Tom Wilson
November 3, 2010
Contributers: KJ Jones Photos By: Henry Z. De Kuyper, KJ Jones

Last year we fielded a 14-year-old daily driver Mustang Cobra in the inaugural Castrol Syntec Challenge. It was a game move, putting up a lightly modified '94 Cobra against a bunch of mega-dollar cars representing other magazines, and we did well to finish fourth. However, like the editors of the other five magazines involved (Super Street, Import Tuner, Eurotuner, Honda Tuning and Modified Magazine), Big Steve wanted to step up our game this year. And so Carlos Cortez's '07 Mustang Shelby GT500 convertible got the nod.

Carlos' car's main attraction is nuclear thrust. The GT500s are no slouch off the showroom floor, of course. With Carlos' ride wearing the first Vortech VTS supercharger upgrade, it packs a Herculean hit that's guaranteed to make almost any competitor run and hide from contests of brute force.

Of course, the Castrol Syntec Top Car Challenge is far more than a drag race. The contest includes a dyno evaluation, emissions test, 180-mile endurance drive, 0-to-60 acceleration, 80-to-0 braking, power-to-weight calculations, and a fastest-lap shootout on the road course. Therefore our GT500 was further prepped to enhance its all-around game (see "Maxed Out" on page 64 in our Oct. '10 issue and "Topped Off" elsewhere in this issue).

Because the Castrol Syntec Top Car Challenge is far more than a drag race, testing the participants is a three-day affair, opening with a dyno test at K&N Performance in Riverside, California. A best-of-three power pulls are made on K&N's Superflow chassis dyno, followed immediately by an emissions test.

Once everyone has their chance on the dyno's rollers, the Top Car entourage hits the road and rumbles through street and highway traffic, on the three-hour grind up to Buttonwillow Raceway Park in California's sweltering central valley. At Buttonwillow, Day 2 is dedicated to testing in the standing quarter-mile, 0-60 acceleration, and 80-0 braking. Day 3 is spent lapping Buttonwillow's "big track" in search of the single-fastest lap.

Points are awarded mainly, but not completely, as a percentage of the best competitor's performance, which makes it impossible for competitors to keep tabs on how everyone is doing. Furthermore, while some results are plainly evident to anyone watching, others, such as the officially clocked lap times, are known only to the officials, and they keep those a secret for a couple of months so the news doesn't leak out early and spoil the fun.

We certainly had the power this year, and as long as the brakes stayed close to their operating temperature, our Shelby GT500 had fabulous braking, along with good emissions and unimpeachable street-car credentials. If we have to call something an Achilles' heel for our combination, it's definitely the car's excessive weight and limp chassis.

I'll finish by saying I love road racing, but that particular discipline of motorsports asks a lot of a street car. It's impossible to brake or corner anywhere as hard and as repeatedly on the street as is the norm on the track. The qualities that make a great track car also contribute a lot to having a punishing street car. But the perceived catch-22 is that great street cars usually tend to fall apart on the track. Our Top Car challenger dispelled that theory.

In the final analysis, I'm jealous of Carlos' ability to take his GT500 (and its sledgehammer performance) for a long, spirited cruise through the canyons of SoCal, tunes playing, fresh air blowing, and massive power burst always at the ready. His ride is a fabulous street car with wonderful driveability. And by bettering its competition in outright power, and finishing a close second in the acceleration and braking tests (and being just a touch below emissions standards with long-tube headers), this GT500 definitely is a winner with us in its intended street environment.

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On the Dyno
Dyno day was Wednesday on the Superflow chassis dyno at K&N Performance. Top Car Challenge rules allow each entry to make three pulls with five minutes to cool down between runs.

For Carlos Cortez's Shelby GT500, Technical Editor KJ Jones elected to make two runs back-to-back, then ice down the 5.4's Lysholm twin-screw supercharger and intake tract for 10 minutes, figuring the two quick runs would warm and thin the oil, then the longer cool-down would allow cooler inlet air temps.

This proved to be a great plan, as Carlo's beast ripped off two perfectly repeated 650hp passes, and followed up after the ice treatment by cranking out an additional 15 hp to post 665 ponies at the feet. Only the turbocharged Toyota Supra could come somewhat close to that figure, whining out a respectable but distinctly second-place 590 horses.

A brief cool-down immediately followed each car's power passes on the dyno, followed by a 2,500-rpm emission test. Lasting 90 seconds, the sniffer didn't encounter anything it didn't overwhelmingly like about our Shelby, despite its long-tube headers, lack of catalytic converters, and potent fuel.

On the Road
The cruise portion of the Castrol Syntec Top Car Challenge was a non-entity for Carlos' Shelby GT500. A low-mileage bolt-on car, the GT500 ran the six different freeways, surface streets, and grinding stop-and-go traffic in 100-plus-degree heat with the AC cold as ice. An on-board data logger showed the water temperature seemingly glued to 185 degrees, and mileage measured 18 mpg for the 180-mile, approximately three-hour grind.

