Marc Christ
Brand Manager, Modified Mustangs & Fords
September 26, 2012

Cold-air kits, throttle bodies, pulleys, and tunes are routine alterations amongst '07-up Shelby GT500 owners. These are reasonably priced pieces that are relatively easy to install, and for the most part, don't kill driveability. For years, Shelby owners have been able to add a couple of parts and boost output by 50-100 rwhp with ease, while maintaining the gracious grunt that give Shelby's their street prowess. But the recently released '13 Shelby GT500 is essentially a pre-modded GT500 right from Dearborn.

With a 662hp rating, this 2.3L TVS-blown 5.8-liter behemoth is ready to rock 'n' roll as is. Add in the massive brakes, leather-and-Alcantara-wrapped Recaros, and a top-speed of 200 mph, and this is not only the most powerful production Mustang ever, but also the most sophisticated--it even has built-in Launch Control.

So with Ford and SVT seemingly leaving nothing left on the table, how do we as enthusiasts improve on this already-stellar contraption? To find out, we headed to VMP Tuning in Deltona, Florida. Owner and tuner Justin Starkey had just taken delivery of his black coupe two days earlier, and managed to put just under 200 miles on the odometer before we started our adjustments.

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We had already seen others make drastic modifications to one of these beauties in the name of e.t.'s, but let's face the reality--that ruins the purpose for which this car was built. Besides, how many '13 GT500 owners are going to mod theirs out into a drag-only car? What we really want are ways to make SVT's newest Snake a more-capable version of itself.

So with Starkey in agreement, we decided to try the old-faithful quartet of CAI, throttle body, pulley, and tune. And not just the biggest, most racy components either, but rather run-of-the-mill bolt-ons that almost anyone would jump on. For the cold-air, we opted for JLT Performance's '10-'12 127mm carbon fiber kit (PN CFCAI127-GT500-10; $469); for the throttle body, we chose Ford Racing Performance Parts' dual-65mm Cobra Jet throttle body (PN M-9926-CJ65; $689.95).

Since SVT equipped its newest Shelby with a tiny 2.8-inch pulley making 12 pounds of boost, a smaller pulley for Eaton's 2.3L TVS is not readily available. To fill the void, VMP is now producing a 2.4-inch stainless steel version (PN VMP24-2013; $199.99) for '13 GT500 owners. VMP even makes its own pulley removal and installation tool (PN VMP3TOOL; $139.99), which we used to perform the swap.

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Making Mods

To achieve a baseline, Starkey strapped his new Shelby to VMP's in-house Dynojet. Once achieving normal operating temp of 175 degrees, he rolled on the throttle and spun the monster Four-Valve to redline. The result was an impressive 608 rwhp and 609 lb-ft of torque--stock. Using SCT software, Starkey then began altering the calibration. After a few pulls, he had maximized the tune. Another pull on the Dynojet yielded 631 rwhp and 641 lb-ft of torque--a 23 rwhp and 32 lb-ft gain.

Next up was the JLT cold-air kit. Though the kit is made for '10-'12 GT500s, the fitment is close. Starkey removed the stock CAI and dropped the JLT pieces in place. The shield, however, hit the new, larger intercooler pump. To solve this, Starkey removed the bolt holding the pump to the bracket. He moved the pump to the other side of the bracket and reinstalled the bolt. This allowed just enough room for the shield to slide into place. JLT says it's working on a kit specifically for the '13. After modifying the tune for the CAI, Starkey spun the rollers again. The result was 637 rwhp and 640 lb-ft of torque.

Reducing the restriction before the throttle body was an improvement, but we suspected the throttle body itself was an even larger restriction. After Starkey installed the larger twin-65mm FRPP throttle body, he reinstalled the JLT cold-air kit, adjusted the tune, and spun the rollers yet again. The result was 659 rwhp and 645 lb-ft of torque--a gain of another 22 rwhp and 5 lb-ft of torque.

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Ready to see how the engine would respond to more boost with the bolt-ons, Starkey installed his new 2.4-inch blower pulley. He monitored the vitals to make sure no other changes were necessary and made another pull. Boost jumped from 12 psi to 14 psi, and power output was up to 679 rwhp and 702 lb-ft of torque.

Though the 71 hp and 93 lb-ft increase was impressive for a couple of bolt-ons, we wanted more. Starkey added five gallons of Shell URT 100 unleaded race fuel, cranked the timing up a bit, and spun the rollers on the Dynojet. The result was 700 rwhp and 713 lb-ft.

Now up 92 hp and 114 lb-ft, this new Shelby is a whole new animal--but the nature of the beast remains. You really don't have to ruin driveability to reap the benefits of modifications after all--especially when you're starting with such a great product as the '13 GT500.

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