Stage 1 and 2 Kenne Bell kits...
Stage 1 and 2 Kenne Bell kits retain the stock 2x60mm throttle body, requiring this adapter plate at the blower inlet.
Fitting their 2.8H supercharger, KB started with a 3.00-inch blower pulley and an all-stock air-inlet path-stock air filter, mass air meter, rubber hose inlet, and throttle body. This is a larger supercharger turning more slowly than the ultimate Eaton combination. Boost was 12.6 pounds, just 0.3-pound better than the hot-rodded Eaton, but power was a resounding 606 rwhp. That's an 89-rwhp gain over the Eaton's best; all of it is attributable to the larger Twin Screw's superior efficiency.
As testing continued from the summer through the fall of 2006, we can't detail the hundreds of dyno runs made, but hitting the highlights is instructive. One of our favorites came early. Using the plain Stage 1 KB kit-which is simply the 2.8H blower and stock air filter, inlet, and throttle body, a romping 657 rwhp/625 lb-ft was made using a 2.750-inch pulley and pump gas. What's intriguing is the bang-for-the-buck. The Stage 1 kit is the most affordable at $4,599, pump gas is an attraction, and you can't use much more than 650 hp at the tires on the street anyway. Should more be desired at the track, the 2.500-inch pulley could be fitted for a small bump to 19 pounds of boost and 664 rwhp/677 lb-ft using race gas.
Ford put a huge mass air meter...
Ford put a huge mass air meter on the GT 500, but molded it as part of the air filter box. Kenne Bell duplicates the mass air meter as a separate item to integrate with its inlet system. Electronically, the mass air pegs just above stock power levels; a DiabloSport MAFia mass air extender easily handles the situation and is included in all KB GT 500 kits.
If the mid-600-rwhp level is achievable using the stock inlet, it's still not necessarily the most efficient way to get there. By 12 pounds of boost, the Stage 2 KB kit is the way to go. This adds the KB Cool-Air Kit, which is the big air filter and rubber tubing, as well as the Big Oval mass air meter. The stock 2x60mm throttle body is maintained. The limit with pump gas is the 3.00-inch pulley, yielding 14 pounds of boost and 666 rwhp/596 lb-ft of torque. Using the 3.250-inch pulley, it's also well ahead of the Stage 1 kit at 12 pounds of boost-632 rwhp to the Stage 1's 576 rwhp, a 56 rwhp gain.
When reaching for 700 rwhp, the Stage 2 kit shines. With the 2.750-inch pulley, it blows 18 pounds of boost and 708 rwhp/671 lb-ft. That's on race fuel, but it's a great combination for street/strip duty-666 rwhp on pump gas during the week and 708 rwhp at the track with good gas on Saturday night. Best of all, the Stage 2 kit is only $300 more than Stage 1, and the pulley change is simple.
With the boost turned up with a 2.500-inch pulley, the big air filter, mass air, and other parts of the Stage 2 kit installed, it became clear that the major choke was the stock 2x60mm throttle body. A jury-rigged 2x70mm throttle body was tried and found to be not enough, so KB developed the previously mentioned 2x75mm unit. It's a key to the power kingdom, especially at high boost. Given the smallest 2.500-inch pulley of the Stage 2 kit is good for 20 pounds of boost and 727 rwhp, adding the throttle body makes it a Stage 3 and bumps boost to 23 pounds and power to 800 rwhp/738 lb-ft.
The downside to Stage 3 is the cost. The billet electronic throttle body is $900, making the complete Stage 3 kit $5,799. But 700 rwhp won't be passed without it.
We still can't get over how...
We still can't get over how much power can be made through modern exhaust systems. The GT 500 test mule sported a Bassani after-cat. But as you can see, the stock cast-iron exhaust manifolds and the catalytic converters remain.
All Stages are supplied with an SCT flash tuner with a well-developed, intelligently aggressive tune appropriate to the hardware. For the record, we haven't witnessed all the dyno runs, but Kenne Bell showed us 801 rwhp using the 2.500-inch pulley, so we're convinced the power is there.
Ironically, the most powerful Kenne Bell kit is the easiest to install. Removing the Eaton takes less than a half-hour, Ken says. Then the KB adapter plate is screwed to the intake manifold, the blower to it, and finally the throttle body, mass air, and the other parts-if you opt for them. The Boost-A-Pump attaches to the fuel-pump modules in the trunk and is a simple wiring job. The prototype GT 500 didn't have a mounting for the BAP, but it can be zip-tied to any convenient spot, as it's a small, lightweight box. There's also the removal of the underhood insulation pad and a quick cut of the support structure to attend to. That might burn time if you need to find a whiz wheel for the cutting.
Ken says the install takes less than three hours, but we'll go with his "less than eight hours if you're anything close to being competent." Remember, he said it. Ken also noted the whole installation can be reversed to stock, as there is no drilling, bending, or other butchery, other than the small spot on the bottom of the hood. Even that can be covered by the hood pad.
As for the power, it's transformational. If you're hankering to see what too much feels like, don't say we didn't warn you.