The optimal deployment strategy can be broken down as follows:

Accelerate as hard as you can out of the corner.

Lift off the throttle near the end of straight to save energy (PMotor drops to zero, and car slows gradually).

“Braking” is then performed in two steps:

Pull the regen paddle (rRegenPaddle) to recover electrical energy from the rear axle and start slowing the car.

Use the brake pedal for the final part of retardation to apply the front brakes in order to get the correct corner entry speed.

It is an annoyance for drivers and engineers alike to split braking into two phases. With the Gen2 car teams have to do this in order to maximise energy recovery. Any energy that goes into the front friction brakes is wasted as heat so the front brakes are only used in the final few meters before the corner. This is a crazy situation because drivers are using the regen paddle to do the majority of braking instead of the actual brake pedal which is only used in the second part of braking to finesse the final car speed.

By adding front regen, the Gen3 car gets rid of the need for a regen paddle. The brake pedal is wired up to both the front and rear motors which are applied simultaneously. There is no longer a need to use the rear regen first, followed later by the front brakes, because both axles now recover energy so nothing is wasted by applying them together (assuming they have similar efficiency). This means that drivers can brake harder using both axles allowing them to attack the corners, and more importantly they can use the actual brake pedal to do this. Good riddance to the regen padle!

30sec Charging Pitstop

As part of the tender, the spec includes the provision to do an optional pitstop for 30sec of fast charging. We were keen to simulate whether it is better to use more energy then stop to recharge, or conserve energy and stay out on the track.

First we need to makes some assumptions about the battery capacity and charging rate. The current technical regs state a 280kg maximum battery weight, while the target weight for the new battery is 284kg. The increased charging power might put additional demands on the battery in terms of heat dissipation and cooling, so for argument sake, let’s assume a similar race energy limit of 52kWh. Since the battery system is designed for 350kW regen from the rear axle and 250kW from the front, i.e. 600kW total during racing, we assume that pitstop charging would occur at a similar rate. Some power would be lost to battery efficiency, and rounding down for simplicity means that teams can top up their cars by 4kWh.

If we run an energy sweep, we can see how the laptime varies for different levels of energy saving. The current race format is 45min + 1 lap. We can use the laptime at each energy level to calculate the number of laps (plus 1) that can be completed(NLapsTimeLimit). We can also calculate how many laps can be completed at this energy level before the battery runs out (NLapsEnergyLimit). Where the two lines meet in the figure below (at the cursor) represents the quickest the car can be driven without that battery running out. Without a pitstop it can complete 34laps with the Gen3 car (3 laps more than at Marrakesh this year):

Sweep of energy per lap showing laptime and number of laps possible

To look at the pitstop scenario, let’s assume that for Marrakesh the pitlane time loss (versus staying on the circuit) is 15sec, so cars would lose a total of 45sec by stopping to charge. If we repeat the NLapsTimeLimit (red line above) calculation with 45sec taken off, and add 4kW to the NLapsEnergyLimit (green line) calculation then the curves intersect again at 34laps. It’s too close to call so we need to drill down into the laptimes.

With no pitstop, the best laptime for 34laps is 1m20.71s. With the extra energy from a pitstop this improves to 1m19.40s i.e. 1.31sec faster. Over a 34lap race the stint time with pitstop is 44.54sec quicker, however if a pitstop takes 45sec, then it will be a very close call indeed.

Is there anything to watch out for?

Overall we think the changes represent a big step forwards in terms of racing, simplicity and developing road relevant technology. All those involved at the FIA and FE teams in shaping this specification deserve to be congratulated for designing what appears to be a well thought out future. There are a couple of things that we would keep an eye on; with 300kW motors, the cars consume energy much quicker so the drivers have to lift off the throttle earlier (around halfway down the straight). Perhaps this is why the tender includes a scenario B for 250kW rear motors which would run for longer down the straights. Teams might also have to watch out for battery overheating with the massive increase in power going into and out of the battery. As well as balancing energy usage, battery thermal management might once again become a crucial part of the championship battle.

The spec is likely to evolve as the various tenders come in and it becomes apparent what is possible from a technological standpoint. We can’t wait to find out what will happen, and will be ready to provide simulations to FE teams to arm them with the knowledge required to extract maximum performance from the Gen3 cars.