Despite an ever-evolving game of supercar one-upmanship, the car that has caused arguably the greatest stir of 2020 – if not the past decade – isn’t the most powerful, or even the fastest, but it is certainly the most focused: Gordon Murray’s T.50.
His stated goal is a simple one: to create the greatest driver’s car. Every element of the experience, from the steering feel to the gearshift, the weight of each control to the engine note, has been honed with this target in mind. In Murray’s words, “I have absolutely no interest in chasing records for top speed or acceleration. Our focus is on delivering the purest, most rewarding driving experience of any supercar ever built.”
But what engine for a car whose creator is looking to bookend the supercar era, the last truly analog driver’s car? As Murray put it to Engine + Powertrain Technology International, “I wanted a V12 from day one. For me this is the most characterful and evocative engine layout and it fits our goal of producing the ultimate driver’s car.” Among the inspiration behind this call, he says, is the engine that powered such legendary machines as the 250 and 365 GTB/4 Daytona: “I am a great fan of the 1960s Ferrari 3-liter V12 by Colombo.”
However, the 3.9-liter, 65° V12 that will grace the rear of the T.50 is far removed from the V12s of old. Developed and manufactured by UK-based Cosworth Engineering and drawing on the company’s motorsport heritage, it redlines at 12,100rpm and has a peak power of 672ps, making it a truly 21st century engine.
According to Bruce Wood, managing director of powertrain at Cosworth, there was no traditional tender process for the engine, more a series of informal conversations with Murray and his team, following which the project got underway in mid-2018. Murray admits that there were initially three companies considered. However, “Cosworth was the obvious choice,” not least because at the time of the meetings it was in the process of delivering the engine for the Aston Martin Valkyrie, a car with a different ethos, but also requiring a very high-revving, naturally aspirated V12. At 6.5 liters it is of larger capacity than the T.50’s, and has hybrid assistance, but its development made Cosworth unique.
There wasn’t a hard and fast engineering brief either. Murray had settled on a capacity of around 3.9 liters, but, notes Wood, “Gordon has commented many times that it was not just about chasing numbers, and that approach rather defines the car, or at least our role in it. It wasn’t a case of, here’s a table of numbers that everyone has to achieve, it was a more analog process than that, more emotion-driven than just stark numbers.”
For example, he highlights, “We were clear we wanted to put a significant distance in terms of engine speed to anything else out there, which is where the 12,000rpm number came from. That meant power was never going to be a problem, because if you’ve got four liters running at 12,000rpm, you’re going to have enough power.”
It should be noted that the power-to-weight target Murray initially set for the car was 610ps/ton, which it comfortably exceeds.
Factors such as the V-angle and crank height of the engine were driven by the packaging demands of the chassis. The placement of the exhaust, says Wood, consisting as it does of six individual primaries on either side, pushed the design toward the narrowest possible bank angle, but, “There’s also an awful lot to fit in the center of the vee.” The 65° angle was the ideal compromise, and a crank center height of 85mm met the designer’s desires in terms of CoG.
Murray wanted only the intake plenums and exhaust system to be visible from above when the two butterfly-hinged engine covers are open, highlighting attention to the aesthetic as well as engineering detail as a recurring theme running through his work. “Sometimes, it doesn’t seem to matter what an engine looks like,” muses Wood, who nearly pursued a career in industrial design. “But for Cosworth this has always been very important. I’m a firm believer that good engineering also looks great. It was nice to have that opportunity where the appearance mattered as much to Gordon as it did to us.”
To achieve the clean looks, there are no belt-driven ancillaries, with drive for the various pumps taken directly from the block. “It actually worked out quite nicely for us,” says Wood. “Sometimes you end up with drives at both ends of the engine: the cam drive at the rear end, to keep its noise away from the tub, and the auxiliaries at the front, to accommodate underfloor tunnels. That’s very much the race car style, but [due to the use of a fan]the T.50 has small tunnels, so we could put the pumps at the back of the engine as well and only use one drive.” Not only did this solution meet the aesthetic requirements, it also reduced the overall engine length and reduced weight.
Murray confirms that all aesthetic targets were met. “I was after engineering art and Cosworth delivered.”
To a company such as Cosworth, which is responsible for the first 20,000rpm Formula 1 engine, meeting the 12,000rpm target was within its comfort zone in terms of the reciprocating components. Elements such as bearings are of course sized to meet the running life requirements (6,000km oil changes and an 80,000km service life) and parts like the titanium connecting rods are straight out of the motorsport playbook.
The addition of a Cosworth 48V integrated starter/generator (ISG) had to be considered when it came to the crankshaft and block design, contributing as it does significant inertia at the nose of the crank. “That had to be factored in right from the very start; the cranktrain dynamics were all modeled with that in place. The system uses a two-stage gearbox and there is a compliant element within that which is tuned to prevent the inertia doing anything nasty,” explains Wood.
The pistons are particularly noteworthy, being forged from a metal matrix composite rather than aluminum alloy. “Due to engine speed and power density, and because it is a road engine with quite a heavy ring pack, we were right on the limit of what we could achieve with a monolithic material,” says Wood. Cosworth has been developing MMC pistons for several years with materials partner Materion, and is comfortable with their use. “It gives a bit of design freedom,” Wood adds, “although we make the pistons and do you get through cutting tools!”
The MMC pistons run in plasma-coated bores, a process that Cosworth completes in-house, having been using linerless blocks since its CA F1 engine of 2006. “We used it in race engines,” says Wood, “and then more in road engines, particularly the high-performance ones.”
The engine runs conventional valve springs and, given its operating RPM, optimization of these and the rest of the valvetrain was vital to attaining reliability. “If you’re going to have a failure, clearly the valvetrain is the most obvious place,” notes Wood.
Of course, Cosworth has gone to great lengths to prevent this being an issue. Close attention has been paid to the cam profiles, particularly the transition between the ramps, while the valve springs – sourced from a long-time supplier in Japan – are made with triple vacuum remelted steel. “It’s all about getting the parts as light as humanly possible and then getting the springs right,” Wood summarizes. “They will always fail from an inclusion, they don’t just fail randomly, so you need that wire to be as clean as possible to prevent that. Then you spend a great deal of time finessing the cam profile. That was all a big, big piece of work to get right.”
The result of Cosworth’s efforts is truly impressive; a fully emissions-compliant, naturally aspirated engine that can rev to the stratosphere and packs just shy of 172ps/liter. The first GMA V12 engine fired up on the dyno in July 2020, and from now until customer car deliveries begin in 2022 Cosworth is focusing its attentions on fine-tuning the calibration, to ensure Murray’s demands for impeccable driveability are met.
Wood concludes, “We’ve got a team of seven calibration engineers working on it and the very first mule car is dedicated to calibration work. Even though we’ve ticked the box to say the combustion system can deliver on emissions, it’s still a two-year job to finesse everything to perfection.”