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Powertrain

The heart of any supercar is its engine, and the Ford Shelby GR-1 concept's powerplant is adapted from Ford's MOD engine family. It delivers the rush of raw power from 605bhp and 501 lb-ft of torque that's associated with big 1960s V8 engines, all without the aid of forced induction.

This combination of brute force and thorough engineering has created what Ford calls "a rarity in the world of auto shows – a concept car that can actually do, rather than merely promise, 0-60 in under four seconds, and would easily exceed 200 mph if not electronically limited."

"After I drove last year's Cobra concept, I knew we had a winner in the 6.4-litre V10," said Carroll Shelby, racing driver and consultant on the Ford Shelby GR-1 concept. "We decided to transplant that engine directly into the GR-1 with practically no changes, right down to the rear-mounted transmission, which really helps the weight distribution."

For about three years, the Ford powertrain team has been working on the all-aluminium V10 targeted at ultimate, naturally aspirated performance. When they bolted this modern-day big-block into a Mustang chassis for evaluation, it only took one drive to confirm its potential.

"When we found out there was yet another concept car with the Shelby name on it, we knew it begged for this engine," said engineering director Graham Hoare. "Although it's not yet ready for production, we've reached a credible engineering level for such a serious concept car – and it has a modern soul that matches the Shelby mission."

Transmission

While the Ford Shelby GR-1 concept shares a significant amount of technology with the Ford GT and the Shelby Cobra concept, the team met several unique engineering challenges head-on.

First, the six-speed manual transmission had to be packaged in a way that would not compromise the occupant footwells. "One of the unique solutions we delivered for the GR-1 concept was the design, engineering and development of a torque-tube driveline, which allows placement of the transmission in the rear of the car behind the occupant zones," said advanced product creation manager Manfred Rumpel.

It shares its rear (live) axle assembly with the Ford GT, with an integral limited-slip differential to drive the rear wheels. Based on the engine's 7,500-rpm redline and the wide drive ratios, this Ford Shelby GR-1 concept has a theoretical top speed of around 200 mph, although it's electronically limited – for now.

The transaxle application was mandated by the desire to fit a large engine into a compact coupe while leaving enough room for the driver's legs and feet. According to Ford, with a conventional transmission mated to the back of the engine, the trade-off between hood length and passenger room often makes for a cramped footwell and dramatically offset pedals.

Mounting the transmission in the rear helped to more evenly distribute the vehicle's weight and increased the footwell area from 16.5 inches to 21.7 inches, resulting in almost three inches more legroom than in similar performance vehicles.

The legroom-saving torque-tube driveshaft runs at engine speed, considerably faster than typical driveshafts mounted to rear of the transmission. The spinning inner shaft is supported within a stationary outer tube that stabilises the engine and transmission in bending and in torsion. The inner shaft taps crankshaft torque via a twin-disc, small-diameter clutch mounted at the rear of the engine.

Computer-aided design was essential in helping the first prototype come together smoothly.

"Because they spin so much faster than driveshafts, these torque tubes can be a challenge to execute properly in terms of vibration," said Rumpel. "Using our electronic tools, we optimised the location of the driveshaft support bearings, and it ran smoothly on the very first try. This type of modern engineering tool gives us a development advantage that pioneers like Carroll Shelby could only dream about."

Suspension

A double-wishbone suspension design with unequal-length aluminium control arms, coil-over monotube shocks and anti-roll bars is used front and rear. The upper control arms are identical at all four wheels and are made with an advanced rheo-cast process that allows the complexity of form associated with casting while retaining the strength of forging. The metal, heated to just below its melting point, is the consistency of butter when injected into a mould at high pressure. Pressure is maintained as the part cures, preventing porosity in the final product for exceptional strength.

The steering rack is also borrowed from the Ford GT, with a few modifications. The steering, like the GT's, draws on the Focus' steering column, featuring light efforts, low friction and high stiffness. Braces between the front shock towers and below the isolated engine mounts improve torsional rigidity and aid steering response.

Brakes

The team set braking distance targets comparable with today's best supercars and turned to the Ford GT braking system for suitable components. Brembo monobloc aluminium brake calipers with four pistons each grab cross-drilled, vented discs at all four wheels. The discs are a massive 14 inches (355mm) in front and 13.2 inches (335mm) at the rear. Brake balance is biased slightly to the front wheels to aid stability.

For packaging reasons, the team devised a novel offset actuation linkage for the brake booster and master cylinder, so the brake pedal can be placed in a normal position even though its hardware is off to the side of the engine bay. The kinematic linkage concept for the remote booster actuation was an idea borrowed from the European Ford Mondeo.

"The unique remote booster had to be just right so you can slow the car in a linear and proportional way," said Rumpel. "This means the pedal effort and travel are proportional to the vehicle deceleration rate, which is especially important in high-performance sports cars."

The one-piece, 12-spoke BBS wheels are wrapped by Goodyear Z-rated racing slicks, size 275/40R-19 in front and 345/35R-19 in the rear.

A "reality-based" concept

Much like the original Ford GT and last year's Shelby Cobra concept vehicles, the Shelby GR-1 is intended to be a fully engineered, production-feasible road-going, drivable project vehicle.

"With the Ford GT and Ford Shelby Cobra concept, we have a tremendous amount of experience quickly building high-performance cars, like the Shelby GR-1, with world-class performance," said product creation boss Phil Martens. "Our goal this time around was not to create the ultimate top-speed, high-performance sports car. Really, we intended to strike a better balance of design, capability and usability that might appeal to someone considering a Ferrari 575M Maranello."

The Shelby GR-1 starts with a modified version of the aluminium chassis from the rear-engine Ford GT. The bulk of the rear structure is made from slightly modified Ford GT components, including the massive trellis-like, cast-aluminium suspension nodes, the rear rails and bumper beam, a major cross-member and the brackets used to mount the transmission.

The centre portion of the spaceframe also borrows liberally from the Ford GT as major aluminium extrusions are based heavily on existing pieces. At the front of the coupe, the team incorporated extruded main rails, a steering rack cross-member, crash-management sections and the bumper beam from the Ford GT.

"Building a concept car with this level of sophistication is much easier when you start with a world-class supercar like the Ford GT," said Martens. "This commonality and re-use goes hand-in-hand with our speed and cost efficiency, promising the Ford GT's bang-for-the-buck equation if the Shelby GR-1 goes to production."

Overall, the Ford Shelby GR-1 concept is more than two feet shorter than the Ford GT, with a wheelbase nearly seven inches shorter. The track width has been reduced by more than an inch. Ford reckons that the concept car and the GT share any parts at all is a testimony to the flexibility of the space frame design and the creativity of the chassis team.
 
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