Muscle Mustangs & Fast Fords
Supercharger Shootout - Brothers In Arms
In This Supercharged Slugfest, We Find Out What 20 PSI Of Boost Is Worth On An '03 Cobra, An '05 GT, And A Shelby GT500.
Given the current crop of Blue Oval bruisers, it's easy to understand why Ford enthusiasts are so excited. When Ford and Shelby got together and introduced the GT500, the rest of the performance world stood up and took notice. The predecessor of this potent Pony was the aptly named Terminator. Both super stallions offer factory forced induction, but which one is the most potent?
Sure, the stock GT500 takes top honors in terms of displacement and rated power output, but what happens when you modify it? If money was no object, we'd all be driving Ford GT supercars, but since most of us have yet to locate that money tree, the reality is that every penny counts. With that in mind, we decided to include the not-so-supercharged bread-and-butter S197 GT in this shootout.
With its Three-Valve heads, the latest 4.6L motor took a turn away from the less-impressive Two-Valve PI motors of old, while simultaneously offering near-Four-Valve Cobra power numbers. Toss in a dose of variable cam timing and you have the makings of a giant-killer, especially after being treated to the same supercharger applied to the Terminator and GT500.
The question we hoped to answer with this comparison was simple. If supplied the same amount of boost pressure from the same supercharger kit, which combination offered the most power--the 5.4L GT500, the 4.6L Terminator, or the current 4.6L Three-Valve GT motor?
Before you get all up in arms about the big motor having the advantage, know that (like its owners) the Terminator motor backs down to no one. Despite the displacement deficit of nearly one full liter, the Terminator responds to bolt-ons like nothing we've ever seen before. That the all-aluminum mod motor (and overall vehicle) is considerably lighter than the GT500 makes it even more attractive.
While both the Cobra and the GT500 sport four valves per cylinder, don't count out the little Three-Valve motor. What it lacks in displacement or valve count, it makes up for in static compression and variable cam timing. These attributes aren't shared by the Four-Valve contingent, but it must be stressed that the stock Three-Valve rotating assembly wouldn't stand up to the abuse of 20 psi of twin-screw boost without modifications. Given the missing eight valves and normally aspirated origins, we decided to help out the Three-Valve GT motor with a boost-friendly rotating assembly. In went a Cobra crank, forged rods, and stock-compression pistons courtesy of Sean Hyland Motorsport that would allow us to safely crank up the boost on the Kenne Bell blower.
To answer this question, we gathered a stock GT500, an '03 Terminator, and an '05 GT, and subjected them to the rigors of boost. More specifically, all three motors were subjected to exactly 20 psi of boost pressure from the same 2.8L twin-screw supercharger from Kenne Bell. The 2.8L H-series blower was selected for its ability to supply the desired power and boost potential to each combination.
Since we fully expected the combinations to exceed 700 rwhp at 20 psi, we needed a blower that was both capable and comfortable (meaning efficient) at this power/boost level. The 2.8L twin-screw supercharger fit the bill, and Kenne Bell offers both upgrade kits for the Terminator and GT500 motors as well as a complete kit for the Three-Valve.