The biggest change to the 24 Hours of Le Mans grid this year is the arrival of LMGT3, which has supplanted GTE as the event’s production-based class. Aside from boosting car manufacturer numbers from four to nine, the introduction of GT3 machinery has brought some differences in how the race will likely run, as well as retaining some similarities. We look at the key battlegrounds.
To the layperson, GT3 and GTE cars may look very similar, if not the same. But the former has traction control and anti-lock braking, plus more weight and slower lap times by around four seconds at the Circuit de la Sarthe. The GT3 top speed is also 15-20km/h less than in GTE, whilst the GT3s will be doing much shorter stints. In most series, it is common for GT3 cars to do one hour before pitting, but at Le Mans they are expected to complete only around 40 minutes. This means that cars will be pitting more, likely in excess of 30 stops, whereas last year’s winning GTE-Am car completed 24.
GT3 cars at Le Mans have a limited amount of energy (measured in MJ) they can use during a stint. This number is defined in a Balance of Performance table. Teams calculate how much energy they can use per lap and instruct the driver to reduce the consumption rate, using familiar tactics such as lift and coast. Energy can also be saved during a safety car, when the pace is reduced. Fuel and energy consumption rates typically correlate on a standard racing lap, but in safety car conditions, more fuel is used than energy. The 40-minute stint estimation is based on Le Mans being an energy-intensive circuit, due to its long straights. When a car pits to replenish its energy allocation, it will still have fuel left in the tank.
‘Everything is done on energy, not fuel,’ says Aston Martin Racing head of performance, Gustavo Beteli, who has engineered GTE and GT3 programmes at Le Mans. ‘There is mileage in the energy – getting the best lap time for the least amount of energy is key. Whereas before, you would just run to the fuel and go again. Now, the energy varies a lot. In safety car laps, you use a very small amount of energy, so you can extend your stints. You try to do that the whole race, to minimise your pit stops.’
Torque sensors are a new variable in the GT ranks. These devices are fitted to the driveshaft and collect data that determines the car’s energy consumption. Sudden increases in torque sensor data are investigated and can be penalised. As is the case…
Click Here to Read the Full Original Article at Racecar Engineering…