Mark Houlahan
Tech Editor, Mustang Monthly
September 1, 2008
Photos By: Drew Phillips

There's no denying the fact that the S197 Mustang has been a huge sales success. From the V-6 automatic convertibles lining the rental car parking lots to modified GT coupes running down the 1,320 looking for that last bit of power, '05-'08 Mustangs are everywhere.

The popularity of this latest generation is one reason we see so many specialty Mustangs as well. We're not just talking about the Steeda, Saleen, and Roush vesions, but limited-run-even one-off-built-to-order specials from speed shops across North America.

Of course, the Ford top brass aren't likely to miss out on a potential sale, either, and as a result, the company has given us its own string of successful specialty models such as the V-6 Pony Package, the GT/CS and, most recently, the Bullitt. But nowhere has a Mustang specialty model been more enthusiastically revered than with Ford's reborn relationship with the legendary Carroll Shelby and his Las Vegas-based Shelby Automobiles Inc.

The reuniting of Shelby and Ford first came to light with the '06 Shelby GT-H Mustang, which was only available for rent through select Hertz rental-car facilities that featured the Hertz Fun Collection. The introduction of this car was no coincidence-model year '06 marked the 40th Anniversary of the original '66 Hertz GT350-H "rent-a-racer."

Slowly, the 500 '06 Shelby GT-H Mustangs found their way into private hands once their rental obligations were up. The relationship continued into 2007 with the release of the GT-H convertible (again available only for rent at Hertz), Shelby GT500 Mustang, and Shelby GT coupe. Ford built nearly 11,000 GT500s and less than 6,000 of the Shelby GT coupe.

While all of these cars have proven to be hugely popular, no matter what the window sticker says, there's no doubt the name Shelby has helped to sell them as much as the styling and performance.

One popular selling point for the Shelby GT has been that the cars are finish-assembled at Shelby Automobiles and are listed in the Shelby registry, just like a classic Shelby or Cobra.

Once again for '08, the Ford and Shelby relationship has grown with the continuation of the GT500, the Shelby GT in coupe and convertible, and now the limited-production GT500KR.

The KR is Shelby and Ford's latest creation, with development by SVT and performance enhancements courtesy of Ford Racing Performance Parts, with final assembly by Shelby Automobiles. It's no coincidence that the KR is an '08 model, allowing Ford and Shelby to tout another 40th Anniversary-this one celebrating the original '68 GT500KR, also shown to the public for the first time at the same New York Auto Show as the '08, 40 years before. Ford and Shelby have pushed the '68/'08 synergies to the max with the new GT500KR production figures of 1,570 units, matching the original '68 sales numbers, using the same stripe lettering font, and more.

We were lucky enough to be part of the KR's media launch event at Miller Motorsports Park in Tooele, Utah, home to the Ford Racing High Performance Driving School. Not only did we get ample seat time in Ford's latest Mustang, but Team Mustang, Ford Racing, and the SVT folks were all on-site to stress their "Steed for Every Need" mentality by allowing us to sample a plethora of examples from the Mustang lineup. Everything from a base V-6 to the new Bullitt and "regular" GT500 were available for evaluation.

Like A Million Bucks
No, it won't take that much money to call a GT500KR your own (we'll get to that later). We're talking about the looks of the KR itself. If there's one thing to be said about the current Mustang's styling, it's that it has a powerful presence. With the KR, the people at both SVT and Shelby Autos have taken that concept further and improved upon it.

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From the enhanced aero work on the car to the subtle touches of visible carbon fiber, the KR is distinctly in its own element. As for the scooped and vented carbon-fiber hood, it truly is the icing on an already very tantalizing cake. This masterpiece of autoclave goodness isn't just to make the KR look pretty (which it does in spades). Nor is it simply to save some weight, which it does to the tune of 11 pounds less than the stock GT500 aluminum version. What makes this hood special is that it truly is an example of functional Air Management 101.

