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- BESPOKE XTRAC ‘H-PATTERN’ TRANSMISSION IS LIGHT, COMPACT AND DELIVERS THE BEST SHIFT ACTION OF ANY ROAD CAR
21.07.2020.- Ahead of the global premiere of the T.50 supercar on 4 August (17:00 BST), Gordon Murray Automotive has confirmed full details of the bespoke Cosworth GMA V12 engine that will power the new model.
The 3.9-litre powerplant will be the highest revving, fastest responding, most power dense, and lightest naturally aspirated V12 road car engine ever. Meticulously designed and engineered, the powerplant combines the immense experience of Cosworth and Murray to be the most engaging, characterful and driver-focused V12 engine ever produced.
Brief: A Formula One engine for the road
Professor Gordon Murray CBE: “More than half of any truly great driving experience is delivered by the engine, so right from the start I set the highest possible benchmark – to create the world’s greatest naturally-aspirated V12.
“To be truly remarkable, an engine needs to have the right character; highly-responsive, an amazing sound, engaging torque delivery, free-revving, and it has to be naturally aspirated. For all those reasons, the engine in the T.50 was never going to be anything other than a V12.”
A key part of the brief was to keep the capacity of the T.50’s V12 as small as possible. The original inspiration for the engine stemmed from the 3.3-litre V12 powering the legendary Ferrari 250 GTO – small capacity, characterful and powerful. With a clear view on the required acceleration and torque, and the goal of a sub-1,000kg total vehicle weight, Cosworth proposed the capacity could be just 3.9-litres while still achieving supercar performance.
Murray’s brief was clear – the engine had to be light. It had to have the fastest response time of any engine ever built for the road, aping the targets set for his illustrious McLaren F1. It had to be high revving too, and for this characteristic Murray benchmarked the record set with his Light Car Company ‘Rocket’, which revved to 11,500rpm. And to top it off, it had to be characterful, sound superb, and look good – a clean design with no coverings or belt-driven ancillaries.
Not only does the T.50’s V12 promise screaming high-end power, it is also tractable for everyday driving. The maximum torque figure of 467Nm is produced at 9,000rpm, but key to ensuring day-to-day driveability is that 71% of the engine’s torque will be produced from as low as 2,500rpm.
In its most extreme aerodynamic setting – Vmax Mode – the T.50 is optimised for outright performance. Here, while gaining around 50PS from the car’s 48-volt integrated starter-generator, the car combines motorsport slipstream technology and ram air induction to boost performance even further.
Experience: Murray + Cosworth = ultimate motorsport and supercar collaboration
Having started his career as an engine designer, Professor Murray was keen to have a significant influence over the design of the T.50 engine. The powertrain also draws on Murray’s learnings from Formula One racing and his creation of the McLaren F1.
Murray: “Ultra-light components, intelligent packaging and a really fast engine response all come directly from my 20 years’ experience in Formula One. It also informs how everything is driven – the T.50 has no belts, it’s all gear-driven – a direct inheritance from the pinnacle of motorsport”.
Layering Murray’s depth of knowledge with Cosworth’s immense expertise in high-performance engines is what takes the T.50 engine to another level. The name Cosworth is synonymous with racing – from Formula One, to rally, to IndyCar – as well as production of some of the most admired supercar engines in the world.
Bruce Wood, Cosworth Managing Director: “The criteria and benchmarks set by Gordon for the T.50 engine comprised one of the toughest engine briefs we’ve ever taken on. It pushes the boundaries in every direction and it is a genuine thrill for everyone at Cosworth to be part of what will surely become as fabled a vehicle as Gordon’s McLaren F1 before it.
“The programme has taken Cosworth to new heights and, although only time will tell, it already feels like the GMA V12 has the potential to be one of the most iconic engines of all time.”
In devising his brief for the T.50 engine, Murray drew on his experience working with the 3.5-litre Honda RA121E V12 engine that powered the McLaren MP4/6 Formula One cars in the early nineties. According to Murray, this engine was the peak of the Formula One V12 powerplants in terms of its performance, balance and weight.
The T.50 powertrain also draws inspiration from the BMW S70/2 V12 developed for Murray’s highly revered McLaren F1, which to many remains the ultimate supercar engine. But for Murray there were improvements that could be made.
Murray: “Above all else, I wanted it to look clean like the BMW S70/2 engine, which had no carbon or plastic covers. It was just inlet trumpets, cam covers, exhaust block and heads, and a few belt-driven ancillaries that I managed to squeeze out of sight. In designing the T.50 V12, I wanted it to be the antidote to the modern supercar where you can’t see the engine beneath carbon covers.”
Even today, the F1 is considered to be one of the finest driver’s cars money can buy – but Murray always felt that the S70/2 engine could have been improved. The BMW unit is a much lower revving engine, meaning that for Murray, just as the sound began to build, the next gearchange cut the experience short.
