Estimated reading time: 4 minutes
One of the most fierce Mustangs ever produced is the modern Shelby GT500. What started as a 500 horsepower beast in 2007 evolved into a 662 horsepower, Earth-rotating muscle car by 2013. One commonality between all 2007-2014 GT500s is the intercooled and supercharged modular engine that’s boosted with a roots-style Eaton supercharger.
While virtually all Shelby Mustangs make great power, VMP Performance can help put your GT500 way ahead of the pack. To prove our point, we picked up a well-worn 2012 Shelby at a reasonable price. It has a few dings, but is mechanically sound. The plan is to show what it can do stock, then modify it for max power using only bolt-on parts.
The 2012 GT500 is a stout player producing 550 horsepower and 510 lb·ft of torque from the 5.4 L engine. Shelby GT500 Mustangs respond well to boost. We started with a VMP Gen2R blower and worked our way up to the mighty, all-new VMP Gen3 supercharger. We hoped to eclipse 800 horsepower at the wheels.
One of the benefits of the VMP blowers is that they are easy to install. In many cases, they can be directly swapped for an instant and easy power upgrade.
“In milder applications, the VMP Gen3, with Eaton’s new 2650 rotors, shines as well. We’re finding it moves a ton of air without needing to be spun hard,” said Justin Starkey, President of VMP Performance. “For the enthusiast looking to keep a stock engine alive for a long time, this means large pulley sizes, slower blower RPM, lower temps, and less chance of belt-slip issues.”
Before getting started, the 80,000-plus mile 2012 GT500 was strapped to the VMP Dynojet and a baseline test was performed. In stock trim, with 93-octane fuel in the tank, the 5.4 L engine produced 487 rear-wheel horsepower and 443 lb·ft of torque. This was using the stock intake, exhaust, and tune.
With a starting number in the bank, the hot rodding began. The VMP team unboxed and installed its Gen2R supercharger, along with a VMP 2.4 inch pulley, VMP TwinJet 67 mm throttle body, and a supporting cast of Brisk GR12YS spark plugs, a JLT Performance 123 mm Big Air cold-air intake, Ford 56 lb injectors, and the Mustang’s computer was flashed with a VMP calibration designed for these mods. The result was impressive, as the GT500 delivered
roughly 660 horsepower and 595 lb·ft of torque to the wheels. A healthy gain for sure, but the guys were just getting started.
The Gen2R blower was replaced with the all-new VMP 2.65 L Gen3 unit, along with a larger 3.0 inch pulley. Everything else was left alone and the GT500 still had 93-octane pump gas in the tank. The result from the simple swap was amazing. “With six pulley sizes larger, we made the same power, 661 hp and 595 torque, as the Gen2R,” said Starkey. “We made a ton of power without even trying and now we’re ready to try the smaller pulleys,” he added.
First up was a VMP 2.8 inch pulley. The smaller pulley increased boost level and increased power, with the GT500 now making 684 rwhp and 634 lb·ft of torque. That’s an extra 30 hp and 40 lb·ft of torque over the Gen2R at the same boost level.
Next was the smaller 2.6 inch pulley, which kicked the output up once more, to 695 horsepower and a torque number of 640 at the wheels. “We are knocking on the door of 700 at the tires,” said Starkey, “however, I feel the gains are starting to taper off a little bit.” He noted that the throttle body could be causing a restriction. “I want to try swapping on the VMP 160 mm throttle body because it’s specifically made for the VMP Gen3 TVS and we’ll see what it does.”
In the name of science, they switched back to the 3.0 inch pulley, and the Shelby made identical power (689 rwhp and 620 rwtq). Next the 2.8 inch pulley was put back into service. As a side note, a VMP fuel pump booster was added to ensure proper fuel was being delivered to the engine.
Justin felt it would top 700 rwhp, and he was spot on with the GT500 making 712 rwhp and 657 rear-wheel torque. So, if the 2.8 inch was good—you guessed it—they went for the 2.6 inch pulley.
The magic was taking place as horsepower jumped again, this time to 721 and torque climbed to 659 lb·ft at the wheels. Keep in mind, the GT500 was running within safe tuning parameters (14-15 degrees of timing) on 93-octane pump gas.
According to Justin, the situation changes with race gas, so the pump gas was traded for VP Racing Fuels C-16. Race fuel offers the opportunity to run more ignition timing for increase cylinder pressure, but without the worry of detonation. When properly tuned, this combination generally shows an increase in horsepower and torque. Justin loaded a new tune, to maximize performance with the race gas, and the GT500 was put to the test.
He lit the fire and the Shelby responded with 802 rear-wheel horsepower and 758 lb·ft of torque! That’s a gain of over 300 rear-wheel horsepower from stock and all with a factory lower pulley and untouched exhaust, including the manifolds, catalytic converters, and mufflers.
So, as you can imagine there’s power to be unleashed from the 5.4 L engine. All the information and supporting mod list can be seen in the supporting video. We know the GT500 has more ponies to be unleashed, and we asked you how to do it. The response was amazing. We’re looking at freeing up the exhaust with long-tube headers and a matching mid-pipe. Then, we’ll drop the pulley size down to the 2.6 inch and the 2.4 inch. Be sure to check back for the results!
