5.0 Mustang & Super FordsHow To Engine
Shelby GT500 Stealth Bolt-Ons - The Invisible
You'd Never Guess That VMP Tuning Gave Us 607 RWHP With A Pulley And A Tune
Horse Sense: Longtime readers might recall the last name Starkey, as Justin's lovely wife, Rebecca, is a former 5.0&SF Babe of the Month and Babe of the Year winner.
There are typically two schools of car guys. Some like as much flash as they can possibly get, while the other group likes to run softly and carry a big dyno number. Of course, there are a few like me who have to be difficult and like a little bit of each. Whatever your automotive addiction is, I'm fairly sure that you occasionally run across a product or service that you just have to have. You don't really need it, but you want it, and right away. Such was the case when I discovered VMP Tuning's Stock-Look 2.65-inch supercharger pulley for the Shelby GT500.
I knew I wanted one immediately. As much as I tried to make due with my already ample power, the call of more was too hard to resist. The fact that this pulley resembles the stock pulley was what really sealed the deal. There are plenty of flashy pulleys around that fit the stock blower and the FRPP TVS that's on my car ("Vapor Pressure," Sept. '08, p. 136), but this one blends right in. An unsuspecting passerby would never guess that my ride is packing more power thanks to its presence. I just love that.
Better yet, VMP's main man Justin Starkey has become one of the leading GT500 tuners working with Ford Racing Performance Parts' supercharger upgrade for the latest Shelby. Justin's own TVS'd GT500 has laid down a best dyno run of 705 hp and 708 lb-ft of torque at the rear wheels using this 2.65 pulley, Innovators West's 10-percent overdriven damper, VMP's115mm mass air housing, a big throttle body, FRPP short-tube headers, a free-flowing X-shape crossover, and Justin's own SCT tuning acumen. It was a lot easier putting my baby under the knife knowing that Justin has mastered these combinations.
With that said, all it took was the hint of an invitation from Justin and I was rolling up Interstate 4 in Project Vapor Trail to feed my power hunger. We also upgraded the intercooler's cooling system to compensate for increased heat of the additional boost. As you can see from the photos, the swap is fairly straightforward, and the results are impressive. Suffice it to say, the gains are as big as the grin on my face when I stand on it, and the car still drives like a dream.
Here are the parts that we added to PVT. The main players are VMP Tuning's VMP 2.65-inch Stock-Look pulley and 90mm idler package ($215), an SCT X-Calibrator V3 ($399), an Afco GT500 Pro-Series dual-pass heat exchanger from Lethal Performance ($399), and a Moroso GT500 Intercooler reservoir tank from Lethal Performance ($314.99). With more boost, a custom tune, and a more efficient intercooler system, PVT is set for more power and more consistency.
Here's how PVT's engine compartment looked when I picked it up at Classic Design Concepts ("Fortunate Sun," Oct. '08, p. 128) and drove it home, a huge smile on my face and the sun shining on my head. When we last dyno'd her at AFM, she put down 560 hp and 523.93 lb-ft of torque to the rear wheels, but more on that later. You'd think that would be enough, but VMP Tuning made the prospect of more power too tempting to resist.
Here Justin Starkey of VMP Tuning is working his magic on PVT. He started out baselining the car and datalogging key information such as the air/fuel ratio, engine load, mass air voltage, and more. On a car with a familiar combo, he starts with a base file he already created and tweaks it to maximize the results for the car at hand. It was amazing to watch him work his way through the SCT datalogging and tuning software screens and Dynojet screens with his touchscreen stylus. In a matter of minutes, he crafted a custom base tune for the FRPP blower on PVT. As you'll see in the On the Dyno sidebar, the tune alone made a big difference.
Begin by removing the plug from the front of the stock pulley. A seal holds it in place, so you'll have to cut around the perimeter of the plug with a razor or knife, then it pop out with something. Once it's started, you can thread it out like a bolt.
Use a ratchet with a flex-head attachment to loosen the stock tensioner and pop the blower belt off the pulley before you get down to business. Justin prefers the puller from Auto Specialties Performance because it grabs onto the ribs of the pulley for more grip without damaging it. The $129 ASP kit also includes the tool to install pulleys, so you can remove and install stock and aftermarket ones.
This is the coolest. On the left is VMP's Stock-Look 2.65-inch pulley; at right is the stock pulley from the FRPP TVS supercharger. VMP's pulley is a one-piece steel unit just like the stocker and features the same honed finish as the stock pulley on the bore, so it installs easily without overstressing the installation hardware. The VMP pulley fits the stock and FRPP blowers, but the stock blower pulley is 3 inches in diameter. The FRPP pulley is actually smaller at just over 2.9 inches.
While the puller pushes against the blower shaft to remove the pulley, the installer threads into the blower snout; then slides the pulley into place by turning the wrenches in opposite directions. In less than 10 minutes, Justin removed PVT's stock pulley and slid on the VMP 2.65. Even though he has a lot of practice, it goes to show you can easily reinstall the stock pulley if you are so inclined.
It was tough to get a camera in for the installation. The VMP Stock-Look 2.65 pulley requires the use of a larger 90mm idler pulley (left) to take up the slack in the stock blower belt. Although you have to squeeze in to unbolt the stock idler, it's no big deal. The VMP idler comes with a longer bolt, and its flat-black finish blends right in to retain the stealth of the Stock-Look pulley. While there are plenty of add-on tensioners on the market, Justin says he's never experienced belt-slip on his or a customer's car using the larger direct-replacement idler.