Computational Fluid Dynamics (CFD) were utilized to optimize the cold-air induction system as well as heat extraction. The hood features two chambers, one for the fresh-air inlet by way of the forward intakes to feed the Ford Racing cold-air induction, and a second chamber to extract warm air from the engine area through 10 smaller openings exiting the rear extractors. Add a set of sweet-looking, fully functional hood pins and you've got yourself one uncompromising piece of automobile art. The Ford and Shelby brass on-hand were tight-lipped about the actual hood cost, but we're guessing it's a good chunk of the KR's premium price tag.

Of course, the new carbon-fiber hood (the first for any Ford vehicle) isn't all we're here to talk about. Elsewhere in the KR's stable of good looks, you'll find mirrors wrapped in carbon fiber, a revised front splitter-also made out of carbon fiber-and a more aero-worthy rear spoiler to aid in increased downforce. These are but some of the KR's exterior design attributes.

Further examination of the KR's flanks will net you more changes front and rear with the classic "SHELBY" lettering spaced and centered on the rear decklid and the leading edge of the hood, while brushed aluminum rings in the lower fascia are at the ready for the full race-ready "Track Accessory" brake cooling duct kit found in the trunk of each KR upon delivery. Finally, a revised faux fuel cap graphic at the rear of the car announces to those being passed by the KR that it is indeed the King of the Road-but better look quick before the KR disappears beyond the horizon!

Stop, Go, And Handle
It's not often that a production car is as balanced as the KR. We've endured years of Mustangs with decent power and lousy brakes (raise your hands Fox owners), as well as countless other Mustangs that had a good start in one direction, but didn't really have it all.

The KR's development team worked together on all facets of the car's suspension, handling, braking, and engine per-formance to ensure each design tweak complemented other areas of the car instead of fighting against it. Ford engineers worked hand-in-hand with people from Shelby Automobiles as well as the guys in the white coats (actually more like red Polo shirts) at SVT and Ford Racing.

When the dust cleared, this group of hard-core performance junkies delivered one amazing performance machine, both within the build and budget parameters of the project. The result? How about 1.0 g of lateral acceleration on the skidpad, 40 more horsepower, 30 more pound-feet of torque, 0.7 quicker in the quarter-mile, and improved braking over the GT500, just to name the obvious.

Of course, there's a lot more going on under the KR's skin, too, with a lowered ride height, stiffer springs, shorter rear gearing, cold-air intake, recalibrated engine management, and a completely upgraded aero package resulting in just 54 lb-ft of aero moment at 120 mph. That's a whopping 92 percent increase over the GT500-mainly due to the revised front splitter, which is deeper, has a consistent shape, and reaches all the way to the leading edge of the front wheel openings, similar to another legendary {{{Mustang}}} of recent times, the '00 Cobra R. The splitter plays a significant roll in the KR's total downforce improvement of 31 percent over the GT500.

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Step By Step

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Frankly, nothing was overlooked when developing the KR, from shift-throw ratio of the Tremec six-speed to a unique KR-only alignment spec. The wheels, made by Alcoa for {{{Ford}}} and Shelby, feature more radial and lateral stiffness, while the Goodyears that are wrapped around them-P255/45ZR18s in the front and P285/40ZR18s out back-were specifically designed for the KR with revised rubber compound and steel-belt construction.

The KR's ABS and traction control systems were both remapped to take full advantage of the new tire, wheel, and suspension packages. Behind those sweet forged wheels are Brembo 14-inch rotors with fixed, four-pot calipers up front, and 11.8-inch rotors with single-piston calipers at the stern.

Rounding out the performance improvements is a completely redesigned exhaust system that features a revised crossover, all stainless steel construction (where most of the KR's 22-pound diet over the GT500 came from), and smaller, more cylindrical resonators utilizing the '08 Bullitt Mustang glasspack tips. An elevated axle-vent reservoir, which prevents expulsion of gear oil during extreme performance driving, is found at the rear, coming straight from experience gained in the FR500C racing program.

