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Dual Motor Technology: Where’s the advantage?

As the Formula E competitors gathered to race in part one of their American showcase, China Racing turned up with a new logo slapped on the side of their cars; NextEV. They confirmed their new partnership after the Miami ePrix race and turned up to the next race in Long Beach with a new ‘NextEV-inspired’ livery, giving clues as to how major their involvement was going to be.

Earlier in the year, the Formula E organisers revealed the sport’s ‘development path’, including the technical rule changes for season two. In this announcement, it was confirmed that manufacturers would be permitted to develop their own powertrains from season two onwards. The components which can be developed from season two are the e-motor, inverter, gearbox and the cooling system.

Between the two American races, the confirmation of this new partnership between China Racing and NextEV also included information about next season’s plans. NextEV will be the team’s new powertrain supplier and were going to be providing ‘dual motor technology’ for season two, a one-up from this season’s single-motor car. A bold statement, you might think, and one that certainly sounds like the foundation of championship-dominating performance. When announcement came it was easy to think of the word ‘double’, but dual motor technology does not automatically mean double the performance.

It should be noted that Formula E will not yet be venturing into new territory with dual motor technology, as having two motors in one vehicle already exists in some electric sport cars. For example, Tesla have already used this to create an all-wheel drive car. This brings us nicely to the first problem with transferring the idea to Formula E: the very first rule under Formula E’s transmission regulations is that “only rear-wheel drive is allowed.” In addition to this regulation it would be a near-impossible task to send the drivetrain to the front wheels of a typical single-seater race car. So we have two motors for the rear axle only.

The next best thing you might think is have one motor on each of the rear wheels but unfortunately that’s ruled out for a number of reasons too. When referring to the rules, the main reason is that the “MGU(s) torque can only be transferred to the drive wheels through a single differential.” This is compounded by the fact that these are also geared vehicles, unlike many electric road cars. In addition to this, even if the manufacturers were able to transfer the power to the individual rear wheels, the advantages of doing so are negated by the rule not permitting ‘torque vectoring’, which is the technology to vary the torque to each independent wheel.

So the mechanical assembly of the car is likely to remain the same, but with all cars being limited to the same power outputs, is there an advantage to strapping two e-motors together to power the car? Despite the current motor (designed by McLaren) providing some of the best stats ever seen by an electric motor, it still weighs 26 kg (just over 4 stone). For motor racing, that’s a big chunk of weight to add, so the benefits had better be worth it. NextEV and China Racing have been talking about how the dual motor system will give better “efficiency” when it comes to both drive and regeneration modes, and this certainly need to be the case if it’s outweigh the benefits of a lighter car. Their aim for dual motor technology will be to minimise the losses which occur in electrical motor systems.

Essentially, don’t expect much in the way of a radical concept that is set to completely revolutionise the Formula E, as next year’s cars will most likely be a very similar layout to this year’s models, but that’s exactly what the FIA want to do. If you allow for very open rules, then you get a variety of results, and that’s where the sport’s competitiveness can be lost as the bigger-budget teams increase the gap to the rest of the field. However, that’s not to say that there aren’t benefits to running with two motors, it’ll just be harder to find them than it first appears. For now though, they’re the only powertrain manufacturer to have stated their intentions for next season, and that may just indicate how cautious others are to go down the same route.

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Luke Murphy

As an FIA-accredited motor sport journalist, degree-level Motorsport Engineer and amateur karter, Luke's passion for motor sport is evident. He is one of the editors at FormulaSpy and one of the longest-standing members of the team.

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