IGNITION
Gordon Murray tells evo how the T.50 supercar’s advanced aerodynamics will translate from paper to the real world
Gordon Murray on the T.50, Porsche’s new 718 GTS and the latest concepts from Mercedes-Benz, Hyundai and even Sony at the CES
GORDON MURRAY HAS PICKED UP THE pens. evo is about to get a one-to-one lesson in the aerodynamic principles behind the new T.50. As I nurse my cup of tea in the GMD boardroom, the man himself begins talking and I have to try hard to suppress a wry smile at the surreality of the moment. Days like this don't come around too often.
Gordon Murray Automotive (GMA) has chosen to go public with the next stage of the T.50's development, and has released a rendering of the car, too (see over the page), which clearly shows the same clean surfaces and aggressively sawn-off rear end that characterised the McLaren F1. Murray has been able to achieve this aesthetic via the car's unique underbody aerodynamics, supplemented by a 400mm vertical fan that dominates the rear of the car. It's groundbreaking stuff, as I'm about to hear.
‘I suppose it starts with ground effect, with the Brabham BT44 in 1974,' begins Murray. ‘The whole concept of that car was an upturned saucer, the triangular shape, and that was to move the [air] stagnation point down and try and force more air over the top with only a little going under. We realised, even without wind tunnels, that the air that went under produced lift, basically. But I took it a step further, and when we tested it out at Kyalami before the season began, I thought “that's working” because we could run less conventional front
and rear wings than the other teams, because we weren't generating the lift. It was a crude form of ground effect – reducing the lift rather than producing downforce.'
Having talked through the infamous BT46B ‘fan car', Murray brings the story up to date: ‘When I did the McLaren F1, I didn't want too much downforce at top speed. We calculated the F1 would do 378kmph, and I knew if we started at 160kmph with quite a lot of downforce, as it goes up with the square of the speed by the time we were at 378kmph it would be really difficult to manage, and that's the problem with any car with passive aero. You use up all the suspension travel, and the car becomes unstable and too stiff.
‘There's two ways around it: I wanted the car to be a GT, so I chose the first route, which is not to start with too much downforce, just enough to make the car stable, so at 386 there's a lot more but still manageable. Or, you make the car unbelievably stiff on the spring rates, and therefore you have an uncomfortable car anyway, short of having hydraulic lifts like Bugatti where you keep lifting the car as you go faster, which is complex and heavy, and doesn't register on my scale of interest. When I did the F1, it was about using the fan in a much more sophisticated way. It's an aircraft thing. They've had boundary layer control for a long time.'
The pen continues squeaking its way across the white board. ‘You have to be very gentle with the slope of the diffuser otherwise the air separates; boundary air is a wedge of slowmoving air that builds up, getting thicker and thicker. If you get the diffuser too steep, the air separates and it won't follow it. You're stuck. With the F1, I thought about what if you had a section that is much steeper, and of course the air will separate, but I had a slot with two small fans, in the flanks of the car, cooling the DC converter, the engine bay, and were also ducted to this point. When they were switched on, it cleared the air away and we got a bit more downforce. Enough to show up on the wind tunnel. I thought: “What control you could have over the aero [with this system]. You wouldn't be a slave to car speed anymore. But you'd need
I WANTED TO EXPERIMENT, BUT ALSO GET BACK TO A BEAUTIFUL CAR
a much bigger fan, though.” That's when the idea was born.
‘So when we decided to do the T.50, I thought, “I'm going to have a go at making that work big time,” and it's worked even better than we ever imagined. It's opened up so many possibilities to control the airflow actively, because it's an electric motor [the F1's was run off the engine]. Now we have a 48V generator on the front of the crank, a small 48V motor driving the fan, and we can do whatever we like with it: spool it up at different speeds, run it at different speeds. It interacts with the top surface, the side surface, the bottom surface, all the time.'
There are various modes to the aero system – six in total, including one test mode. Two are automatic: the Auto setting, where the ducting, fan and rear spoiler work, well, as you might imagine, and the Braking mode, where the spoilers are deployed fully and the fan works at high speed, increasing downforce by 100 per cent and reducing the braking distance from 240kmph to zero by 10 metres. In addition, there is a High Downforce mode, which provides up to 30 per cent more of the invisible force, and perhaps most interesting of all, the Streamline and Vmax modes.
‘In High Downforce or Braking mode, we force the air to follow this very steep diffuser, and the wing pops up as well to further help pull the air through. In Streamline mode the diffuser stalls [with the ducts closed] and the wing goes to -10 degrees to reduce the vortex. The fan goes to max speed to fill the eflux [the middle area or wake directly behind the car's tail] with dirty air and make, in effect, a [invisible] longtail. We suck air from the side flanks so the rear bodywork can be tucked in nicely [for aesthetics], but the air can't follow them normally, but we're getting a big vortex off the side. Makes the car virtually a metre longer.'
The T.50 can therefore do without the slabby flat sides aft of the rear wheels commonplace on racing sportscars. This ten per cent drag reduction will be available at the flick of a switch. At high speed, Murray says you should feel the difference instantly, with a constant throttle, which sounds quite surreal. Vmax mode also includes a 30bhp boost from the electric generator (along with ram air-effect induction), thereby taking peak power to a fulsome 700bhp for three minutes at a time.
‘I wanted to experiment with aerodynamics, but I was also desperate to get back to a beautiful car again, with good proportions. We've managed to make the car even cleaner than the F1. I've managed to actually reduce the holes and ducts and swoops.'
To develop this aero package, GMA has teamed with Racing Point F1 based at Silverstone. ‘I've known Lawrence Stroll [the team's owner] for a while, and we really get on very well. I had to find a team that wasn't aligned with road cars and I'm always a little nervous of consultancies generally. [His polite response to my ‘why not Williams?' question.] They're switching wind tunnels, so we've not only got a wind tunnel that's free whenever we want it, which is almost impossible with an F1 team, but we get access to their engineers and aerodynamicists as well.'
As we meet, the CFD (Computational Fluid Dynamics) on the car has been completed, and the detail design work with a 40 per cent scale model in the tunnel on a rolling road is about to begin. ‘Our aero team will continue working on it, but will integrate with Racing Point, because what we don't have is any current knowledge of working in large-scale wind tunnels. We're doing full OEM vehicle development, which is about 22 months of work. Not just homologation work, but full durability, corrosion, hot weather and cold weather, just to make sure we deliver a reliable motor car.' You won't find that on many multi-million pound hypercars from new, niche manufacturers.
If the aero is fascinating, then the other main area of interest, both for Gordon and us, is with the T.50's naturally aspirated 4-litre engine. Remember, this is a bespoke motor from Cosworth, commissioned by GMA, that is claimed to rev to an unbelievable 12,100rpm. ‘We've been running two levels of engine so far. The engine was fundamentally designed at the beginning of 2019 and signed off, and as we speak they've already done three months' work on their generic 1.6-litre engine on an early study on combustion. We're not anything to do with the Valkyrie engine – this is a next generation. We don't share any componentry or anything. We're a lot smaller and a lot lighter. They're quite different engines, but of course, we benefit from all the background knowledge they've acquired.'
Full speed ahead, Gordon.