And we should emphasize Carlos' Shelby is absolutely a street car (one heck of a street car, we might add). No rattle-trap shaker, the GT500 is a 3,700-mile cruiser devoid of squeaks or rattles. The stereo blast tunes; the stock AC is, if anything, an over-achiever; the stock seats are cushy leather; and above all, it can drop its top for open-air enjoyment.

Stop and Go
At Buttonwillow Raceway Park, the first point of business was evaluating the dragstrip performance for each 'Challenge entry. The facility uses a portable dragstrip setup (complete with staging beams, a Christmas Tree, and 60-foot and quarter-mile time and speed), which was set up on the long back straight of the relatively flat and slightly technical road-racing circuit.

Our Maximum Motorsports crew disconnected the GT500's front sway bar for better weight transfer, the tire pressures were let down in back to 18 psi, and Tech Editor Jones slid behind the wheel. Three runs were allowed, with KJ opening via a wheel-spinning 12.07-second rodeo ride. As KJ put it: "It was a little on the edge, sideways, with just a haze of the tires in Third gear."

Knowing a little softer was the answer, KJ toned down the launch and shifts, but backed up to a 12.24. As anyone with experience in high-powered, high-torque cars with stock-type suspensions can attest, a beast like this is not easy to drive. Luckily, KJ has the skills, and on the final pass managed to find what he calls "the perfect storm," which resulted in a beautiful run to 11.76 at 124 mph.

"Carlos' car pulls like a freight train," says KJ. "Without being allowed to do any type of burnout, making a good, clean dragstrip pass isn't easy in this Shelby-especially with street tires on a surface that has not been prepped in any way. I had to process everything really quickly on each pass, because before I knew it, the car had pulled right to that point where the tires were starting to spin."

Along the way, onboard timing equipment gave the 0-to-60 time at 3.9 seconds. Together, the quarter-mile and 0-to-60 runs highlighted the Shelby's muscular strength. Only the Nissan GT-R could best it, thanks to the Japanese car's combination of good power, lighter weight, and far superior all-wheel-drive traction and electronic launch control.

All brake testing was done by a designated test driver and run from 80-to-0 mph. Everyone was surprised just how well the GT500 did, perhaps because they recall last year's '94 Cobra with its unbedded brake pads and excruciatingly long stop from the same speed.

The GT500's giant Brembo brakes and Hawk HPS Plus street pads anchored the big convertible in an eyeball-popping 173 feet! That's a lot better than in 2009, and a dramatic illustration of the importance of pad bedding.

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On the Track
Lap times were set on the third and final day of the 2010 Castrol Syntec Top Car Challenge, with an hour of open practice before a 15-minute, officially timed session. The single-fastest lap is tallied, with double points awarded to the winner because traversing a road course (in the least amount of time) encompasses all aspects of a car's performance; testing a vehicles balance and finesse through transitions the more specialized tests miss.

Before hitting the track, the Maximum Motorsports crew swapped the Hawk HPS Plus street brake pads for gnarly Hawk DTC-60 race pads front and rear. After the pad change, I took the car out on the deserted roads around the racetrack to bed the pads, which gave me an introduction to the Shelby's hairy power.

On the road the car was a joy; an easy-riding, power-crazed unit with noticeably more tone in the handling than that of factory-suspended GT500s. The only squawk was a flat spot in the throttle right off idle, but it was a momentary thing, and with 124 mph in the quarter, it wasn't hurting power delivery any.

Still, just one little squirt of the throttle and we knew we were in for a tough hour and 15 minutes on the track. And we were. Carlos' car has the power of a Trans Am racer but without the precision of a full tube-frame chassis, stiff suspension, and dedicated racing slicks. Furthermore, at 4,300 pounds in on-track trim (car with driver), Carlos' car is bending under the three-quarter tons more weight than the purebred racer.

In an effort to provide some stability to this difficult situation, Maximum had tuned out much of Ford's built-in understeer with geometry and alignment settings, but left plenty of push in via sway-bar tuning. The result was an inherently honest car (it never tried to turn around and bite us) but with so much understeer in the fast sweepers that only minimal power could be used.

On top of that, the dead spot in throttle response just above idle was right where we needed a whiff of power to pick up the front end in mid-corner. That meant either we understeered wide, started to power oversteer (so much torque down low), or simply had to crawl through the turns using almost no throttle at all. None of those are a way to set a fast time.

As you might imagine, this made for a two-fisted, lurching bronco that was difficult to keep in that narrow range where the car was balanced and the tires were giving all their grip. It was our version of the tightrope that KJ walked during his time behind the wheel in the drag test.

Just to make sure we earned our pay, the brakes, which provided excellent stopping power and modulation, faded to the floor in a couple of laps, and the usual lap or so of cool down had almost no effect. Only bringing the car into the pits and bleeding the brakes would restore raceable braking-for another couple of laps.

Some fiddling with shock settings-and most importantly-swapping in a smaller front sway bar, allowed us to put something of a flowing lap together by the end of our timed runs. Unfortunately our 2:05 best was light years behind everyone else, who hovered in the 1:57 to 1:58 range. However, on the plus side, Carlos' car was 7-seconds-a-lap faster than last year's ride.

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