Get In, Sit Down, & Hold On
So what's it like climbing into the leather-clad cabin of the KR and putting the most powerful production Mustang ever built through its paces? For starters, we had ample seat time to evaluate the KR on the surface streets and nearby highways of Salt Lake City. Upon walking up to the car, the more muscular overtones were immediately evident. We absolutely loved the hunkered-down stance and revised aero package. Admittedly, we wished the production car kept the concept's 20-inch wheel package, only because the S197 wheel openings are so big, but we got earfuls of engineer-speak about unsprung weight, braking forces, and so forth.

Once inside, the first thing that put a grin on our faces was the exhaust note that greeted us upon twisting the key. The enhanced sound quality of the exhaust was a welcome change to the usually muted OE systems found on modern Mustangs. It'll be hard to beat this setup in the aftermarket. During driving maneuvers, the exhaust was right there at the back of the car, but not overbearing, and without a hint of drone. But all it took was a tickle of the right foot to bring the exhaust tone up to announce our arrival (hey, even a guy on a sport bike gave us a thumbs up when we revved the engine at a stoplight).

Speaking of revving, the KR loved to do that all day long. From a nice, smoky burnout to high-rpm freeway passes, we found ourselves quickly climbing the tach. The clutch effort in the KR was very much like the GT500's, with the same twin-disc clutch setup between the 5.4 modular and the Tremec six-speed. This allowed us to even enjoy (if you can call it that) some stop-and-go traffic without praying for an automatic-heaven forbid-or the nearest off ramp to take a leg break.

The KR's shifter, topped with a classic white ball, is from the Ford Racing parts bin and features a 25 percent shorter throw than the GT500's. Frankly, this baby needs to be the stock shifter in every new Mustang as far as we're concerned. If you've ever missed a gear due to the rubber-hose-in-a-box-of-rocks-feel shifter, you owe it to yourself to upgrade the handle in your S197 to this unit. It'll make even your daily drive to the office more fun-we guarantee that.

The suspension on the KR, while more firm than the GT500, didn't beat us up, even when spending serious time in the driver seat. When we first saw the lowered stance we thought we'd be needing kidney belts, but instead were pleasantly surprised that the engineers did a top-notch job of recalibrating the shocks and struts, sway bar diameters, bushing durometers and, of course, the spring rates themselves. It's a very compliant ride that will work on the freeway or your favorite corner at Miller Motorsports Park (which we soon realized with track time the following day).

One of the Shelby's trump cards, in our opinion, was the braking. With those huge Brembo rotors up front and four pistons clamping down on the rotors, the KR's 3,879 pounds slow to sub-warp speeds better than the GT500 by a bit over half a car length. The KR is 22 pounds lighter than its GT500 sibling, but due to the suspension tuning, gear ratio, and aero package, the KR has a considerably lighter feel, which takes steering inputs at will and makes you believe you're driving a much lighter car.

It's Miller Time
Day two of our press function allowed us a full day's use of the Miller Motorsports Park's West Course for vehicle evaluation. The Miller facility is one of the best in the world and, due to its immense size and location, the track has considerable runoff areas with little to no barriers, allowing drivers to go full steam with little chance of damage should they get in over their heads.

{{{Ford}}} had several GT500KRs for us to test. They were showroom stock-with no prep for track use-so we could see just how much at home the KR is on the track as it is on the street. Besides a quartet of KRs, Ford's press fleet brought out production models of the GT500 and Bullitt Mustangs to compare back-to-back with the KR, while Shelby Automobiles allowed us to taste the CS8 for comparison sake. Needless to say, it was a day of driver changes and organized Chinese fire drills as helmeted journalists leapt from car to car.

To get an accurate feel for the KR's improvements, we worked our way up the ladder proper by starting in a Bullitt Edition Mustang, then to the GT500, and finally the CS8 before tasting the KR's track manners first hand. While some of our driving time was strictly to learn the Miller West Course layout (our first time there), we did get to run several laps in each car at the limit; or more succinctly, at our limit. Wreck one of these bad boys and it's not just $20 a week out of your pay, that's for sure.

