"I'll tell you one thing, there's nothing like building up an old automobile from scratch and wiping out one of these Detroit machines. That'll give you a set of emotions that'll stay with you. Know what I mean?"
Maybe we've watched Two-Lane Blacktop a few too many times, but we couldn't agree more with the maniacal and sleep-deprived character G.T.O. And to prove it, we've spent months modifying our long-term 2005 Mustang GT in an attempt to outperform Ford's 2007 Shelby GT500.
With 500 horsepower, the Shelby GT500 may be the king of all Mustangs, but the king don't come cheap. In fact, it's honkin' expensive. With a list price of $41,675 it costs nearly $20,000 more than we paid for our long-term 2005 Mustang GT. Not to mention that bringing home a GT500 today will set you back more like $75,000. Which got us thinking....
Why not build our own? So we did. Last week, in the article titled "Project Mustang GT vs. Shelby GT500, Part 1," we detailed the modifications we made to our Mustang GT. Modifications that totaled $13,063, which is more than we planned on spending, but still less than a new GT500, even when our Mustang's original sticker price is factored in.
Was it money well spent? Let's find out.
The contest
Our showdown between the 2007 Shelby GT500 and our own supercharged 2005 Ford Mustang GT became a weeklong three-stage contest of performance and endurance.
First we went to MD Automotive in Westminster, California, and ran both cars on its Dynojet chassis dyno to compare engine power. Then we headed to our usual test facility and ran them through our standard instrumented tests to compare handling, acceleration and braking.
Finally we got serious and headed for the Radical Loop at Spring Mountain Motorsports Ranch in Pahrump, Nevada. The Radical Loop is a 10-turn, 1.5-mile road-racing circuit with tight corners and relatively modest straightway speeds, so it's appropriate for evaluating street cars.
Spinning the rollers
On the dyno, the GT500 first put down 432 hp and 418 pound-feet of torque. After we discovered (following much wrangling with Ford) that our test car had been equipped with a faulty air filter, we returned to the dyno for a second test and the GT500 put down a healthy 448 hp and 420 lb-ft torque. Read our full test of the GT500 for all the details.
When we lashed the project Mustang to the dyno, it put down wildly erratic numbers because of rough combustion at high rpm, so peak power varied by as much as 30 hp. Something wasn't right, and we were puzzled because the problem wasn't obvious while driving the car on the street. We measured the air/fuel ratio — a telltale indicator of lean, potentially catastrophic tuning — and found it to be between 12.9:1 and 12.2:1 throughout the heart of the power band. Ideally, an air/fuel ratio in the range of 11.0:1 would be rich enough to eliminate lean surge, plus it would improve the engine's long-term durability by forestalling detonation.
It's possible that we weren't getting enough spark at this relatively extreme level of supercharger boost, since the project Mustang's spark plugs had been in place for 20,000 miles. It's also possible that Vortech's engine management system isn't tuned perfectly. Whatever the case, the most representative dyno run with our supercharged engine produced 376 hp and 353 lb-ft of torque. This is a 42-percent increase in horsepower from the stock engine's 265 hp, and a 28-percent increase in torque from the V8's initial 276 lb-ft. Even so, our car was a good bit off the GT500's power numbers.
The street
The addition of aftermarket hardware transformed our Mustang into a true man's machine. Crack the throttle and there's a mechanical symphony that's one-part supercharger whine and two-parts American V8 rumble. When you're in the driver seat, the Hurst shifter invites gear slamming, while the view over the hood scoop begs you to powerslide out of every corner. Even better, the power delivery is about as subtle as Grave Digger's freestyle performance at the Monster Jam World Finals, while there's enough cornering grip available to disorient a fighter pilot.
Our Mustang's ride quality, however, suffered in the transformation. We're forced to slow down on rough roads more than we'd like, and highway trips can be punishing. The low ride height also forces us to crawl the Mustang in and out of driveways.
By comparison, the GT500 is a pussycat. Very little exhaust noise seeps into the cabin and the ride is comfortable on the freeway. When you lay into the gas pedal, the thrust is abundant but manageable. The Shelby-ized Mustang also has enough ride height to clear speed bumps and negotiate steep driveways.
But the GT500 is fast. And easy to drive. This is going to be a close race.
