Thirty-nine seconds and eight hundredths. This the new record on Goodwood’s 1.86 kilometer climb, marked by the futuristic McMurtry Speirling who broke the previous record held by Volkwsagen ID.R. The event offers an opportunity to deepen the engineering aspects of a car that demonstrates where the performance of the electric can go when conceived for exclusive sports use, without having to deal with the compromise between weight and range. The unique aesthetic of the Speirling, nicknamed the Batmobile by some, reflects its technical characteristics, which go well beyond the single double rear intake fan.
The real great strength of McMurtry’s creation is lightness, since with only 1000 kilograms of weight the Speirling borders on the typical mass of cars powered by a thermal engine. The conception of the car in anticipation of use on the track made it possible to remove the guarantee of high autonomy from the objectives. The designers have thus dimensioned the battery from over 800 V, limiting themselves to a capacity of 60 kWh, a lower value than others available on the market, with consequent weight savings. Nonetheless, the Volkswagen ID.R, the previous record holder at Goodwood, was equipped with an even smaller battery, of just 40 kWh, and further scaled down on the occasion of the first printed at the Festival of Speed. However, in spite of a more capable battery, the Speirling denotes an equally competitive weight, with 1000 kg against the 1100 kg including the driver of the ID.R.
However, the comparison between the batteries cannot lead to quantifying the weight in a measure directly proportional to the capacity. In fact, since 2018, the year of the competitive debut of the record-holder Volkswagen, the technology of accumulators has progressed considerably, in fact increasing the values of power density and energy. The relative lightness of the Speirling, however, is also attributable to other factors, above all the use of the double rear fan. The McMurtry hypercar mounts in fact a double system of air intake from the underbody, lowering the pressure under the bottom to generate downforce. Many associate this artifice with Brabham BT46B Formula 1 of 1978, but it is a solution that over the years has also found other uses. In the world of prototype sports, for example, the Chaparral 2J from 1970, which was equipped with a double rear fan transposed from an M109 Howitzer tank, a terribly fast car but whose lack of reliability undermined its success. In recent times, however, the Murray T50supercar also equipped with a bottom suction system.
For the first time, however, the double fan on the Speirling is powered directly from the electrical system. The system guarantees an aerodynamic load of 2000 kg when the car is stationary, offering a competitive advantage unmatched by traditional cars, which are forced to reach high speeds before they can rely on tangible downforce. In the case of McMurtry’s hypercar, on the other hand, the load level is more or less constant, considering that at a speed of 150 miles per hour, the equivalent of around 240 km / h, the maximum level of 2500 kg is registered. Being able to count on such a system for load generation, McMurtry engineers were able to design a single-seater with small dimensions and consequently with a limited mass, not having the need to have a large surface area of the bottom to generate downforce. In fact, the Speirling barely measures 1.7 meters wideagainst 2.3 of the ID.R, while in length there are 3.7 meters compared to the 5.2 meters of the Volkswagen.
In the final balance, therefore, the double rear fan made it possible to downsize and lighten the car without sacrificing the exceptional aerodynamic load values. The search for lightness also turns out to be recursive in the design phase, since less weight translates into less mechanical stress, with consequent lightening of the structural components. The combination of load and low weight allow the Speirling to achieve lateral accelerations greater than 3g. These values might appear not very impressive when compared to the over 5g of Formula 1, but we must consider the over 200 kg of extra weight and the use of tires with a tread of 210 mm at the front and 240 mm at the rear, against 305 and 405 mm of the Pirelli in use in F1.
The installation of a high-performance powertrain was nothing more than the finalization of the dynamic qualities already impressed on Speirling. The single-seater is equipped with a double engine on the rear axle, thus giving up the opportunity of an all-wheel drive, but McMurtry did not specify whether the coupling with the rear wheels uses a mechanical differential or if the car instead resorts to torque control. vectoring. The total power is 1000 horsepower, against the 680 horsepower of the ID.R, outlining a power-to-weight ratio around the unit. The maximum speed is about 240 km / h, a value limited by the use of a time trial gear ratio, with the possibility therefore of raising the speed tip. The most impressive of all, however, is the sprint from 0 to 100 km / h, credited in 1.5 seconds, taking advantage of the readiness of the electric torque, the relative lightness of the car and the availability of aerodynamic load and therefore grip already at low speeds. To top it all off, the suspensions are equipped with an active ground clearance control system.
Speirling demonstrates what goals an electric car can achieve when it is not limited by the need for a high range and is rather conceived as a function of ultimate performance. However, the intrinsic limit in electric technology related to the weight of the batteries remains, a factor that is never negligible even in extreme design works such as that carried out by McMurtry. For example, the Viritech Apricale, hydrogen fuel-cell hypercar with a battery of minimum dimensions, for a power of 1100 horsepower and a weight of just 1000 kg, in line with the Speirling even though it was born as a two-seater for road use. In a climate of constant revolution in the sector, it therefore arises spontaneously to ask how long the leadership of McMurtry will resist, with the bar destined to move higher and higher.
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