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Ford Shelby GT500 Track Testing - Shelby Bolt On Bonanza
How quick can a GT500 run with basic bolt-ons?
It was Grabber Orange with Shelby lettering and GT500 emblems emblazoned on the decklid and fenders, and though it was sitting still under the tower of Old Bridge Township Raceway Park, it was a four-wheeled monster looking to eat something for breakfast.
With an iron-block version of the Ford GT engine, the '07 Shelby GT500 needs no intro-duction as it makes itself known long before the key is turned and the blown 5.4-liter powerplant roars to life. Packing 500 hp, the beast is capable of low-12-second quarter-mile times with a terminal velocity upwards of 117 mph. Not too shabby for a base price around $42,000.
We all know the GT500 is fast right out of the box. Ford did a marvelous job in engineering a car that-despite its 2-ton weight-will hang with Chevy's Corvette and with the right driver can almost hang with Chrysler's big dog at the dragstrip. The thing is, why settle for an even matchup with a 'Vette or Viper when you can throw a few bolt-ons at the Shelby and thoroughly whoop some Brand-X butt?
That's why we spent a day at the famed New Jersey dragstrip flogging this issue's cover car in search of true happiness and bolt-on madness. All of the parts and pieces we tested are things anyone can do in their spare time or at the track. In Part 2 we plan to take the car further-namely into the 10s. Now, follow along as we partake in the journey of our trackside bolt-on bonanza.
As with any test, a baseline must first be established; this way, any improvement or decline in performance can be noted. First was the weigh-in: The Shelby tipped the scales at a hefty 4,080 pounds with driver, and that's a lot of mass to move from a dead stop to the 1,320 mark. Even though we were there to see what bolt-ons could do to the car, the gears in our heads were spinning trying to figure out ways to lighten the sled. But our plan was to keep all the sweet amenities of the Shelby, so little, if any, weight would be yanked. Imagine how quick the Shelby could be if you knocked 600 pounds off of its flanks?
Either way, our goal was to see how quick we could get the S197 to run both stock and modi-fied. Our test car belongs to Eddie Alterman from Bonner Springs, Kansas. With around 800 miles on the odometer, the bone-stock GT500 had sufficient break-in time, but based on past tests, we know they run better with a few thousand miles on them-oh well. To aid us in our bolt-on endeavor, we enlisted the help of Jim D'Amore and Shaun Lacko of JDM Engineering. On our list of modifications was installing a set of drag radials, reflashing the computer with a new tune, and bolting in a new after-cat exhaust system. In Part 2, we hope to return with new gears, more boost, and a cold-air inlet.
We decided to run in the right lane throughout the day, and traction was excellent. The air was on the hot side compared to what is the norm for New Jersey weather in early October, and the Shelby ran high-test gasoline the entire day. With the basics covered, tire pressure checked, and the engine up to optimal operating temperature (just above the cold line), it was time to let 'er rip and see what kind of numbers the stock Shelby could produce.
MM&FF Editor and resident car jockey Evan Smith handled the driving duties. After heating up the tires, he rolled into the beams and carefully slipped out the clutch from 4,000 rpm. The Shelby ripped off a 2.010-second 60-foot time, and finished the quarter-mile in 12.38 seconds at 115.38 mph. You may recall we previously ran 12.25 in another test Shelby, but that one was broken in well, and the conditions were improved. In addition, we were fighting a 10- to 15-mph head wind that would stick with us the entire test day.
After giving the car a short cooldown, a second run was attempted. This time leaving at 4,500 rpm, the Shelby recorded a 12.510-second pass at 114.55 mph. The 60-foot time was nearly identical to the first run as the short time came in at a 2.018. When it ran another 12.51-second pass on its third effort in stock trim, we realized that due to a rise in ambient temperature the car would not come back to the 12.38 it ran early in the morning. In addition, it was difficult to launch on the stock tires.
"It was very difficult to find a happy medium between bogging the car and spinning the tires on the launch," Smith says. "It was hard to launch it above 4,500 rpm. If I just dropped the clutch, it would spin. On the other hand, with any less rpm, it would want to bog-bad. Side-stepping the clutch didn't seem to help our cause, but I eventually found something that would work. The 12.38 was a result of an extremely good launch."