The track
It wasn't a surprise when the GT500, with its larger 5.4-liter engine, beat our project car in the quarter-mile by a significant margin, making a pass in 12.8 seconds at 113 mph. In comparison, our GT, which only packs 4.6 liters, ran 13.3 seconds at 108 mph. Although our supercharged Mustang isn't as quick as the Shelby, this performance was 1 full second and 8 mph quicker than the stock Mustang GT's 14.3 seconds at 100 mph. Just for fun, we slapped on the drag radials and shaved another tenth of a second from its time, posting a pass in 13.2 seconds at 108 mph. Thanks to the drag-caliber BFGs, our car hit 60 mph in 4.6 seconds, equaling the GT500's best run.
With its six-speed manual, the GT500 also gets better fuel economy than our car, but if you care you're reading the wrong story.
Luckily, our GT fared better in the handling and braking tests, keeping alive our hopes of beating the GT500 on the track. Through the slalom, the GT beat the Shelby by 1 mph, recording 69.1 mph vs. 68.1 mph. This represented a huge improvement over the stock Mustang GT's pass through the slalom at 65.2 mph.
Our decision to fit the project Mustang with 275/40ZR18 BFGoodrich g-Force T/As paid off on the skid pad once we dialed in the damping and tweaked the antiroll bars. The modified GT circled at 0.96 g, while the Shelby GT500 managed just 0.89 g. Our project car also had an edge in braking performance, stopping in 112 feet while the Shelby required 117 feet. In comparison, the stock Mustang GT requires 129 feet to stop.
Getting radical
Spring Mountain's Radical road circuit combines a lot of decreasing-radius turns with one stomach-wrenching, negative-g drop-off plus a sphincter-checking blind crest. You don't want to drop a wheel off the pavement, since there are plenty of big rocks that will turn a lowered Mustang into scrap. Get it wrong here and you're going to regret it.
After about 20 laps to familiarize ourselves, we got serious and quickly discovered that the Shelby GT500 is a capable track machine. On smooth pavement, its handling behavior is free of any vices and the powerful brakes are always there for you. We turned hot laps one at a time so we never gave the Brembos a ruthless beating, but they returned consistent, reliable feedback every time we touched the brake pedal.
We were also impressed with the Shelby's composure at corner exit. Get into the throttle a little too early and you'll find yourself in a powerslide, but it's easily controllable. Overall, the Shelby GT500 impressed with its well-rounded capability on the track, where it felt just as at home as it does on the street.
Our project car, however, was even more at home on the track than the Shelby. Its on-the-deck ride height paid off as soon as we heeled over the car into the first corner. Compared to the Shelby GT500, our project Mustang turned in quicker, rotated more easily and delivered faster cornering speed.
And when we accelerated hard away from 2nd-gear corners, the project Mustang left the Shelby GT500 behind. We have to admit, though, that the project Mustang weighed just 3,573 pounds, some 330 pounds less than the 3,903-pound Shelby GT500.
Nobody's perfect
But all isn't perfect with our self-built admiral of the aftermarket.
When we tried to string together five hot laps, the hot-rod Mustang pegged its water temperature gauge and we had to back off. And although the Mustang GT's upgraded brakes represent a lot of performance improvement in a single stop, they aren't up to the task of repeated hot laps. To be fair, the Hawk HPS brake pads we acquired from Stoptech are not meant to be a track-caliber pad. If we were really intent on building our Mustang GT into a track car, we'd need larger rotors, harder pads and even more powerful calipers.
When we tallied the quickest laps, the Mustang GT came out on top by more than a second, recording 1:26.60 vs. the Shelby GT500's 1:27.65. Though the Mustang GT's straightaway speed is 3.5 mph slower than that of the GT500, its speed in the corners made up the difference in the lap time. This result comes with a caveat, however, because we conducted road-course testing when our Shelby GT500's power was compromised by an air filter that was delaminating. (See our GT500 full test.)
The story that's best told without numbers is the sound made by our project Mustang. It announces its presence with a guttural rumble thanks to its Magnaflow exhaust. If you like to hear the engine, this is the right way to go with an aftermarket exhaust. In comparison, no one will turn a head when the Shelby GT500 pulls up. Of course there's a reason for this, as our car is 2 decibels louder at idle than the Shelby, 7 decibels louder during full-throttle acceleration and 13 decibels louder while cruising at 70 mph.
You decide
So the only issue we really had with our project Mustang GT involved long runs on the racetrack. But it shouldn't be a major surprise that a Mustang GT fitted with a number of aftermarket parts will lack the durability quotient of a factory-engineered hot rod. Even so, the capacity of the cooling system seemed to be the problem, something that could easily be fixed.
