Ansys and Porsche Motorsport: Building on a Winning Legacy With Simulation

For this installment of “Ask the Engineer,” a Porsche Motorsport insider talks powertrain efficiency in the new Porsche 99X Electric GEN3 Evo all-electric race car.

There’s a new Porsche in town, and it’s already shaking up one of the most electrifying series in motorsport, the ABB FIA Formula E World Championship. The TAG Heuer Porsche Formula E Team, led by reigning Drivers’ World Champion Pascal Wehrlein and 2020 Champion António Félix Da Costa, is ready to make racing history once again in the new Porsche 99X Electric GEN3 Evo all-electric race car.

The 99X GEN3 Evo made its debut in the São Paulo E-Prix as the quickest accelerating FIA single-seater, capable of going from 0-60 mph in just 1.82 seconds. Wehrlein kicked it off with a 1-minute, 9.851-second pole lap from the P1 grid slot — three seconds faster than last year. This performance, as well as Da Costa’s early podium win, jump-started what promises to be an exciting season for the team.

The basic rules of engagement are the same, including available energy restrictions. However, this year teams can engage front-wheel drive during qualifying duels, race starts, and attack mode. With this new development, the Porsche 99X Electric GEN3 Evo benefits from the additional grip of temporary all-wheel drive as the front and rear wheels are engaged simultaneously.

For Leonard Mengoni, development engineer, high-voltage power units at Porsche Motorsport, these new developments are just business as usual. We had the chance to talk to him about his work and how the Ansys-Porsche partnership will continue to drive powertrain efficiency in Porsche Motorsports.

For starters, what’s different about the Porsche 99X Electric GEN3 Evo from an efficiency standpoint?

Mengoni: The new car generates a maximum of 350 kilowatts peak power. There are now two situations (race start and attack mode) in the race where that maximum output can be distributed differently than before. For the first time, we have all-wheel drive and traction control, so you can control your powertrain to prevent your tires from spinning and get more traction when accelerating.

Specifically, with the addition of all-wheel drive the car behaves a little differently. You have a different rotation when you accelerate because you’re not only pushing from the back. What this means is if you have the car in active all-wheel drive, it pulls the car out of the corner, so you have more longitudinal acceleration because all four wheels are driven by the electric powertrains. Additionally, we have new tires that offer more maximum grip than before.

Because rear- and all-wheel result in different operating points for front and rear powertrain, and additionally with traction control, your distribution of operating points also gets a bit wider.

How are you using Ansys tools to maximize the efficiency of the new powertrain package?

Mengoni: For the electric machine (motor), we use Ansys Maxwell 2D and 3D electromagnetic simulations. I’m kind of a visual person; I like to see things. Ansys Maxwell simulation software helps me to visualize and understand where certain boundaries or limitations are. If I need to present my ideas to the team, having some full-color simulation images is always a good idea.

We use Maxwell software to look at the output torque of the machine (the counter-electromotive force generated by the electric motor that enables its rotation) to understand how much torque we get for a certain input current.

We can also use it to look at loss. With the Porsche 99X Electric GEN3 Evo, we started early on with loss models as Maxwell software has a strong base you can build on, and it offers the possibility to increase our capabilities by doing additional postprocessing or adding some additional analytical calculations.

Ansys Mechanical software also helps us to optimize the rotor of the electric machine from a mechanical perspective. Typically, in motorsport we have a bit higher rotational speed than road cars to reach higher speeds on the track. The rotor is important, as it is the only moving part of the electromagnetic system responsible for generating the torque needed to drive the car at these speeds. Considering both electromagnetic and mechanical aspects early in the design process is really helpful for us.

Is there anything else that you factor into powertrain optimization besides the electric machine?

Mengoni: We have to always keep in mind that we have to work within the context of other components. Specifically, it’s the inverter, the component that transfers power from the battery to the electric motor. We use Ansys Q3D Extractor software to simulate the switching cell of the inverter. By using simulation, we can understand how to reduce switching loss for a given design or how a new design should look like to reduce inverter loss. There are also oscillations during switching, which we must consider in order to ensure safe operation of inverter and machine.

Simulating all switching actions that occur during a 45-minute race is not practical due to the large difference of time spans. Based on very detailed simulation, however, we can derive more general, easier-to-calculate models and use them again to calculate powertrain efficiency based on the inverter and the electric motor. And that gives us an idea of where to go.

So, adapting the car from rear-wheel drive to active all-wheel drive doesn’t make the challenge difficult — just different?

Mengoni: There are some differences. For us, it’s a similar approach with more input data we have to process because we have more scenarios. And yet there are big changes for the control engineers and the powertrain engineers at the track. They also have to consider the behavior of the car and the differences to the test bench.

For example, on the track you have to consider curbs and how to have good drivability with rear-wheel drive and all-wheel drive. I have a lot of respect for our race engineers and everyone at the track and in Weissach (Germany) because they can process the feedback from the driver and give them what they need.

The driver doesn’t feel if we have made a 0.1% efficiency gain because it’s a small change. The thing is, if we give the driver and the team a more efficient powertrain, we give them more options during a race. If you save more energy, it means you can maybe do a different (better) strategy.

You can push the car a bit more on race day. So this 0.1% efficiency gain we get from simulation, as a driver you may not feel it directly. But in the end, that little extra energy might be just enough to overtake someone when it counts.

Can you talk about the role that motorsport plays in road car development at Porsche?

Mengoni: There’s definitely the motivation at Porsche to embrace motorsport. It’s part of our brand identity. We have regular exchanges about projects other than Formula E with the road car engineers. They have, of course, slightly different requirements than we have. Not everyone should (be) or is driving their Porsche at the speeds we do with the Formula E car. Regardless, we have road cars with electric powertrains, so it just makes sense to talk to each other.

Both sides, road car and race car engineers, have good technical experience in very similar and very different areas. For example, acceleration and efficiency is a common topic, but others, like limitations due to either legal or racing series regulations, are very different.

Another difference is the development speed. For Formula E, we develop a new powertrain every two years, which is much shorter than the development cycles of a road car due to the smaller team and reduced number of regulations and processes. With the help of simulation, we can just try things and see if they work, and that is interesting for the road car developers. On the other side, we also benefit from their experience in common projects. I think it’s something both sides benefit from.

We hope that you enjoyed hearing from Mengoni as much as we did about the Porsche 99X Electric GEN3 Evo. We want to thank him for a great interview and encourage you to check out this story to learn how Ansys simulation drives powertrain development at Porsche Motorsport.