Modular Motor Shootout - Three is the New Four

Adam and Kenne Bell electronics... 

   

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Adam and Kenne Bell electronics expert Ken Christley may look like two goats staring at a watch here, but don't think they've been sliding by on good looks alone. The pair did a great job demonstrating what the current Mustang GT is capable of.

How did the new Mustang GT fare? After weeks of dynoing, electronic tuning, fabrication, and brain-bleeding head-banging, the GT tire smoke blew away to reveal three meaningful dyno sheets at 16, 18, and 20 pounds of peak boost using the 2.6H supercharger

Why just three? For one, lesser boost levels had already been explored in previous testing and articles. Also, the new, large, 2.6-liter Kenne Bell superchargers are best suited for high-boost applications. The standard 2.6 does fine at lesser boosts, but the 2.6H has the ability to blow where other blowers hadn't blown before. Finally, while many dyno pulls were made during a two-month period, it took a while for the supporting hardware-mass air meters and throttle bodies-to catch up with the 2.6 blower and Three-Valve engine combination potential. In the end, they made all the difference

Not only did the stock Three-Valve's lack of mechanical strength become an issue at high boost, but the throttle body and mass air meter are must-haves for huge power. The standard Kenne Bell S197 kit includes a Cool-Air Kit built from a 9-inch conical air filter, matching large-diameter air ducting, and a 90mm mass air meter from the Lightning truck, but uses the stock twin-bore throttle body. This combination will push you into the seat, as the stock throttle body is good well past 500 rwhp, maybe up to 550 rwhp. For the all-out power Adam was spooling up, the stock throttle body proved the choke in the system.

The bulk of the truck throttle... 

   

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The bulk of the truck throttle body doesn't make it easy to fit up against the KB supercharger. ST Motorsports cobbled this sheet-aluminum adapter together to test the V-10 throttle body on the Three-Valve. Accufab's prototype 2x60mm throttle body made nine more horsepower than the V-10 Ford part, but until Accufab hits the streets, the over-the-counter V-10 Ford unit is a good way to go.

What a choke it was. Adam hit the wall at 550-565 rwhp, and nothing would get the GT past that point until a Ford 2x60mm V-10 throttle body was experimentally fitted. It helped tremendously, but was hopeless in the real world; it was never going to fit the KB kit. The company had longtime collaborator Accufab spool up a 2x60mm throttle body that would work, and it came out nine rwhp ahead of the Ford V-10 part. How much more is that than the stock Mustang GT throttle body when stuffing 18 or so pounds of boost down the Three-Valve's throat? More than 80 rwhp, believe it or not. In this case, Accufab made 652 rwhp with 103-octane unleaded and just under 20 pounds of boost. The best the stock throttle body ever did was 568 rwhp under similar conditions

Because the KB blower allows rapid, four minute pulley changes as long as you have the KB pulley wrench ($25) and the necessary pulleys ($69/each), Adam was able to run the Three-Valve back-to-back with no changes, save for pulley swaps. The results for the 2.6H are as follows.

The Three-Valve is looking fine compared to prior Cobra numbers. In fact, after goofing around with our Casio, it seems the Three-Valve is 35 hp ahead of the Cobra at 17 and 20 pounds of boost. Don't forget the Cobra was huffing through stock cats while the Three-Valve benefited from gutted units, possibly accounting for the increases seen here

Looking at it another way, what Kenne Bell has essentially done, given the Sean Hyland short-block and the fact that the KB blower kit uses the Cobra charge cooler in a KB intake manifold, is essentially build a Cobra Terminator engine around a set of Three-Valve cylinder heads. That's smart, and it happens to be a good way of testing them. What we found is the Three-Valve head runs with the Four-Valve variety. Our comparison has enough variables in it that we can't authoritatively say who wins the battle of the cylinder heads-the Three-Valve numbers were posted with KB's latest-style, larger-displacement blower, and we're not sure how much those gutted cats are worth-but there's no doubt it's a close contest. Savvy racers might find the Three-Valve is more torque-friendly than the Four-Valve, which is something to explore. In any case, the newest Kenne Bell blower is ready to make huge power when your Three-Valve is ready

At higher boost pressures,...        read full caption At higher boost pressures, the supercharger tends to "blow out" the spark. KB's answer is the Boost-A-Spark, which ups the voltage through the ignition system. It is typically enough to carry the day on big-power blower engines, as it was here.

When the 90mm Lightning truck...        read full caption When the 90mm Lightning truck throttle body at left proved restrictive around 675 rwhp, something big was in the offing. That turned out to be a section of 4.5-inch diameter pipe with the stock mass air electronics added to it. It's not ready for show duty, but the big mass air got the Three-Valve more than 700 rwhp.

It always takes some help...        read full caption It always takes some help from your friends, as the rear window of ST Motorsport's GT shows.