Steve Turner
Former Editor, 5.0 Mustang & Super Fords
December 26, 2013

In a world prowling with Coyotes, the 2013 Shelby GT500 stormed onto the Mustang scene as the undisputed bad boy. Packing 662 horsepower at the flywheel, sharp handling, and huge brakes, the Trinity 5.8-powered beast is an all-around performer that stands above its peers.

The uninitiated might assume it would be all the car you'd ever need. As we know, however, starting with the top dog only makes it more fun to start bolting on extra performance.

Since the Terminator days, factory supercharged Mustangs have responded better than any others to the most basic of bolt-ons, and that trend continues to this day. In fact, it seems the latest blown 'Stangs respond even better.

Among the most long-running purveyors of bolt-on performance is Steeda Autosports. The company is perhaps best known for its complete line of suspension and handling enhancements. However, Steeda offers a complete line of performance parts as well. When the company let us know it had developed a Power Pack for the '13-'14 Shelby GT500, we made a trip down to the company's Pompano Beach campus to see what kind of gains this package would offer.

The Power Pack includes a cold-air intake, a smaller supercharger pulley, and an SCT X3 with a custom tune. As you'll soon see, the gains were pretty impressive.

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On The Dyno

Baseline
CAI
Pulley
Baseline vs. Pulley>
RPM Power Torque Power Torque Power Torque Power Torque
2,300 216.78 494.96 230.88 527.07 256.94 586.70 40.16 91.74
2,400 231.31 506.19 243.84 533.58 271.07 593.18 39.76 86.99
2,500 243.81 512.19 259.90 545.98 286.08 600.98 42.27 88.79
2,600 257.59 520.33 273.69 552.86 299.12 604.25 41.53 83.92
2,700 271.64 528.40 287.67 559.57 311.65 606.20 40.01 77.80
2,800 281.50 528.04 300.55 563.77 324.77 609.18 43.27 81.14
2,900 294.24 532.88 314.41 569.37 338.45 612.96 44.21 80.08
3,000 306.13 535.91 327.74 573.77 351.93 616.11 45.80 80.20
3,100 319.96 542.10 341.21 578.07 364.42 617.41 44.46 75.31
3,200 329.21 540.30 353.31 579.88 379.56 622.92 50.35 82.62
3,300 338.53 538.79 366.07 582.63 395.09 628.82 56.56 90.03
3,400 350.82 541.92 379.63 586.41 411.31 635.34 60.49 93.42
3,500 362.11 543.38 394.56 592.06 425.27 638.16 63.16 94.78
3,600 373.24 544.54 407.85 595.03 438.96 640.40 65.72 95.86
3,700 385.59 547.32 419.90 596.04 453.88 644.28 68.29 96.96
3,800 402.05 555.66 434.28 600.23 465.06 642.76 63.01 87.10
3,900 409.16 551.04 445.59 600.07 478.85 644.84 69.69 93.80
4,000 417.06 547.62 459.66 603.54 494.39 649.16 77.33 101.54
4,100 426.92 546.88 471.72 604.30 506.79 649.21 79.87 102.33
4,200 440.49 550.85 484.18 605.46 509.94 637.67 69.45 86.82
4,300 447.76 546.90 497.20 607.27 521.25 636.67 73.49 89.77
4,400 455.59 543.81 510.87 609.81 533.70 637.07 78.11 93.26
4,500 467.48 545.62 522.45 609.79 544.08 635.02 76.60 89.40
4,600 479.77 547.79 533.78 609.45 551.26 629.40 71.49 81.61
4,700 490.49 548.11 540.33 603.80 563.60 629.83 73.11 81.72
4,800 497.47 544.34 550.95 602.85 571.67 625.52 74.20 81.18
4,900 508.44 544.98 554.17 594.00 577.60 619.12 69.16 74.14
5,000 519.58 545.77 563.78 592.23 586.78 616.36 67.20 70.59
5,100 518.90 534.39 567.25 584.16 591.22 608.88 72.32 74.49
5,200 520.80 526.03 578.29 584.10 599.18 605.18 78.38 79.15
5,300 533.06 528.24 585.11 579.82 604.75 599.28 71.69 71.04
5,400 535.11 520.46 593.92 577.66 610.77 594.04 75.66 73.58
5,500 546.83 522.20 595.20 568.37 619.33 591.45 72.50 69.25
5,600 531.38 498.37 599.06 561.86 622.56 583.88 91.18 85.51
5,700 533.85 491.91 601.50 554.24 624.20 575.15 90.35 83.24
5,800 545.59 494.04 607.73 550.32 633.61 573.76 88.02 79.72
5,900 553.68 492.87 610.89 543.82 639.72 569.47 86.04 76.60
6,000 554.17 485.10 616.13 539.35 642.09 562.05 87.92 76.95
6,100 569.26 490.14 617.39 531.59 647.24 557.28 77.98 67.14
6,200 566.75 480.11 618.38 523.85 652.98 553.15 86.23 73.04
6,300 570.20 475.35 625.58 521.54 658.50 548.98 88.30 73.63
6,400 568.69 466.70 629.89 516.93 653.12 536.00 84.43 69.30
6,500 n/a n/a 634.47 512.68 653.35 527.94 n/a n/a
6,600 n/a n/a 620.76 494.12 649.6 516.94 n/a n/a
6,700 n/a n/a n/a n/a 655.02 513.47 n/a n/a
6,800 n/a n/a n/a n/a 654.17 505.26 n/a n/a

We know that opening up the inlet and sharpening the tuning are tried-and-true methods to improve Mustang performance. The '13 Shelby GT500 likes these mods a lot. The power and torque gains come on in chunks and build across the entire powerband. Adding the smaller pulley simply expands on those gains with more substantial gains across the curve. The peak gains from the Power Pack were 102.33 lb-ft at 4,100 rpm and 91.18 horsepower at 5,600, but it's the movement of the entire curves that you feel in the seat of your pants.

"The '13 GT500 has some fundamental differences to previous models, but the basics are similar," Gus Irizarry said. "It seems Ford put together a powerful combination and had to dial it down in terms of horsepower and torque via torque and throttle limiting. With the previous models we didn't see as much limiting. The throttle limitations going on were one of the biggest things we had to solve, and once solved that alone unlocked a substantial amount of power."

As you can see, the addition of the Steeda CAI and custom tune produced the greatest gains across the entire curve, but boost with the smaller Steeda pulley was no slouch either. After our visit, long-tubes and a throttle body brought the peaks to 701.69 hp and 689.64 lb-ft.

Horse Sense: If you are a big fan of carbon fiber like this scribe, Steeda also offers its cold-air intake in real carbon fiber (PN 555-3168). It is functionally the same as the composite kit, but the carbon fiber unit is lighter and looks great. Of course, real carbon does carry a higher tariff at $469.95.