Horse Sense: We aren't showing an interior photo of Kenne Bell's GT 500 prototype because it's completely stock. But maybe we should have, as the car was delivered with one chrome air vent on the driver side, and three black air vents at dash center and on the passenger side. There's a fix from Ford, but we'd keep this snafu as a mark of individuality-and give MCA judges something to argue about.
Too much is just right, and now we know what it feels like. It's the constant nag that traction must always be managed, even at part throttle with sticky new tires on a dry day. It's ferocious wheelspin while casually accelerating in Second gear. It's the realization that if someone pulls alongside in a good bolt-on car, you'd better be sharp; even then, they'll likely beat you to 50 mph. It's knowing that once past 70 mph, nothing can dream of keeping you in sight. It's the joy of considering Fourth as your primary acceleration gear. It's eight cylinders producing 1,000 hp. It's a special kind of cool.
Ken Christely chases boost...
Ken Christely chases boost as we oogle the Kenne Bell GT 500 prototype strapped to the KB Dynojet. As usual, KB had its test mule instrumented like a NASA moon shot, with numerous temperature and pressures logged in laptops and SCT flash-tuning hooked up for adjustments. The GT 500 spent several months on this dyno as it was decoded and the Kenne Bell kit developed.
Even more chill is the way this power is made using a laughably small amount of hardware, about $6,000 in social lubricant, and not even a full day of installation. But that's what you get when Ford does it right and the aftermarket is ready to build on that solid foundation.
The foundation, of course, is the '07 Ford Shelby GT 500. It packages Ford's largest passenger-car V-8, 5.4 (331ci), DOHC, Four-Valve with a six-speed manual transmission and a stout 8.8-inch live axle. But what we learned-as we'll detail in a minute-is the GT 500 is blessed with numerous valuable supporting parts, which make hypercharging it a breeze.
Well, it's a breeze if you're Kenne Bell and have already sorted through this process with a massive amount of in-house brainpower. Ford already prepped the GT 500 with all the good parts. Kenne Bell was ready with Twin Screw blower kits for all the modular-engined Mustangs, as well as kits for the similar Ford GT supercar. KB recently stepped up its blower program with larger Twin Screw superchargers ("Home Screwed," Nov. '06, p. 48). The company also has Jim Bell's engineering talent and Ken Christely, the in-house electronic tuner who designed this project.
The project has spawned the expected Kenne Bell blower kits (Stages 1 through 3) for the GT 500. There's also a pile of research about the supercharging stratosphere that's so fun to read about, not to mention pedal down the road.
As the only working GT 500...
As the only working GT 500 kit hardware was on the test mule, we photographed this blower-case mock-up and prototype adapter plate to show how it fits. The important part is the new inlet, the aluminum casting at the rear of the supercharger. KB made sure it flowed as much as the Ford intake manifold-1,700 cfm-so it couldn't be a restriction.
Following a well-established development procedure, KB borrowed a new, completely stock GT 500 from Earl Moorehead of Earl's Automotive. Strapping it to the Dynojet, KB optimized the stock Eaton-supercharged, charge-cooled engine, and then removed the Eaton Roots-style. KB's latest 2.8 big-bore Twin Screw supercharger was bolted on next, and the car began climbing the boost ladder. As expected, the H-version (high internal-pressure ratio) of the 2.8 proved more efficient at around 15 pounds of boost, so that's what was used to take the combination up to an all-out, everything-fresh 24 pounds of boost. And to relieve any suspense, its best-ever number was 810 rwhp at that boost.
Some relief. Now you really want one.
Getting the 2.8H Kenne Bell onto the GT 500 was mechanically simple, although hood clearance was tight. The underhood padding had to be removed, and a small notch in the reinforcing web structure was required. The Twin Screw supercharger was bolted to the stock Ford intake manifold using a thin adapter, and no changes were required in the front engine dress. Kenne Bell incorporated the large bypass into the right rear of the installation. It wasn't the most compact bypass placement, but Ken wanted it in an easily accessible location for no-hassle servicing.
The large holes and elbow...
The large holes and elbow at the right rear of the assembly are part of the bypass system.
Driving the long 2.8 supercharger required a new, more compact front blower pulley and drive to retain the stock drivebelt location. The blower pulley was redesigned to fit over the blower's drive snout, not in front of it as with previous KB superchargers. Kenne Bell developed this drive in 31mm and 77mm versions. The GT 500 fitment uses the 31mm drive.
As rapid blower-pulley changes are an important part of Kenne Bell's blower strategy, the quick-change KB pulley capability was preserved. The only practical change is the new pulley uses four small bolts instead of two larger ones.
Minimum blower-pulley diameter is limited to 2.5 inches by the blower drive. As this delivers 24 pounds of boost, we doubt anyone will mind. Other available pulley diameters are 2.75, 3.00, 3.25, and 3.50 inches. When the higher-boost 2.500 and 2.750-inch pulleys are run, the stock blower belt is used. The 3-inch-and-larger pulleys require a longer blower belt. Ken says this longer belt might be supplied with all Kenne Bell GT 500 kits, although the final details were still being decided at press time.