McMurtry Spéirling

The McMurtry Spéirling is a record breaking electric single-seat prototype car which was first presented at the Goodwood Festival of Speed in 2021. The car is developed by McMurtry Automotive, a British registered startup founded on 2 June 2016 by Sir David McMurtry (co-founder and executive chairman of Renishaw plc). "Spéirling" is Irish for "thunderstorm".

History
According to McMurtry, the motivation behind the car was to challenge the industry trend of increasingly heavier vehicles and, by using first principles design, create a lightweight electric drivers car. The prototype car is the first step to demonstrate what customers will experience on road and track. It is not currently in a racing series but is built to satisfy relevant motorsport safety requirements, with crash structures and a carbon-fibre monocoque chassis with integral rollover protection. Its unique performance differentiator is the fan powered downforce system, giving 2000 kg of downforce from 0 mph.

The car was first presented at the Goodwood Festival of Speed on 8–11 July 2021, and driven by Derek Bell. The car had been developed in secrecy over three years.

On 26 June 2022, the Spéirling achieved a new Goodwood Festival of Speed hill climb record, completing the 1.87 km course in 39.08 seconds with McMurtry test driver Max Chilton behind the wheel.

In December 2022, it set the following times verified by independent GPS timing without rollout by Mat Watson from carwow on Silverstone:


 * 0-60 mph in 1.4s
 * 0-100 mph in 2.6s
 * 0-145 mph in 4.9s
 * 1/4 mile in 7.9s at 177 mph

When considering the $1/4$ mile time, the car had a 155 mph top speed for roughly the last 3 seconds of the run. The car also ran on bespoke drag slicks and was not a production car model.

Specifications
Manufacturer specifications Spéirling PURE:
 * Peak power output: 1000 bph (745kW)
 * Top speed: 298.0 km/h
 * 0-60 mph: 1.40 sec
 * 1/4 mile: 7.97 sec
 * Weight: 900 Kg
 * Battery capacity: 100 kWh
 * Rear wheel drive

Estimated driving time on a race track at a GT4 pace is about 25 minutes.

The car has rear-wheel drive using two electric motors placed inside a specially designed "e-axle", and uses carbon brakes. The monocoque has room for a driver 150 to 200 cm tall. The battery is integrated into a separate safety cell inside the monocoque.

Active downforce
A special design aspect of the car is its active downforce system without the use of large splitters or wings, by means of twin fans which provide an extra 2000 kg of downforce from a standstill. This allows the car to corner at a G-force of more than 3g. When the fans are at full speed, they emit about 120 dB of noise, comparable to that of a jet engine at full thrust.

The use of fans powered by separate motors to provide downforce was first conceived of by Jim Hall for the Chaparral 2J, a Can-Am car he designed, constructed and raced in 1970. It was banned at the end of the 1970 Can-Am series. A downforce fan system was also used in the Brabham BT46B Formula One car, which was designed by Gordon Murray. The BT46B raced at the beginning of the 1978 season to great effect before a rule change was made under pressure from other race teams, resulting in a ban on movable aerodynamic surfaces.

Tyres
The tyre width is 210 mm on the front and 240 mm on the rear, both on 19 inch rims. This is modest for a supercar and is comparable with regular road cars which tend to have tyre widths from 195 to 205 mm.

Comparable electric cars

 * Volkswagen I.D. R
 * Rimac Nevera
 * NIO EP9
 * Aspark Owl
 * Pininfarina Battista

Other fan cars

 * Gordon Murray Automotive T.50
 * Brabham BT46
 * Chaparral 2J