduction in the minimum weight. "The main challenge has been to create a more complex car with more hybrid hardware to achieve higher hybrid power and at the same time reduce significantly the weight due to a 45-kg reduction in minimum weight," remarked Pascal Vasselon, the team's Technical Director. "That has been a real headache, but using lightweight materials and efficient design optimization processes, we have achieved our targets."
Toyota points out that it first won an endurance sports car race with an all-wheel-drive hybrid when its Supra HV-R won the Tokachi 24 Hours in 2007. As with the TS030, the new car was designed, built, and is operated by Toyota Motorsport GmbH, of Cologne, Germany. This was previously the Toyota Formula One racing operation before the company turned its focus to sports car racing.
The company not only has its own wind tunnel there, but it also employs simulation and hardware-in-the-loop technology to test individual components to optimize designs in the absence of track testing.
“I really, really, really can’t wait to race this machine because I think it is a really good one,” enthused driver Alex Wurz. Results from the first open test of the season at Circuit Paul Ricard show why: cars from all three manufacturers circulated within a fraction of a second of one another.
"It is very interesting to see what the other competitors are doing with their car and to see the performance," observed driver Kazuki Nakajima at the pre-season test. "The results have certainly been very interesting and there is always something to learn. There is still some time before the first race. It is a big help to test with all the other teams because this year we have a new focus on fuel efficiency so we are saving much more than before."
Nakajima also said he is pleased with the new car's ergonomics. "The car is very well built and much more comfortable to drive this year, with revised driving position and better visibility," he noted. "That will help the drivers during the long races, especially Le Mans."