With the last two runs within 8-thousandths of a second of each other, we handed the Shelby over to the JDM crew for the first stage of the bolt-on bonanza.
Hook, Line, and Sinker
The first bolt-on modification we tried was a fairly basic one as we swapped out the stock rear wheels and tires for a set of drag radials. The Shelby rides from the Flat Rock factory on P285/40ZR18 Goodyear F1 Supercar tires wrapped around 18x9.5-inch machined aluminum wheels. While the F1 Supercars are extraordinary all-around tires, we knew that more could be gained by switching to a set of drag racing- specific shoes.
So off came the factory rolling stock and on went a set of M&H Tires Racemaster drag radials. The new tires were mounted on a set of Cobra wheels that would fit the Shelby. The Racemasters are DOT-approved and feature an exclusive, sticky tread rubber and lightweight design. This makes them perfect for launching a car hard on the starting line and keeping the rear end planted. We wanted to have a decent-sized footprint for the car to leave on, so JDM ordered 325/45/R17 tires. The tire diameter itself was taller and the width of the Racemasters are bigger than the stock meats. After we bolted on the tires, Shaun Lacko of JDM torqued down the new rims and set the tire pressure to 16 psi. It was time to see what the drag radials could do for the Shelby.
As soon as the clutch was dropped, we knew there would be an improvement in performance. After recording a 1.949-second 60-foot time, the Shelby motored down track, stopping the timers in 12.36 seconds. The improved traction provided by the Racemasters allowed the Shelby to short-time better, resulting in the best elapsed time of the day up to that point (keep in mind the temperature was up about 15 degrees over the 12.38 with the stock tires). If we throw out the first run and look at the second and third runs, which were extremely close to one another, the tires lowered the elapsed time by about 0.150 seconds, a con-siderable amount.
Of interest with the tire change, however, was the lowered trap speed of the car. After running a best speed of 115.38, which was also recorded on the first pass of the day, the speed on the pass made with the car shod in the drag radials was down to 113.49. Even the speed marks on the 12.5-second passes were nearly a full tick higher. So why did the elapsed time improve while the speed dropped? The answer is as simple as looking at the numbers on the sidewall of the tire. With the taller tire, the effective gear ratio was changed slightly, and that, compounded with slightly worse air when compared to the earlier run, caused the speed to drop. Overall, however, the drag radials gave the Shelby the ability to hook harder on the starting line, thus improving our elapsed times.
All Tuned Up
Most factory fuel-injected cars, especially performance models such as the Mustang in general and the Shelby GT500 in particular, come with a conservative tune. This allows for a safe margin if you get a bad tank of gas, or if you decide to tow a trailer through the Arizona desert in mid-summer. Often, adding a degree or two of timing and trimming the fuel curve is worth some horsepower at the wheels. [Note: Modifying the factory tune almost always requires that 91-93 octane be used-Ed.] And while the 500hp mark associated with the GT500 is stout, we were certain there was still quite a bit of power left in the ECM.
While the car was cooling down after the fourth run-the one in which we ran our drag radial tire experiment-Jim D'Amore broke out the laptop and a blank SCT XCalibrator 2 tuner. He developed a custom tune that started off by raising the rev limiter, which allowed us to raise the shift points. Before, Smitty was sliding the shifter at 6,000 rpm. Now, he'd be rowing at a more aggressive 6,500 rpm. D'Amore then went into the fuel and timing maps, making some moves there as well.
"Within this area, I changed numerous things," he says. "The air/fuel ratio on the run before (run four) at 5,000 rpm was 12.7:1, which is on the lean side. To combat that, I changed the air/fuel ratio to 12.0:1 across the board from idle to 6,500. I also added a bit of timing to the timing curve, and have the coolant fans and intercooler pump turning on at a lower temperature."