Can you tell the difference? Unless you look at the two pulleys side by side, it is tough. The VMP Stock-Look pulley is good for 3-4 pounds of boost on the stock blower and 1-2 pounds on an FRPP TVS.
Any time you increase the boost on a supercharged engine, you are going to introduce more heat into the air intake. Since GT500s are prone to heat-soaking with a stock blower, we knew our TVS with the 2.65 was ripe for an improved intercooler system. At the suggestion of our pal Jared Rosen of Lethal Performance, I decided to step up to Afco's dual-pass heat exchanger. To add this piece, Justin removes the front bumper cover, drains the intercooler coolant, and unbolts the stock heat exchanger.
It's easy to see that Afco's unit is taller and thicker than the stock heat exchanger. In fact, it's 3 inches taller and 3/4 inch thicker, even though it is slightly narrower than the stock one. Afco says its unit offers a 135-percent increase in overall surface area over the stock heat exchanger, and its more efficient double-pass design could be worth up to 60 hp over stock thanks to the cooler intercooler fluid temps.
The Afco heat exchanger is a really slick piece. The mounting brackets and the brackets for the stock intercooler pump are welded onto the heat exchanger. Just swap on your stock pump and attach the included hose. The hose is necessary since Afco's unit has its inlet and outlet fittings on the same side. The coolant passes through the heat exchanger twice before returning back to the engine compartment.
Furthermore, the Afco unit bolts directly in place of the stock unit and doesn't require removing the critical air flaps that direct air over the heat exchanger instead of letting it escape around the edges. As you can see, the pump sits in the stock location and everything fits just as it should.
While we were adding cooling capacity and the system was drained, it seemed like a good idea to add the new GT500 intercooler reservoir tank from Moroso. This swanky aluminum tank boosts reservoir capacity from a miniscule 1 1/2 quarts to nearly a gallon, which further allows the intercooler system to stave off heat and allow your GT500 to provide power more consistently. We know how sensitive these cars are to heat soak. It also features a fuel-cell-style cap and a petcock to drain it, so you can load the tank up with ice at the track or dyno; then revert back to just fluid for the street. (A warning-you do have to trim the hose from the tank to the intake manifold to make it fit.) The Moroso tank comes in a sweet raw-aluminum finish, but as you can see, our pal Allen Colding painted this one Vapor Silver to match PVT, which is a preview of the engine detailing to come in future issues. We topped off our mix of Peak antifreeze and distilled water with a bottle of Royal Purple's Purple Ice, which is said to improve the cooling capabilities of the coolant.
If you have been following the saga of Project Vapor Trail through its infancy, you know we last hit the dyno with this '08 Ford Shelby GT500 when it was still at the delivering dealer, Anderson Ford Mercury, parent of Anderson Ford Motorsport. There it received the FRPP SuperPack upgrade and SVT1 mufflers, and it laid down an impressive 560 rwhp. That was in late March, and it was still fairly cool-especially by Florida standards.
It isn't too much of a surprise that we had slightly different results in late May in Florida. PVT was down about 20 hp even though it was up 3 lb-ft of torque. All that really changed between AFM and VMP is that the car put on about 1,700 miles and had its first oil change. We've come to expect variances with weather and dynos, but we conferred with Justin Starkey for his thoughts on the difference. He explained that GT500 power numbers swing widely based on timing, which is influenced by air temperature, and that 1 degree of timing can have a pronounced affect. Also, the Dynojet software's SAE correction factor can't compensate for slight changes in boost due to air density changes or timing changes due to air temperature differences.
Still, Justin views the correction factor as a good guide to differing dyno numbers. "Overall air conditions were poorer at my shop. Given the higher correction factor, the higher temps resulted in lower numbers," Justin explains. "An SAE correction factor, in my opinion, can be largely viewed like a density altitude number, whereas a lower correction factor value means better overall air conditions, just like a lower density altitude number."
On to our new numbers. Justin started by baselining and learning what our Spanish Oak processor was up to. Then he quickly created a new tune file for our existing combo, as we wanted to see what just a tune was worth before we swapped the pulley. The result was an impressive jump of 33.91 hp and 30.39 lb-ft of torque at the tire. Keep in mind that the graph has more resolution (data points) than our charts, but we like to show both so you can see how things change across the whole rpm range.
Moving onto the Stock-Look 2.65-inch pulley, Justin again worked his magic on the keyboard to give PVT's boosted 5.4 just what it wanted while keeping the air/fuel ratio locked at a safe level. Remember-higher numbers are leaner and lower numbers are richer. Justin likes to keep the air/fuel in the safe 11.75:1-12:1 range.
With the pulley on, the car picked up boost across the board. Combined with the new tune, PVT picked up another 32.98 hp and 43.94 lb-ft of torque. When compared to PVT's baseline with the out-of-the-box FRPP blower and Pro-Cal tune, that's a gain of 66.89 hp and 74.33 lb-ft of torque.
The car is simply an animal now, but it drives even better than stock. Better yet, only 5.0&SF readers know all that extra power is there!