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09/07/2018
Formula-e in the eternal city!

Formula-E

 

The Rome Formula-E Grand Prix turned into a real festival bringing electric vehicles to the attention of a wide audience. But what can these exhaustless single-seaters teach us?

Nicodemo Angì

Rome EUR, the model district built during the 1930s to welcome the Universal Exposition of Rome in 1942, was the stage (and also the protagonist) of a very special Grand Prix. In mid-April, in fact, the EUR was transformed into the evocative stage for the ABB Formula-E championship, reserved for electrically-powered single-seat racing cars.

Motor racing, once a regular event on the streets of the capital, had been missing for a long time (too long).

 

A trip down memory lane

The first race won by Ferrari with a car of its own production was the Rome Grand Prix in 1947, on the Terme di Caracalla circuit. The last race, on the other hand, was held only four years later, in 1951, and during the 80s even Enzo Ferrari sponsored a return of motor racing on the roads of the capital city.

Unfortunately the idea ran aground due to environmental reasons, but Formula-E has the merit of having brought back world class racing to the city. The 2017/2018 championship has been hosted in cities such as Hong Kong, Marrakesh, Santiago de Chile, Mexico City, Punta del Este, Rome, Paris and Berlin. Next stage, July 10, Zurich followed by the grand final in New York with the final two Grand Prix. 

We have followed the stage in Rome and we can say that on April 14 we saw not only an exciting sporting event, which attracted huge crowds, including many who probably would never have seen a “classic” Grand Prix, but also a preview of how the automotive sector might change in the near future.

 

“Nasty” yet silent

Electric single-seaters make it possible, in fact, to race in city centres reachable, with great ease, by subway and it was a real pleasure to see a very competitive race, despite the unusual whirring sound, take place in the monumental backdrop of the EUR district.

The power developed by the batteries in race trim, limited by regulation,  is only 180kW/245 hp (200 kW in qualifying) but these racers appeared much more dynamic than one would think. The reason is obvious: these electric motors produce maximum torque at zero revs (or almost) therefore acceleration, for example coming out of a hairpin bend, is absolutely burning. In fact, going to 0 to 100 km/h takes place in about 3 seconds: not bad, considering that many family sedans have greater power and that a Formula 1 takes just under 2 seconds. The result is even more significant if we consider that a Formula-E has a minimum weight of 880 kg with the driver on board (changes are being studied to limit the disadvantage experienced by the heavier drivers).

So, when judging the dynamic qualities of the electric car we are thinking of buying, we should bear in mind that figures alone do not show the whole picture.

Furthermore, differently from more traditional vehicles, efficiency is rather significant even in competitive events.

 

Energy efficiency

The American Environmental Protection Agency (EPA) comparing the Energy efficiency of different vehicles, has long established that a gallon of petrol (3.78 litres) contains 33.7 kWh of energy . At this point it is quite easy to convert the consumption of electric vehicles into miles per gallon, just as we would do with fuel powered cars. Tesla’s new Model 3, for example, uses 26 kWh (combined city/highway cycle) to travel 100 miles while the efficient BMW 328d, equipped with a 2-litre turbo-diesel engine, uses 2.8 gallons per 100 miles, equal to 94,4 kWh. This means that the quick European sedan, manages an average mileage, measured by EPA, of 36 Miles Per Gallon (MPG) in a combined cycle (or 15.2 km/litre), while Tesla’s Model 3 scores a staggering 130 MPG. A petrol-fuelled Yaris manages 35 MPG while, still looking at Toyota, a Prius ECO scores the excellent value of 56 MPG.

And now, back to Formula E: the maximum energy supplied by the batteries is only 28 kWh hence cars are changed halfway through the race. Suppose that 95% of the available energy is used during the race, this would mean that 53.2 kWh were enough to cover the 59.64 km of the Rome Grand Prix: around 0.89 kWh per km.

Using EPA data we discover that a litre of petrol is equivalent to 8.91 kWh of energy and therefore these whirring Formula-Es managed 10 km/litre, an absolutely significant result that could be replicated even in production cars.

 

Reducing costs

Formula E is further characterized by standard components for all teams to reduce costs.

Monocoque and battery, for example, are the same for all, the first manufactured by Dallara and the second by Williams. The control unit, supplied by McLaren, is also standard, while the management software is developed by each team individually.

Price checks have been imposed also on the braking system: if, in fact, the materials used in making brake discs and pads are free, the callipers must be made of an aluminium alloy with an elasticity lower than a certain limit and the pistons must have a circular cross-section.

In addition, suspension arms must be made of steel, to limit costs and increase strength, as drivers regularly “swap paint” during the race, or “touch” walls and guard rails without major damages.

Any drive assist devices, whether braking or electric or hydraulic differentials are strictly forbidden as well as active suspensions. Moreover, working on shock absorbers, can be done only through tools in the pits and never with on-board digital devices.

 

Huge torque few gears

Even spoilers, aerodynamic fairings and air vents are regulated: front and rear "wings" must have a standard aerodynamic profile.

On the other hand, maximum freedom is allowed for the engines (the only limits are a maximum number of engines, 2, the prohibition of placing them in the wheels and the thickness of the electrical steel sheets, which must be greater than 5 hundredths of mm) and, as expected, designers have gone wild.

Magneti Marelli, one of Mahindra’s main suppliers, the team currently occupying fourth place in the Championship, has in fact designed and built a motor with two stators, each of which powered by three-phase electricity, and a single rotor. The greater torque developed by this configuration made it possible to eliminate the gearbox, replacing it with a gear reduction with a fixed ratio. If little is known about the transmission used by the team leading the championship (Techeetah, with Renault engine), what is known about the Audi-Schaeffler team is that it has a similar solution, which makes these cars unusually similar to the vast majority of production cars. Other teams use different gear strategies, though they are still few  as electric motors are able to reach 20,000 rpm and the torque curve is favourable.

 

Tires: a source of inspiration for production models

And now wheels: 18 inch steel monobloc wheels only. The rim width is 9 inches at the front and 11 at the rear while the tires, the same for every team are Michelins, size 245/40 R 18 at the front and 305/40 R 18 at the rear made to be used even in case of rain. The French manufacturer proudly speaks of its Pilot Sport EV, and confirms to have proposed to the FIA, and was later accepted, the use of 18" wheels as it is a fairly common size found also in production cars. Michelin is sure to acquire important data that will then be useful in mass production. We should point out that free practice, qualifying and the race are made with the same set of tires, which, as you will be able to read in another article on this issue of Pneurama, require low rolling friction and a great resistance to the huge torque delivered almost instantaneously by electric motors. Each tire is then equipped with an RFID tag that allows accurate traceability and each driver has 4 new tires available for each race along with a further 2 tires used in the previous race.

Finally, here is a list of the teams in this year’s championship: Audi, DS-Virgin, Jaguar, Mahindra, Renault, MS+AD Andretti (in cooperation with BMW), Dragon-Penske, Venturi, Techeetah and Nio. If we add that soon Porsche, Mercedes and BMW will join the formula and that new and more powerful cars are on the way, able to complete a race without having to change cars halfway through it, we can only start to grasp the full potential of this motorsport series.

 

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