Comparing the stock 2x60mm...
Comparing the stock 2x60mm throttle body to a 2x75mm is best done from the backside. Both of these are large throttle bodies, but the twin 75mm is huge. We know the larger one here is a cable-actuated unit. The only electronic 75mm throttle body available at the time was already on the car. In fact, once KB goes into full production, it will move to a 2x77mm unit.
As development continued, the first stock-breathing item to give up was the mass air meter. It ran out of electronic capacity at 525 rwhp, but this was cured by adding a Diablo MAFia mass air extender. Airflow through the stock mass air meter was an issue. The plastic meter flows a lot of air with no problems, but it's molded as part of the restrictive Ford air-filter box. KB decided Ford had a great meter, so they duplicated its housing section separately from the airbox. The stock electronic mass air element was transferred from the stock airbox/air meter to the KB mass air tubing. The MAFia Extender was fitted and that was the end for mass air concerns.
On the prototype shown here, the air filter is a flat oval with a washable, cotton-mesh filter made for Kenne Bell. It has generous airflow capacity and shouldn't change in the production kits. An air dam encircling the filter will be developed to quarantine as much hot underhood air as possible.
If getting air into the supercharging system required work, getting it out was hardly a challenge. The stock cast-iron exhaust manifolds and catalytic converter sections of piping work fine. The prototype GT 500 had a Bassani after-cat section that likely helped, but it wasn't tested separately so we're not sure how much it contributed.
The GT 500 fuel system required little to support the Kenne Bell airflow. Similar to Terminator Cobras, the GT 500 uses dual fuel pumps, but the Terminators use a single fuel-pump control module for both. This module electronically varies voltage to the pumps in response to engine-management commands and is the brains of the returnless fuel system. KB has found the Terminator controller overheats when juiced to the max by a Kenne Bell Boost-A-Pump. The high voltage is too much for the controller's electronics at high outputs; they shut down until cooled.
Looking similar to the entrance...
Looking similar to the entrance to the overflow channel at Hoover Dam, the supercharger inlet is sized for the larger throttle body. It's tough to get a sense of scale in these photos, but in person, there's no doubting it flows at least 1,700 cfm.
The GT 500 uses dual fuel-pump controllers, and they have no trouble handling the voltage that the KB Boost-A-Spark zaps at them. And while many said it wouldn't work, the GT 500 has done great with one BAP over two controllers. It's a good thing, too, as a GT 500 with stock injectors needs 92 psi of fuel pressure at full chat.
More good news in the fuel system is the stock 52-lb/hr injectors. Granted, they're maxed at 800 rwhp, but they do get the 5.4 there and don't need to be changed. Fuel pressure is jacked to the moon via the BAP. From the stock 60 psi, it needs to reach 82 psi at 625 rwhp and 92 psi at 700 rwhp or greater. Alternately, fuel pressure could be left at 82 psi and 60-lb/hr fuel injectors used starting at 700 rwhp.
If Ford did a good job on the GT 500's exhaust and fuel systems, the company did even better on the ignition. Ken doesn't know what hardware Ford upgraded on the GT 500 ignition compared to earlier Mustangs, but he figures it could weld pig iron underwater. The only ignition upgrade required turned out to be a swap from Ford's platinum sparkplugs to conventional NGK TR6s gapped to 0.025-inch. Fortunately, the GT 500's 5.4 employs conventionally shaped sparkplugs, not the Three-Valve Mustang GT's stirrup-style ground electrode sparklers.
The minimal amount of parts needed to reach 800 rwhp is amazing. The stock cast-iron exhaust manifolds; stock catalytic converters; the stock engine, including everything inside and the intake manifold; stock front engine assembly dress (belts and tensioners, among other things); the stock clutch; and the stock fuel system, including pumps, controllers, fuel lines, fuel rails, and injectors, were all in place at 810 rwhp.
Naturally, the larger throttle...
Naturally, the larger throttle body requires a larger rubber hose section to fit over it. KB is patterning its inlet hose after the one on the Ford GT supercar. It passed the Kenne Bell flow test easily and poses no restriction.
Bone stock at 8.5 pounds of boost with its 3-inch blower pulley, the Roots-style- blown GT 500 made 444 hp and 428 lb-ft of torque at the wheels on Kenne Bell's Dynojet. Ken electronically tuned the stock combination, making 481 rwhp/462 lb-ft at 8.7 pounds of boost. KB always tunes the stock application to ensure its hardware-and not the tuning-provides the power gains.The ignition timing is locked at 23 degrees for all testing so the computer can't add or subtract it, which would have a huge impact on power. Such control of variables, along with extensive instrumentation and datalogging of temperatures and pressures, is a hallmark of Kenne Bell testing. It's some of the most thorough, scientific testing we've seen in the aftermarket.
A maximum Eaton-boost combination was also tried using a 2.59-inch aftermarket blower pulley and the stock crank pulley. Thus far, you can't go larger on the lower pulley without fouling the cam sensor. This gave 12.3 pounds of boost and 517 rwhp/518 lb-ft on the KB dyno. That's not bad, but the Eaton is hanging out with nothing left to give at this point. Don't forget: You need a custom tune to duplicate these numbers, especially below 3,000 rpm where Ford's GT 500 tune is grandmotherly muted. Ken confirmed our suspicions that the lame response below 3,000 rpm on a showroom-stock GT 500 is from ultra-conservative tuning.