This we could have told you before the test. What we wouldn't have predicted is that our aftermarket-equipped Mustang could be this much fun for about $3,600 less than the MSRP of a GT500 — or about $25 grand less than a Shelby GT500's current selling price. And for all but our run on the racetrack (conducted in brutally hot weather), our project car has proven itself perfectly reliable in street driving. The stock 22,000-mile-old clutch and differential were more than up to the additional power and grip, even when we used drag-strip-ready BFG tires.
So we didn't exactly wipe out the Shelby GT500 as we had originally planned, but we did have a great time trying. Anybody want to buy a slightly used, supercharged 2005 Mustang GT? Stock parts go with it, but it may need new rear tires. Any reasonable offer accepted.
Parts Cost:
Sources
Chassis Dyno Services
MD Automotive, Westminster, California
www.markdibella.com
(714) 891-1113
Axis Reverb wheels: 18x8.5, 40mm offset, 5x114 bolt pattern
Axis Wheels
www.axiswheels.com
(562) 906-9898
Magnapack exhaust system
Magnaflow
www.magnaflow.com
(800) 824-8664
Antiroll bars
Progress Technology
www.progressauto.com
(714) 575-1193
Ducktail spoiler
Classic Design Concepts
www.classicdesignconcpets.com
(248) 624-7997
Pro Kit lowering springs
Eibach Springs
www.eibach.com
(800) 507-2338
GTR ram-air hood
RK Sport
www.rksport.com
(800) 214-8030
D-Spec dampers
Tokico Gas Shocks
www.tokicogasshocks.com
(800) 548-2549
BFGoodrich g-Force T/A (275/40R18) and g-Force T/A Drag radials (295/35R18 or 315/30R18)
BFGoodrich Tires
www.bfgoodrichtires.com
(877) 788.8899
Steeda chromoly trailing arms and adjustable third link
Steeda Autosports
www.steeda.com
(954) 960-0774
Vortech high-output supercharger system
Vortech Engineering
www.vortechsuperchargers.com
(805) 247-0226
Hurst shifter
Summit Racing Equipment
www.summitracing.com
(800) 230-3030
8-inch fixed black antenna
American Muscle
Americanmuscle.com
(888) 782-6448
Maybe we've watched Two-Lane Blacktop a few too many times, but we couldn't agree more with the maniacal and sleep-deprived character G.T.O. And to prove it, we've spent months modifying our long-term 2005 Mustang GT in an attempt to outperform Ford's 2007 Shelby GT500.
With 500 horsepower, the Shelby GT500 may be the king of all Mustangs, but the king don't come cheap. In fact, it's honkin' expensive. With a list price of $41,675 it costs nearly $20,000 more than we paid for our long-term 2005 Mustang GT. Not to mention that bringing home a GT500 today will set you back more like $75,000. Which got us thinking....
Why not build our own? So we did. Last week, in the article titled "Project Mustang GT vs. Shelby GT500, Part 1," we detailed the modifications we made to our Mustang GT. Modifications that totaled $13,063, which is more than we planned on spending, but still less than a new GT500, even when our Mustang's original sticker price is factored in.
Was it money well spent? Let's find out.
The contest
Our showdown between the 2007 Shelby GT500 and our own supercharged 2005 Ford Mustang GT became a weeklong three-stage contest of performance and endurance.
First we went to MD Automotive in Westminster, California, and ran both cars on its Dynojet chassis dyno to compare engine power. Then we headed to our usual test facility and ran them through our standard instrumented tests to compare handling, acceleration and braking.
Finally we got serious and headed for the Radical Loop at Spring Mountain Motorsports Ranch in Pahrump, Nevada. The Radical Loop is a 10-turn, 1.5-mile road-racing circuit with tight corners and relatively modest straightway speeds, so it's appropriate for evaluating street cars.
Spinning the rollers
On the dyno, the GT500 first put down 432 hp and 418 pound-feet of torque. After we discovered (following much wrangling with Ford) that our test car had been equipped with a faulty air filter, we returned to the dyno for a second test and the GT500 put down a healthy 448 hp and 420 lb-ft torque. Read our full test of the GT500 for all the details.
When we lashed the project Mustang to the dyno, it put down wildly erratic numbers because of rough combustion at high rpm, so peak power varied by as much as 30 hp. Something wasn't right, and we were puzzled because the problem wasn't obvious while driving the car on the street. We measured the air/fuel ratio — a telltale indicator of lean, potentially catastrophic tuning — and found it to be between 12.9:1 and 12.2:1 throughout the heart of the power band. Ideally, an air/fuel ratio in the range of 11.0:1 would be rich enough to eliminate lean surge, plus it would improve the engine's long-term durability by forestalling detonation.
