Compare and contrast
The 2021 FIA World Endurance Championship saw the debut of the Hypercar class, comprising a two-wheel-drive car built by Jim Glickenhaus’ team and a four-wheel-drive hybrid from Toyota. In 2023, LMDh cars will also be eligible to race in the WEC, and in the American IMSA series, with a two-wheel-drive hybrid. It therefore makes sense to look at the available data from 2021, and make a comparison between the two very different configurations.
After a season of racing, both the understanding of the rules and the lap time simulation tool the author coded and used to analyse LMH cars performance has improved significantly and this, together with the data collected during 2021, enables a much better understanding of the real state of play in this new class.
Key parameters
With the tyres being supplied solely by Michelin, who should ensure level performance between their rubber for different cars, there are four other crucial parameters that influence how LMH vehicles perform:
• Overall traction power
• Mass
• Aerodynamics
• Powertrain architecture (hybrid or traditional)
The first two points are tightly regulated and are factors the FIA and ACO constantly monitor and use to balance the cars’ performance.
In terms of powertrain, the rules mandate the power window each car must be able to produce, providing power curves the engine designers must stick to. The window of maximum power is between 480 and 520kW, plus three per cent tolerance. The regulators monitor cars’ compliance to the rules using driveshaft-mounted torque sensors.
During the first season, Toyota and Glickenhaus were given different weights and powers, to try and bring them closer together in terms of pace. This was also done to compensate for the Toyota having an electric motor pulling the front wheels and, according to the rule set, being all-wheel drive above 120km/h (with a dry track). At Le Mans, the Toyota had a minimum weight of 1066kg and a maximum power of 515kW, while the Glickenhaus ran with 1030kg and 520kW.
The overall target referred to an aerodynamic efficiency (lift-to-drag ratio, or L/D) of about four, although Racecar understands that the final target mandated by the class regulations was slightly higher than this.
Downforce and drag
This is only a part of the story though. The teams are also given a window in terms of maximum and minimum downforce and drag their cars can produce, with the possibility to vary aerodynamic properties by adjusting only one single aerodynamic device (the rear wing, for example).