Creation: a 100% bespoke V12 that may never be surpassed
Murray: “I started my career as an engine designer, so conceiving and specifying the 100% bespoke 3.9-litre V12 for the T.50 was such a joy. Having a blank sheet of paper and setting out to create the world’s best, highest-revving, most beautifully crafted, amazing sounding engine is something I’ve been waiting to do for years!”
The highest-revving, most responsive naturally aspirated engine ever
The record for highest-revving engine was previously held by another of Gordon Murray’s creations – the 11,500rpm Light Car Company’s ‘Rocket’. This record will be beaten by the T.50 V12.
Beyond the record-setting and the totally-unique experience of driving a car that revs this high, the logic behind the 12,100rpm is to maximise driver engagement with, and appreciation of, the raw power available as revs increase.
The T.50 engine will deliver maximum power (663PS) at 11,500rpm. But driver enjoyment won’t kick in only at the far end of the rev range. This engine will also be the most responsive naturally aspirated road-car engine ever produced. Measured in revolutions gained per second, the T.50 will achieve mind-boggling responsiveness, picking up at 28,400 revs per second (the F1 engine’s equivalent is around 10,000 revs per second). To put the T.50 figure into context, this means that its V12 can rev from idle to its 12,100rpm redline in 0.3 of a second. Another figure that sets a new benchmark and is unlikely to ever be surpassed with a road car.
The most power-dense naturally aspirated engine ever
The T.50 engine produces the highest power density of any naturally aspirated road car engine ever made – 166PS-per-litre. This record, coupled with the lightness of the unit, places this engine right at the pinnacle of naturally-aspirated powertrain development.
The lightest road-going V12 ever
The T.50 V12 had to be light, to align with Murray’s ethos for the whole car. To achieve the lowest weight possible the block in the T.50 is made from a high-strength aluminium alloy, the crankshaft is made from steel and weighs only 13 kilograms, and the connecting rods and valves are made from titanium – as is the clutch housing. This all contributed to engine weight of just 178kg – yet another road-car record.
Murray: “Good design throughout kept engine weight low, while our refusal to cut corners in terms of quality, packaging, layout, and of course performance ensured we surpassed all of our goals.”
The best V12 sound ever
Delivering on a key element of the brief, the naturally-aspirated powerplant in the T.50 promises to be one of the best sounding road car engines ever made.
Part of the aural enjoyment will be created by the car’s screaming redline, but the team behind the T.50 have also found additional ways to ensure the sound of the engine delivers maximum driver enjoyment. The T.50 features Direct Path Induction Sound – a system pioneered on the McLaren F1 and refined on the T.50 to channel the sound of the raucous V12 into the cabin.
The cold-air ram induction intake sits immediately above the driver’s head, and is crafted – with varying thicknesses of carbon fibre in the roof that act as a loudspeaker – to amplify engine sound in the cabin. The beauty of the system is that it is actuated by throttle angle and not revs, this means the T.50 is quiet and refined on part throttle and grows louder as the driver pushes through half-throttle and beyond.
Murray: “You can never get a great sound from a turbocharged engine. The T.50 engine sound is going to be phenomenal. The intoxicating growl that drivers love is introduced as the throttle angle increases, the sound intensifies as the induction sound kicks in, then as you push towards the upper end of the rev range the V12 will sing like nothing else on the road.”
Engineering-in optimal driver enjoyment
The T.50’s engine is semi-structural, providing much of the rigidity and weight saving found in a race car, without compromising driver comfort and cabin refinement. The Gordon Murray Automotive team opted for a semi-structural engine to reap the rewards of weight saving and stiffness while avoiding the NVH downsides of fully-structural units, which struggle with cabin noise and ride-comfort.
In the T.50, the suspension wishbones are connected to the gearbox casing, which manages the forces associated with braking, accelerative reaction and lateral cornering forces. Lateral movement of the engine is limited by two rubber-mounted trapezoidal links from the gearbox. Looking at the rear of the car, these links meet at the ground plane, forming a triangle and adding stiffness while limiting any lateral movement. Meanwhile, fore and aft movement of the engine is kept in check by snubber bushings on the engine mountings that allow the degree of engine movement to be tuned during maximum acceleration and braking.
Low centre of gravity
The size, weight and well-considered positioning of the T.50’s engine all play a key role delivering the car’s overall low centre of gravity. Compact dimensions were critical. Murray’s aim was to better the F1’s 125mm crank height, a feat more than achieved with the new supercar’s crank, sitting just 85mm from the bottom of the engine. This is largely thanks to Cosworth’s innovative design, which scavenges oil using windage to ensure that the crank sits as close to the sump line as possible.
This improves the vehicle dynamics in a few key areas. The low centre of gravity means less pitch during cornering and braking, less squat and dive and better transient handling. The overall effect cannot be overestimated for the T.50’s vehicle dynamics.
Engineering art: The beauty of simplicity
The average modern supercar is festooned with plastic and carbon fibre covers – the T.50 is not. In many ways the car serves as the antithesis to the modern supercar, presenting a clean and contemporary celebration of the engine, evocative of the stripped-back approach evident with 1960s performance cars.
