We talk about it constantly during the races: who’s got the most efficient car? Who’s managing most efficiently? It’s not just about bullet journalling your way around the circuit though, clearly.
In electric vehicles, efficiency is about how you can get the most out of the power you have. From a driver’s perspective, that means making savings where you can, around a lap. Alexander Sims, driving for Mahindra this year, told us why setup plays a key part in that, “Efficiency in the races is really just lap time versus total energy consumption per lap. I would say the the bulk of efficiency over a lap is actually, from what we can control when we’re at the track, anyway, is actually in the corners.
“So if you can have a really good car balance and predictable car that you can brake late with and carry good corner speed, it means that you gain the lap time there and then you can coast early and regen early and you can conserve your energy on the straights.”
That’s why sometimes teams have have seemed super efficient on one track might not be able to extract the same efficiency at a different one, if they can’t work out a set up that the drivers are comfortable with. Alex explained, “There’s obviously a decent amount of efficiency tied up in the fundamentals of the powertrain, the gear box, inverter – but electric motors anyway, there will be efficiency differences between teams, but they’re all damn efficient. So you’re talking about, I don’t know, the 0.1 percents, whereas if you have a car that’s too oversteer-y or too understeer-y, you’re going to be losing half a percent of lap time and therefore a big chunk of efficiency each lap.”
That can then get further effected in the race, if you have an incident. It’s not just damaged aero (of which Formula E cars have, honestly, very little – especially compared to Formula One) but if something’s throwing a driver off, they can lose meaningful amounts of energy.
“The body work is very solid but if you touch another car with a bit of steering on,” by which Alex means ‘in a corner’ – where they tend to collide.”You’re very likely to to bend the steering arm or something and then your car balance goes out the window. But in terms of efficiency, the biggest thing really is being able to have a well-balanced, predictable car for the driver to feel confident to just carry that extra kilometre an hour through some corners and then suddenly that adds up to a tenth [of a second] or two gained in lap time.”
Of course, efficiency isn’t down to the driver alone. Mahindra’s performance director Josef Holden explained that it goes way beyond one or two variables, into the entire structure of the team. “[Efficiency] is the optimal use of resource at the right time. That can extend to: do you have the right people doing the right roles, with the right capabilities? Where are there knowledge gaps? And that’s across the racing sphere, across the field itself.
“It goes through to: have you designed your power unit so that it’s offering peak efficiency in the correct motor speed range, so that you know, from a qualifying and race perspective, that’s where you’re delivering most performance? It’s: are you operating the right thermal range to ensure that?
Efficiency isn’t just what you’re doing in. single moment, either – as with anything in Formula E, it’s about finding performance in a sustainable way, where the car can keep delivering at that level. “Yes, based on battery technology, it’s an electrochemical reaction that things speed up when they get hotter but you also degrade their performance over time and we want to ensure that, from a thermal management perspective, we have a very small window of operations. So we don’t want to be artificially inducing a complete full on performance for two laps, but at the expense of the next 30.
“So I think across the sphere efficiency is really just the optimal use of resource. Whether that’s time, money, people or physics on the racetrack.”
In terms of measuring that, when you’re watching a race: efficiency is visible in how much a driver or team is struggling. Sometimes they’ll be able to make a situation work but are clearly having to fight to hold on to a position or expend excess energy on an overtake. Sometimes they’ll be unable to regenerate energy and be forced to slow down because their battery has reached too critical a temperature; the trick is to manage it all when it needs to be.
Which is what makes Formula E so tactically complex; so when we’re talking about efficiency, it’s about the way a team was able to set up a car – and the way they and their drivers can then best use that, strategically. Like saving tyres in Formula One, efficiency in Formula E is about finding your best performance window for the situation you’re in.