With the new tune loaded, the Shelby was fired up and sent down the track for run number five. Once again launching at 4,500, the car 60-footed much better than the run before, recording a 1.834-second short time. Still equipped with the drag radials, the tune unlocked some power that showed up at the finish line as the Shelby broke into the 11-second zone with an 11.901-second, 116.88-mph shot. We then backed up that run with an 11.932/116.64 effort. With the air comparable to what it was when we tested the sticky tires alone, the slightly modified ECM showed an improvement of nearly one-half second over the already sizeable gain we saw with the tire swap. Talk about huge!
With drag radials helping us effectively get the power to the pavement and a custom tune that resulted in some hidden power, the time to free up the breathing of the Shelby was upon us. After the last pass with the new tune, Shaun Lacko of JDM jacked up the rear of the Shelby in preparation for the trackside exhaust install we had scheduled. Not everyone will go for headers and a cat-free exhaust, so we wanted to see what a simple after-cat exhaust would do. Allowing for sufficient cool-down before he wriggled his way under the specialty S197, Lacko replaced the stock exhaust with a MagnaFlow after-cat system.
The stock exhaust on the Shelby is, for a production car, pretty good in its own right. Featuring cast-iron exhaust manifolds and 2.5-inch-diameter pipes, the heart and soul of the system is the factory-installed x pipe system. While the stock exhaust is good, we were of the impression that it was still a bit restrictive. Enter the MagnaFlow piece.
The MagnaFlow system is a complete system that comes with mufflers, piping, and all neces-sary hardware. Made of stainless steel, the sys-tem is mandrel bent and comes with a pair of good-looking polished stainless steel tips. Even though the tubing diameter is the same as the stock system-2.5 inches-we expected an improvement due to the fact that the mufflers and tubing on the MagnaFlow system offered less restriction than the stock pieces. And, we'd be doing it right at the track, with basic hand tools, proving that anyone can do the swap in his or her own driveway. Only a few dragstrip passes would truly tell the tale, though, so once Lacko had everything buttoned up, we dropped the jack and then the clutch for three more runs.
When the Shelby flew through the finish line on the first pass with the exhaust, we were impressed with the result. After traveling 60 feet in 1.78 seconds-our best short time thus far-the Shelby ran an 11.831 at 117.03 mph. Backing that run up was another 11.8-second run, an 11.897 at 117.25. Just to be sure, we rode the steed one more time with the exhaust, running an even quicker 11.785 at 117.31. On that run, we recorded a 1.777 60-foot time.
With the air getting worse as the day progressed, the Shelby continued to pick up sizeable gains in performance. The exhaust dropped our elapsed times another tenth and a half, and we picked up almost a full tick on the speedometer. Obviously, the MagnaFlow after-cat system allowed the big mod motor to breathe easier. In addition, the exhaust seemed to add some low-speed torque to the Stang, as the 60-foot times improved by 5-hundredths of a second with no changes to launch rpm or procedure.
The Finish Line
We drove to the dragstrip in a bone-stock Shelby GT500 carrying hand tools, drag radials, a laptop and flash tuner, and an after-cat exhaust system. Six hours and several sets of dirty hands later, we turned the brutally fast SVT special into a 'Vette killer with a few basic bolt-ons. On the surface, these three bolt-ons (stickier tires, a tune, and an exhaust system) are something an everyday Mustang owner does to his or her car. In the case of the Shelby, these three modifica-tions turned the car into something that will pulverize anything it lines up against at the track. Starting off in the low- to mid-12-second zone, we ended up powershifting our way to an 11.78-second best, while improving trap speed from 115 mph to 117. If you break out the calculators and do the math, we dropped 0.595 second off of the Shelby's original elapsed time (0.730 second off of the back-to-back 12.5-second runs) while picking up nearly 2 mph. Not too bad for a day's work.
|Tale of the Times|
|When it comes to performance upgrades, the numbers don't lie. With each upgrade, you want to see a reduction in elapsed time and an increase in trap speed. Check out the numbers below. The results and potential of this beast are impressive. Note: Differences are from the baseline run first and previously performed modifications second.|
|Baseline Run: 12.380/115.38|
|Modification||Best ET/MPH||E.T. Difference||MPH Difference|