Martens: IRS ‘Not Necessary’ for High-Powered Shelby Cobra

DEARBORN – When Ford Motor Co.’s Special Vehicle Team (SVT) returns to the U.S. performance scene in the summer of 2006 with the Mustang-based Shelby Cobra GT500, something will be missing.

Yes, it will come with output rated well in excess of 450 hp, and its price tag will toe the $40,000 line, but crawl under the rear overhang and you won’t find an independent rear suspension, even though it originally was on the agenda.

“It’s not necessary, “Phil Martens, group vice president-product creation, says at a vehicle preview here.

“You can always say you’ll get some attribute benefits (from IRS), but when you get the geometry right, you really don’t (need) it,” Martens says. “It’s hard to understand, and the purists will disagree with me. But when you drive the vehicle, it speaks for itself.”

Shelby Cobra GT500 will debut next summer.

Ford shows the Shelby Cobra GT500 at the New York International Auto Show, alongside SVT’s Sport Trac Adrenalin SUV and a new game plan for the in-house performance unit. (See related story: Sport Trac Gets SVT Treatment in 2007)

In January 2004, Martens told Ward’s the next-generation Cobra would carry IRS, but that thinking has changed: “What finally did it were two things,” he says of the decision to dump IRS for a solid rear axle.

“One was, frankly, the suspension geometry wasn’t as good as the geometry on the solid rear axle – and I mean damper ratios, spring ratios, overall geometrical performance,” he says. “The second thing was we didn’t want to have all that weight in the vehicle. It added about 180 lbs. (82 kg).”

Ford long has contended its solid rear setup has few penalties, if any, when stacked up against an IRS, thanks to a number of rear-suspension engineering upgrades introduced for the ’05 Mustang, that was developed under the eye of Hau Thai-Tang, SVT director. (See related story: Mustang Sally Gets Her Groove Back)

“When you don’t have the right suspension geometry and you add the weight, you actually are then asking yourself, should we do that?” Martens says. “Then the question is, can you get the right tire size in? We can get the right tire size in. And with all of that, the way this rear suspension has performed really has exceeded our expectations.”

In fact, the SVT team pretty much left the base Mustang’s suspension intact, choosing to re-tune or upgrade components where needed, including changes to shocks, spring rates and stabilizer bars. The 19-in. wheels are coupled with 14-in. (36-cm) Brembo rotors in the front and 13-in. (33-cm) discs in the rear.

The auto maker says the new Mustang has cleaned house on the Grand-Am Cup racing circuit since its debut, beating a host of vehicles that ride on an IRS.

Although Martens does not mention it, another factor likely was cost. An IRS, while capable of improving handling in many cases, is more expensive than a solid setup. Ford aims to continue to offer Mustangs – no matter how revved up – at an affordable price.

“We haven’t talked (publicly) about price yet,” he says, but it will come in “somewhere around $40,000.”

While Ford may be accused of overselling its solid rear axle, it probably is underselling the Shelby Cobra’s engine output.

The vehicle carries a supercharged 5.4L V-8, first seen in the low-volume, 385-hp ’00 SVT Mustang Cobra R and revised with some engine components from the GT supercar program.

Ford initially reports the vehicle is capable of “at least” 450 hp and 450 lb.-ft. (610 Nm) of torque, but Martens says those numbers will be upped, with an announcement likely at next year’s Detroit auto show.

“We haven’t defined what the upper limit is yet,” he says, promising the most-powerful factory-built Mustang ever.

Ford sources say the vehicle will be more capable than the figures ultimately published. The auto maker was burned in 1999 by touting a 320-hp figure not attainable by Cobra buyers and then having to issue a recall to fix the situation. When an updated SVT pony car bowed in 2002, Ford erred on the side of caution, saying it was capable of 390 hp, even though it easily broke the 400-hp threshold. (See related story: Ford: SVT Cobra’s 390 hp for Real)

The 5.4L 4-valve mill is mated to Ford’s T-56 6-speed manual gearbox, which is currently utilized in the Mustang FR500C racecar. The engine’s aluminum cylinder heads, piston rings and bearings come from the GT and a “Powered by SVT” camshaft cover serves as the under-hood signature.

The exterior of the car, featuring bold vertical racing stripes, an air splitter cut into the hood, revised headlamps and a cobra badge on the grille, harkens back to the ’68 Shelby Cobra that helped solidify longtime Ford affiliate Caroll Shelby as a top-tier Mustang engineer. Shelby had a hand in the building of the current car, the auto maker says, and his name is featured prominently on the rear decklid.

Inside, Shelby Cobra badges, snake logos and leather dress various surfaces. Titanium and aluminum also figure prominently in the cabin, Ford says.

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