There is no shortage of news concerning the rapid increase in the electrification of transport (writes Wayne Ward). Perversely, while the Covid epidemic seemed to galvanise public opinion into supporting electrified transport, car manufacturers involved in motorsport were planning to quit the highest-profile electric race series.
Electric racing in its relative infancy, as it has yet not been able to capture the public’s admiration. At this point in time, batteries put a limit on speeds and endurance, and the noise from electric motors doesn’t give the same impression of speed and excitement as an IC engine.
However, a new, pure electric car from UK company McMurtry Automotive aims to do something about that. The McMurtry Speirling is a pure track car, and it is certain to provide proper race performance and excitement for a number of reasons, owing to some really good, detailed engineering and because it is free of the constraints of a rulebook.
Such rulebooks are contrived by people whose job it is to make rules and who, I like to think, try to think of sensible, cost-effective ways to make great leaps forward in performance and then writing rules to prevent such acts of engineering from being common sense.
Noise is usually in short supply in electrified motorsport. The McMurtry Speirling boasts an exciting design, fan-generated downforce and around 120 dB of noise (Images courtesy of McMurtry Automotive)
The McMurtry Speirling is a car absolutely unlike any other because of that lack of regulation. Of course, it has some features that we would recognise – an enclosed body, four wheels and so on – but the car is a case of less being more.
It is very small, short, low and narrow. It deceives you in that, without anything else for reference, it looks like a tall car, but that is not the case, its proportions only give that impression. It is quite a low car, but it is strikingly narrow and very short indeed. The shortness is exaggerated by having minimal overhangs at both ends.
It sits a driver in relative comfort, but it cocoons them quite tightly. It is clear that reducing frontal area was a key design target, so that whatever power is available provides the most benefit. The car has no wings, winglets, dive planes or the other accoutrements that we have become accustomed to seeing. The faster a conventional rac car travels, the more downforce it develops.
Without wings and suchlike, can this car expect to provide the levels of cornering excitement that its well-heeled customers will expect? According to McMurtry Automotive’s managing director Thomas Yates, the answer is a resounding “Yes”, and how the car is, as he describes it “astounding in terms of performance and range”.
Yates previously worked for Mercedes at its Brixworth powertrains HQ, and is therefore no stranger to working in an innovative culture. He says that, in terms of some of the main dimensions of the car, inspiration came from 1960s Formula One cars, those most single-minded and minimal of single-seat racers. Even against the Lotus 18, which Yates says provided some of that inspiration, this car looks short.
So, we have a car with an electric drivetrain and no obvious aero devices for providing downforce, yet the design target according to Yates is to provide “the performance and powertrain of tomorrow” through what he describes as “the application and reinvention of technology”.
Yates and McMurtry have their names on a rapidly increasing number of patents concerning their chosen technologies, one of which accounts for the astounding noise of this car.
When I take my bike to a track day, I sometimes approach the noise meter man (I’m not sexist, but it’s always a stern man) with a feeling of trepidation if the limit is around 110 dB. An electric car makes no discernible noise when it is not moving, but the McMurtry Speirling gives a very different impression. With the car motionless and the ‘throttle’ pedal pressed down, the sound could easily break my 110 dB track day limit.
The car can generate its maximum downforce at will and at any speed, and that is the source of the unique sound that it makes – Yates says the car can generate “more than 500 kg of downforce”. It can do so at any speed because its downforce is provided by an electric fan, which makes a great deal of noise.
Yates says the fan can use “more than 80 bhp”. While a parasitic fan might not sound like a very efficient idea, the car can shed all its downforce when it is not required. There are no wings to drag thorough the air at high speed, which also gives the car a very low drag coefficient.
The concept here is not only to have great downforce whenever required (regardless of speed) but as Yates explained, because the car only generates “downforce on demand” it does lead to increased efficiency and lower energy consumption.
Brabham is generally associated with ‘fan cars’, but there have been others. McMurtry’s version focuses not only on controlling the downforce as required, but in minimising the use of energy.
The effectiveness of the sealing arrangement is key to that. The work involved in maintaining a given level of pressure differential from the underside of the car (inside the fan seal) and its top side is proportional to the mass flow rate though the fan. With a more effective seal, the flow rate and energy use are minimised.
A number of McMurtry’s patents are concerned with the method and hardware for generating downforce. The company clearly sees the efficient application of a once-discarded technology as important enough to protect.
Given a limited battery capacity, the less energy used to generate downforce, the more laps can be driven before the battery is depleted. The battery in the Speirling has a capacity of just over 60 kWh.
Yates says the battery’s duration is “30 to 60 minutes at a really good pace”. That is hard to judge, but simulations based on the WLTP real-world automotive drive cycle have revealed that the McMurtry Speirling would have a range of 350 miles on public roads, which is exceptional and shows very low energy consumption per mile.
The battery is designed and assembled by McMurtry, and the packaging is a key element to the successful layout of the car. The battery is wrapped around the driver’s seat, and is optimised for centre of gravity in terms of height and front-rear weight distribution.
We might imagine that this means the battery is housed around the rear of the driver, but that is not the case. It is housed partly in the ‘sidepods’ of the car and under the driver’s legs, which are slightly elevated in a Formula One-style driving position.
Yates was notably coy about much of the powertrain, but was obviously pleased with the engineering of the battery. The way the battery is constructed and packaged, he says, is “the route to do batteries that are insanely good on power density and energy density”. Other than mentioning that the battery is, predictably, lithium-ion, that the output is over 800 V and that the cells are cylindrical rather than pouch style, he would not be drawn further.
Former Formula One driver Max Chilton looks pensive. With 1000 bhp, rear-wheel drive and controllable downforce, he has a lot to consider when driving this small, light racecar
800 V is something we see mentioned much more often. Higher voltage and lower current give greater efficiency for a given level of power, and also allow for faster charging.
The performance of the car is not surprising: Yates quotes the specific output as “1000 bhp per tonne” and the mass as “under a tonne”. Cars producing 1000 bhp/t are exceedingly rare, and 1000 bhp electric cars generally weigh very much more than a tonne.
To give a measure of the performance, the 0-186 mph (300 kph) time is less than 9 seconds, and the car has a quoted top speed of more than 200 mph. The downforce system is an important enabling technology in this respect, as the car is rear-wheel drive only.
High downforce can also be provided at low speed, so that the tyres are much less of a limit on acceleration. The Speirling is therefore much less traction-limited than a car of the same torque and mass but with speed-dependent downforce.
The drive is provided by two motors, which Yates would not discuss other than to note their 1000 bhp performance.
In Le Mans, Daytona and Formula One legend Derek Bell, former Formula One driver Max Chilton and British hillclimbing star Alex Summers, the company has a star line-up of development drivers to optimise the car. McMurtry aims for the Speirling to race in competitive motorsport in the future, but who would want to race against something so single-minded and with such huge performance? Perhaps a noisy one-make series with truly exciting cars and environmentally friendly credentials is what electrified motorsport needs.
