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Ford Shelby Cobra Concept - Modern Day Cobra
A 605-Horsepower Testbed For What Might Be
We heard rumors that Carroll Shelby and Ford might be up to something. But we misinformed our readers when we stated in our Jan. '04 issue that Shelby was involved in the Ford GT project. Well, we were right and wrong-well, more wrong than right on that. But, Shelby is involved with Ford on their new Shelby Cobra Concept car. And what a cool car it is. We have to wonder on this one-if it does come to pass, is it Ford's answer to the Viper? Maybe what we are looking at is a mid-60 grand car that will compete with the Chrysler V-10 powered snake. It sure seems like a carbon copy of what Shelby is famous for-sleek styling, minimalist interiors, and big power out front. Whatever the case, we like the idea and hope to see more on this from the Ford corporate offices.
In an atmosphere that is part think tank and part speed shop, the Advanced Powertrain team develops technologies that frequently have as many applications on the racetrack as in consumer vehicles.
For approximately two years, they had been working on an all-aluminum V-10 targeted at ultimate, naturally-aspirated performance. When they bolted this beast into a Mustang chassis for evaluation, it only took one drive to confirm its potential.
"The Ford Shelby Cobra concept just begged for this engine," said Graham Hoare, director of Ford Research and Advanced Engineering. He continued, "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 famous 427."
Blending the Advanced Powertrain team's work with elements from the 4.6 liter, 4-valve V-8 used in the '04 Mustang Mach 1, the resultant Ford Shelby Cobra concept engine has 10 cylinders and is bored and stroked for a 6.4-liter displacement, or about 390 ci. It produces 605 hp at 6,750 rpm and 501 lb-ft of torque at 5,500 rpm without supercharging or turbocharging.
"In many ways, it's not very exotic," said Hoare. "It uses the same basic castings and assembly techniques as our production modular-engine family. The output, though, is phenomenal. If you can't get in trouble with this kind of power, you're not trying hard enough."
Kevin Byrd, the V-10 project leader, thinks of the Cobra V-10 as an all-star combination of current Ford engine technologies. "This engine is an amalgam of everything right about Ford engines. We took the best the modular-engine family has to offer, then added some tricks of our own. The V-10 is a culmination of 100 years of building engines," he said.
The double-overhead-cam cylinder heads and cylinders are fed by port fuel injection and racing-derived velocity stacks that are just visible within the hoodscoop. For a low hood line, the throttles are a slide-plate design, and the lubrication system is the dry-sump type, which relocates oil from underneath the engine to a remote tank. The engine proudly wears brushed aluminum "Powered By Ford" valve covers.
The rear-mounted, six-speed transaxle is identical to the high-performance unit in 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 drive ratios, this Ford Shelby Cobra concept has a theoretical top speed of more than 260 mph and would break 130 mph in third gear, although it's electronically limited to 100 mph-for now.
Front-Mounted Engine And Torque Tube
One of the challenges of fitting a 10-cylinder engine into a compact roadster is leaving enough room for the driver's legs and feet. With a conventional transmission mated to the back of the engine, the tradeoff between hood length and passenger room often makes for a cramped footwell and offset pedals-a flaw of the original Cobras and many modern sports cars.
Because the Ford Shelby Cobra concept was planned from the outset to be a production-feasible "runner," not just a pretty show car, the team had to address the legroom concern. They found mounting the transmission at the rear of the car, connected to the front-mounted engine with a torque tube, let them use a very narrow "tunnel" between the seats.
Creating a New Chassis From Existing Parts "We knew we wanted a front-engine car that had to be ultra-compact and lightweight, yet robust enough to handle 605 hp," said Theodore Rumple, who worked on the chassis design. "There was nothing that fit the bill on first glance."
But Rumpel's team saw a creative solution. "We were already planning to use the Ford GT suspension systems, and we asked ourselves how much more of the GT we could borrow," he said.
Quite a lot, as it turns out. Even though the GT is a mid-rear-engine car, and the proposed roadster was to have a front engine, a decision to mount the transmission at the rear made the connection.
"Once we really started looking into it, we had an epiphany," Theodore said. "The project took on a new sense of purpose when we really started leveraging the Ford GT engineering."
The team worked long hours with John Coletti, head of Ford's special vehicle Team, to maximize the commonality. Fresh from completing the all-new Ford GT in just 15 months, Coletti understood what it took to build fast cars faster. "It was a great team effort," Coletti said.
The bulk of the rear structure is made from slightly-modified Ford GT components, including the massive, trellis-like cast aluminum suspension nodes, the rear rails and bumper beam, a major cross-member, and the brackets used to mount the transmission.
Ford GT Suspension, Steering, And Brakes To attach the massive 18- and 19-inch wheels and tires to the car, the team chose to use the Ford GT suspension system, with a few modifications to accommodate the increased weight up front. Like engine technology and electronics, suspension design has come a long way in the past 40-plus years.
The new Ford GT earns praise for its combination of agility, grip, and easy-to-drive character-a reflection of its sophisticated suspension design and the expertise of its chassis engineers. The Ford Shelby Cobra concept applies the best of the GT suspension to a big-engine roadster.
A double-wishbone suspension design, with unequal-length aluminum control arms, coil-over monotube shocks, and stabilizer 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, yet retains the strength of forging. The metal, heated to just below its melting point, is the consistency of butter when it is injected into a mold 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 column, like the Ford GT's, draws on Ford engineering's best practices, like the low friction, high stiffness, and light weight that have made the Ford Focus steering column among the best in the industry. Braces between the front shock towers and below the isolated engine mounts improve torsional rigidity and aid steering response.
With more than 600 hp available at the throttle, the brake pedal had to be equally potent. The team set braking distance targets comparable with today's best sports cars, and turned to the Ford GT braking system for suitable components.
Brembo "monoblock" one-piece aluminum brake calipers, with four pistons each, grab cross-drilled, vented discs at all four wheels. The discs are a massive 14 inches in front and 13.2 inches in the rear for fade-free stopping power. But the team stopped short of fitting the car with an antilock braking system, in keeping with its racing character. 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 one-piece BBS wheels are wrapped by BFGoodrich Z-rated racing slicks, size 275/40R18 in front and 345/35R19 in the rear.