The T.50’s engine bay is designed to present the engine in all its glory. Housed beneath duel ‘gullwing’ openings, which both pivot from the car’s central spine, the engine sits proudly without covers to focus on the raw beauty of the V12.
Inspired by race car engines, the Cosworth GMA V12 uses gear-driven ancillaries for lightness, with the added benefit of a clean and uncluttered engine bay, devoid of unsightly belts. All of the ancillaries are carefully positioned out of sight leaving the block heads, primary exhaust manifolds and inlet trumpets centre stage.
Murray: “Every component on this car is a piece of engineering art, and the engine is no exception. I wanted the engine to look like a modern interpretation of a 1960s V12. If it wasn’t the beating heart of the T.50 it would make a fabulous, sculptural modern-art installation.”
The world’s best gearchange – six-speed close-ratio transmission
Created by British transmission experts Xtrac, the short-shifting six-speed manual gearbox in the T.50 is staggeringly lightweight. Weighing just 80.5kg, the bespoke unit was created to meet the brief to offer ‘the best gearchange in the world’ – for maximum driver enjoyment.
Murray: “Maximising the driver’s connection with the T.50 was central to our decision-making. So, matching the V12 engine to an exquisite short-shifting manual gearbox was an easy decision to make.”
Brief: Super-light, highly-compact, zero compromise on shift quality
As with the powertrain, the brief for the T.50’s gearbox was similarly comprehensive. It had to be extremely lightweight while remaining a robust semi-structural component; it should have an outstanding gearshift feel; and it had to meet Murray’s exacting, compact packaging specification. Murray insisted the gearbox be both short and narrow to fit into the car’s compact dimensions and to avoid any interference with car’s pioneering ground-effect aerodynamics.
A totally-bespoke, transmission of exceptional quality – the ultimate gearshift
The six-speed manual ‘H-pattern’ short-throw gearbox that resulted from the brief is a piece of exceptional design. Being totally bespoke, it was possible to optimise every component for weight. Remarkably, the Xtrac team created a super-strong, but extremely light aluminium housing that was cast at just 2.4mm thickness.
During early testing, the gearchange motion and weighting was honed meticulously, with adjustable actuators fitted to all parts of the gear linkage. Signed-off personally by Murray, the painstaking testing process ensured that the end result was perfect in every way.
The final gearbox has a short throw and a narrow cross gate for smooth, crisp gearchanges. It features five close ratios, geared for acceleration, with a longer sixth ratio for cruising.
Engine and transmission – Technical specification
| Engine | |
| Type number | Cosworth GMA |
| Configuration | V12 semi-structural |
| V-angle | 65° |
| Capacity | 3,994 cc |
| Bore | 81.5 mm |
| Stroke | 63.8 mm |
| Compression ratio | 14:1 |
| Max power | 663 PS @ 11,500 rpm |
| Power to weight ratio | 672 PS per tonne |
| Weight to power ratio | 150 kg per 100 PS |
| Max torque | 467 Nm @ 9,000 rpm |
| Flexibility | 71% of max torque @ 2,500 rpm |
| Maximum rpm | 12,100 rpm |
| Valve train | Gear driven double overhead camshafts |
| Inclined axis 4 valves per cylinder – variable valve timing on inlet / exhaust | |
| Induction system | RAM induction airbox – 4 throttle bodies – Direct Path Induction Sound |
| Exhaust system | Inconel and Titanium |
| Lubrication system | Dry sump |
| Cooling system | Water-cooled – twin aluminium front radiators |
| Oil cooling system | Single aluminium rear radiator |
| Ignition system | 12 individual coils 12-volt |
| Starter/alternator | 48-volt gear driven integrated starter / generator |
| Exhaust emission control | 4 catalytic convertors with Lambda sensors and secondary air injection |
| Engine block | Aluminium alloy |
| Cylinder heads | Aluminium alloy |
| Connection rods | Titanium |
| Valves | Titanium |
| Total engine weight | 178 kg |
| Engine mounting | Semi-structural-inclined axis shear mounting (IASM) |
| Power density | 166 PS-per-litre |
| Transmission | |
| Configuration | Transverse with high-speed bevel gears and spur gear final drive |
| Speeds | 6 speeds + reverse: full synchro mesh |
| Gear change | Manual H pattern with reverse lock-out |
| Differential | Limited sup (Salisbury) |
| Clutch | 184 mm diameter – Triple plate carbon silicone and titanium |
| Drive line | Tripod joints and gun drilled drive shafts |
| Casing | Aluminium alloy |
| Lubrication | Pumped lubrication |
| Oil cooling | Single aluminium alloy radiator |
| Ratios | |
| First | 2.833:1 |
| Second | 2.095:1 |
| Third | 1.577:1 |
| Fourth | 1.226:1 |
| Fifth | 0.971:1 |
| Sixth | 0.744:1 |
| Input bevel | 1.688:1 |
| Final drive | 3.176:1 |
| Optional overdrive (6th) | 0.595:1 |
| Weight | 80.5 kg |
Source: Gordon Murray Design
Photograph: Gordon Murray Design