It's possible that we weren't getting enough spark at this relatively extreme level of supercharger boost, since the project Mustang's spark plugs had been in place for 20,000 miles. It's also possible that Vortech's engine management system isn't tuned perfectly. Whatever the case, the most representative dyno run with our supercharged engine produced 376 hp and 353 lb-ft of torque. This is a 42-percent increase in horsepower from the stock engine's 265 hp, and a 28-percent increase in torque from the V8's initial 276 lb-ft. Even so, our car was a good bit off the GT500's power numbers.
The street
The addition of aftermarket hardware transformed our Mustang into a true man's machine. Crack the throttle and there's a mechanical symphony that's one-part supercharger whine and two-parts American V8 rumble. When you're in the driver seat, the Hurst shifter invites gear slamming, while the view over the hood scoop begs you to powerslide out of every corner. Even better, the power delivery is about as subtle as Grave Digger's freestyle performance at the Monster Jam World Finals, while there's enough cornering grip available to disorient a fighter pilot.
Our Mustang's ride quality, however, suffered in the transformation. We're forced to slow down on rough roads more than we'd like, and highway trips can be punishing. The low ride height also forces us to crawl the Mustang in and out of driveways.
By comparison, the GT500 is a pussycat. Very little exhaust noise seeps into the cabin and the ride is comfortable on the freeway. When you lay into the gas pedal, the thrust is abundant but manageable. The Shelby-ized Mustang also has enough ride height to clear speed bumps and negotiate steep driveways.
But the GT500 is fast. And easy to drive. This is going to be a close race.
The track
It wasn't a surprise when the GT500, with its larger 5.4-liter engine, beat our project car in the quarter-mile by a significant margin, making a pass in 12.8 seconds at 113 mph. In comparison, our GT, which only packs 4.6 liters, ran 13.3 seconds at 108 mph. Although our supercharged Mustang isn't as quick as the Shelby, this performance was 1 full second and 8 mph quicker than the stock Mustang GT's 14.3 seconds at 100 mph. Just for fun, we slapped on the drag radials and shaved another tenth of a second from its time, posting a pass in 13.2 seconds at 108 mph. Thanks to the drag-caliber BFGs, our car hit 60 mph in 4.6 seconds, equaling the GT500's best run.
With its six-speed manual, the GT500 also gets better fuel economy than our car, but if you care you're reading the wrong story.
Luckily, our GT fared better in the handling and braking tests, keeping alive our hopes of beating the GT500 on the track. Through the slalom, the GT beat the Shelby by 1 mph, recording 69.1 mph vs. 68.1 mph. This represented a huge improvement over the stock Mustang GT's pass through the slalom at 65.2 mph.
Our decision to fit the project Mustang with 275/40ZR18 BFGoodrich g-Force T/As paid off on the skid pad once we dialed in the damping and tweaked the antiroll bars. The modified GT circled at 0.96 g, while the Shelby GT500 managed just 0.89 g. Our project car also had an edge in braking performance, stopping in 112 feet while the Shelby required 117 feet. In comparison, the stock Mustang GT requires 129 feet to stop.
Getting radical
Spring Mountain's Radical road circuit combines a lot of decreasing-radius turns with one stomach-wrenching, negative-g drop-off plus a sphincter-checking blind crest. You don't want to drop a wheel off the pavement, since there are plenty of big rocks that will turn a lowered Mustang into scrap. Get it wrong here and you're going to regret it.
After about 20 laps to familiarize ourselves, we got serious and quickly discovered that the Shelby GT500 is a capable track machine. On smooth pavement, its handling behavior is free of any vices and the powerful brakes are always there for you. We turned hot laps one at a time so we never gave the Brembos a ruthless beating, but they returned consistent, reliable feedback every time we touched the brake pedal.
We were also impressed with the Shelby's composure at corner exit. Get into the throttle a little too early and you'll find yourself in a powerslide, but it's easily controllable. Overall, the Shelby GT500 impressed with its well-rounded capability on the track, where it felt just as at home as it does on the street.
Our project car, however, was even more at home on the track than the Shelby. Its on-the-deck ride height paid off as soon as we heeled over the car into the first corner. Compared to the Shelby GT500, our project Mustang turned in quicker, rotated more easily and delivered faster cornering speed.
And when we accelerated hard away from 2nd-gear corners, the project Mustang left the Shelby GT500 behind. We have to admit, though, that the project Mustang weighed just 3,573 pounds, some 330 pounds less than the 3,903-pound Shelby GT500.
Nobody's perfect
But all isn't perfect with our self-built admiral of the aftermarket.