Right off the bat, we felt that the KR's suspension was ready to handle every inch of the track. We could brake harder, corner later, and accelerate deeper with the suspension's undying ability to instantly go where the car was pointed. No excessive body roll, no deep nose dives on hard braking, nothing dramatic at all-just a balanced car allowing us to put our best inputs into making great lap times.

While we didn't get to run the full Miller course, we're sure the KR's new aero package still played into our slower speeds on the West Course. Braking was spot-on and fade-free, while the power on tap was more than enough for ear-to-ear-grin-inducing full-throttle romps on the straights. We noticed the KR's recalibrated electronic throttle control allowed instant throttle as we rolled into the power coming out of the turns-no delays or hesitation on the computer's part whatsoever.

After several laps in the KR at speed, or what we thought was a decent speed, we had a chance to climb into one of the KR development cars for a few laps with SVT engineer Andy Vrenko. Now the term "development car" is a bit of a misnomer here, as, save for the racing seats and five-point harnesses, the development mules were identical to the street-going KRs down to the tires, brake pads, upgrades, and so forth. This allowed the SVT engineers to fully test the production car's hardware and calibration/tuning in a demanding 12-hour non-stop track test.

Andy's driving skills were immediately noticed as we powered through the first turn in near full drift with the tires howling their displeasure. Two laps later, the E-ticket ride was over but we wanted more. Andy clearly knew the limits of the KR's suspension and brakes (as he should since he developed them) and put the KR assuredly wherever he wanted it to go. This is one easy-to-drive, yet capable, car that won't beat the snot out of your backside.

Step By Step

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Your wallet, on the other hand, is another story. Suggested retail on the KR is currently $79,995. Don't be surprised by dealer gouging, er, we mean "adjusted dealer markup," which enables the KR to hit $100,000 to get it off the showroom floor.

So not only is the KR the most powerful Mustang ever built, it also will hold the distinction as the most expensive Mustang ever built. Unfortunately, this means that the KR will be out of reach of many of the enthusiasts who truly would enjoy the car and use it properly, myself included. But hey, a test drive is free, right?

Carbon-Fiber Hood Properties

  • Fully functional hood pins
  • Used Computational Fluid Dynamics (CFD) to optimize heat extraction and cold airflow to intake
  • 1.2mm unidirectional outer panel
  • 0.8mm unidirectional inner panel
  • Chamber 1 - fresh-air feed to cold-air intake
  • Chamber 2 - warm-air extraction from underhood
  • Inner hood designed to manage water from the extractors
  • 11-pound weight save versus alum. GT500
  • Suspension Upgrades
    Springs and Stabilizer Bars

  • Lowered front-ride height, 20 mm versus GT500
  • Lowered rear-ride height, 15 mm versus GT500
  • Front-wheel rates increased 17 percent, rear-wheel rates increased 7 percent to balance front-, rear-ride frequency
  • Stiffer springs control pitch, squat, and roll stiffness
  • Less total understeer than the GT500 with same overall roll stiffness as the GT500
  • Unique alignment--more negative camber (-1.4 deg. versus -0.75) and 0 front toe
  • Performance Upgrades

  • 3.73 axle ratio increases "slope" of acceleration
  • Increased spark advance improves throttle response and increases torque and power
  • Modified electronic throttle curve to increase performance feel
  • Cold-air intake reduces intake pressure drop and the temperature of air going into the airbox
  • Performance Numbers (unofficial SVT)
    0-60, sec4.54.3
    60 feet, sec2.22.0
    1/4-mile e.t.12.812.1
    1/4-mile, mph112115
    Top Speed, Electronically Limited155

    100-0, feet310303
    60-0, feet115109
    {{{300}}} ft skidpad, g0.921.00
    Slalom (100 ft), mph68.571.7
    Horsepower, hp500540
    Torque, lb-ft480510
    Rise Over Ambient (F)37<32

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