When we tried to string together five hot laps, the hot-rod Mustang pegged its water temperature gauge and we had to back off. And although the Mustang GT's upgraded brakes represent a lot of performance improvement in a single stop, they aren't up to the task of repeated hot laps. To be fair, the Hawk HPS brake pads we acquired from Stoptech are not meant to be a track-caliber pad. If we were really intent on building our Mustang GT into a track car, we'd need larger rotors, harder pads and even more powerful calipers.
When we tallied the quickest laps, the Mustang GT came out on top by more than a second, recording 1:26.60 vs. the Shelby GT500's 1:27.65. Though the Mustang GT's straightaway speed is 3.5 mph slower than that of the GT500, its speed in the corners made up the difference in the lap time. This result comes with a caveat, however, because we conducted road-course testing when our Shelby GT500's power was compromised by an air filter that was delaminating. (See our GT500 full test.)
The story that's best told without numbers is the sound made by our project Mustang. It announces its presence with a guttural rumble thanks to its Magnaflow exhaust. If you like to hear the engine, this is the right way to go with an aftermarket exhaust. In comparison, no one will turn a head when the Shelby GT500 pulls up. Of course there's a reason for this, as our car is 2 decibels louder at idle than the Shelby, 7 decibels louder during full-throttle acceleration and 13 decibels louder while cruising at 70 mph.
You decide
So the only issue we really had with our project Mustang GT involved long runs on the racetrack. But it shouldn't be a major surprise that a Mustang GT fitted with a number of aftermarket parts will lack the durability quotient of a factory-engineered hot rod. Even so, the capacity of the cooling system seemed to be the problem, something that could easily be fixed.
This we could have told you before the test. What we wouldn't have predicted is that our aftermarket-equipped Mustang could be this much fun for about $3,600 less than the MSRP of a GT500 — or about $25 grand less than a Shelby GT500's current selling price. And for all but our run on the racetrack (conducted in brutally hot weather), our project car has proven itself perfectly reliable in street driving. The stock 22,000-mile-old clutch and differential were more than up to the additional power and grip, even when we used drag-strip-ready BFG tires.
So we didn't exactly wipe out the Shelby GT500 as we had originally planned, but we did have a great time trying. Anybody want to buy a slightly used, supercharged 2005 Mustang GT? Stock parts go with it, but it may need new rear tires. Any reasonable offer accepted.
Parts Cost:
| Part | Cost |
|---|---|
| Blower | $5,305 |
| Antiroll bars | $478 |
| Hood | $700 |
| Rear spoiler | $395 |
| Springs | $210 |
| JDampers | $750 |
| Shifter | $200 |
| Wheels | $1,400 |
| Chromoly trailing arms | $210 |
| Adjustable third link | $125 |
| Brake pads | $170 |
| Tires | $964 |
| Exhaust | $600 |
| Hood pins | $15 |
| Antenna | $20 |
| Labor | |
| Alignment, wheel/tire mounting | $221 |
| Paint/hood pin labor | $300 |
| Supercharger install | $1,000 |
| Total | $13,063 |
Sources
Chassis Dyno Services
MD Automotive, Westminster, California
www.markdibella.com
(714) 891-1113
Axis Reverb wheels: 18x8.5, 40mm offset, 5x114 bolt pattern
Axis Wheels
www.axiswheels.com
(562) 906-9898
Magnapack exhaust system
Magnaflow
www.magnaflow.com
(800) 824-8664
Antiroll bars
Progress Technology
www.progressauto.com
(714) 575-1193
Ducktail spoiler
Classic Design Concepts
www.classicdesignconcpets.com
(248) 624-7997
Pro Kit lowering springs
Eibach Springs
www.eibach.com
(800) 507-2338
GTR ram-air hood
RK Sport
www.rksport.com
(800) 214-8030
D-Spec dampers
Tokico Gas Shocks
www.tokicogasshocks.com
(800) 548-2549
BFGoodrich g-Force T/A (275/40R18) and g-Force T/A Drag radials (295/35R18 or 315/30R18)
BFGoodrich Tires
www.bfgoodrichtires.com
(877) 788.8899
Steeda chromoly trailing arms and adjustable third link
Steeda Autosports
www.steeda.com
(954) 960-0774
Vortech high-output supercharger system
Vortech Engineering
www.vortechsuperchargers.com
(805) 247-0226
Hurst shifter
Summit Racing Equipment
www.summitracing.com
(800) 230-3030
8-inch fixed black antenna
American Muscle
Americanmuscle.com
(888) 782-6448
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