Richard Holdener
November 21, 2011

It's been documented that the new Boss is set from the factory for some serious on-track antics. In the right hands, it can run 11s stock and cut corners with some of Europe's best.

Under the hood, the 11.0:1 DOHC 5.0L received CNC-ported four-valve heads, revised cam timing, and a trick new intake manifold. Also part of the package are forged rods and upgraded valvetrain components. The mods push the output to 444 hp at an amazing 7,500 rpm. The new valvesprings allow the Boss motor to rev cleanly to 8,400 rpm (when the factory rev limiter is bypassed). Those changes actually dropped peak torque from 390 lb-ft at 4,250 rpm to 380 lb-ft at a slightly higher 4,500 rpm, but the fun zone in the Boss motor can be found at the top of the rev range.

Examining the word Boss, we discovered that it is very close to a word near and dear to our hearts-namely, boost! But in this case, there were a few concerns, including the static compression and variable cam timing. How would these respond to positive pressure? To find out, we took a Boss to Kenne Bell, one of the leaders in supercharger technology for decades.

(Thanks to Tracy Keller and Maximum Velocity Performance for use of its Boss for this test. Tracy even drove from San Antonio to KB's home is Rancho Cucomunga, California.)

Having previously run testing on the new supercharger kit for the 5.0L Coyote, we decided the Boss needed something special. In this case, special meant the installation of the big 3.6L blower kit just introduced for the Boss 302. Truth be told, the standard 2.8L blower is likely more than enough for most applications, as the 2.8L twin-screw is capable of supporting 1,000 hp. But for some owners, the idea that "more" is available is reason enough to step up.

Capable of supporting over 1,200 hp, the 3.6L features liquid cooling to minimize the temperature differential between the hot (discharge) and cool (inlet) sides of the supercharger. This differential makes life difficult on the rotors, as the growth rate of the rotors is a function of temperature. The hot and cool sides grow at different rates based on temperature, and the result can be changes in tolerances at both ends. Kenne Bell's exclusive (patent pending) liquid cooling minimizes the temperature differential, which in turn improves both power and reliability, especially at elevated boost levels.

Though the 3.6L Twin-Screw blower is the major power producer of the Kenne Bell Boss kit, it is the attention to detail on the remainder of the components that allows the Coyote motor to take full advantage of that glorious boost. Tucked under the blower inside a high-flow intake manifold is an efficient air-to-water intercooler system.

The system also features a dedicated circulation pump, reservoir, and front-mounted heat exchanger. Cooling the charge temperature is important on any boosted application, but critical on a motor sporting 11.0:1 compression.

Having a big blower is all well and good, but not if you restrict the airflow going to it. When it comes to supercharging, less air in means less boost (and less power). Recognizing that positive displacement superchargers are sensitive to inlet restrictions, KB went to great lengths to maximize the airflow of the sub systems positioned in front of the blower.

Knowing that, just one restrictive component can severely limit a perfectly good supercharged motor, Kenne Bell designed the Mammoth intake manifold to maximize airflow. In addition to offering tremendous airflow (upwards of 1,800 cfm), the Mammoth intake is designed to accept either the stock 80mm or the Kenne Bell 168mm throttle body. Testing at 15 psi on the Boss motor demonstrated that the throttle body upgrade alone is worth over 40 hp. Tested at higher boost levels, where the stock throttle body would represent even more of a restriction, the gains would be even more pronounced.

One thing sure to entice Boss owners is the dedicated Boss/Mammoth plaque attached to each system, replete with individual serial number-as if a Boss Mustang wasn't exclusive enough!

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Feeding the Mammoth intake and 168mm throttle body is nothing less than a 4.5-inch air intake and MAF assembly. The stock air filter and MAF system were never designed for the elevated power levels offered by a supercharged Boss motor. The cavernous Kenne Bell air intake is fed by an equally massive air filter. It's important to note that the air intake positions the filter down in front of the inner fender, well behind the front bumper cover-a position that guarantees a constant supply of fresh, ambient, and not heated, underhood air.

With plenty of airflow into and out of the 3.6L blower, the kit also supplies the necessary fuel. The combination of a new MAF assembly and the presence of boost (to say nothing of the 168mm drive-by-wire throttle body) naturally required custom programming. The custom programming was combined with a fuel system upgrade that includes a set of 75-pound injectors and a Kenne Bell 20V Boost-a-Pump. We were impressed that these simple fuel system changes allowed us to more than double the power output of the factory Boss motor!

Since we were looking for big boost from the Boss, we elected to upgrade to the new eight-rib drive system. Belt slippage can become an issue at higher boost and power levels, so KB designed a dedicated eight-rib drive system that features an optional ATI damper. The ATI damper is available in a variety of different sizes to adjust the boost level, but our testing was run with the smallest Kenne Bell-modified 6.6-inch crank pulley (included in the standard eight-rib kit).

Before installation, we ran the Boss motor in normally aspirated trim. As with previous testing, the 444hp Boss pumped out just a hair under 400 rwhp (and 350 lb-ft) on the DynoJet. Torque production exceeded 300 lb-ft from 2,600 rpm to 6,800 rpm, making for a broad and useable power band.

After the installation, the blower was configured with a 4-inch blower pulley and run through the stock throttle body. The remainder of the Boss was all stock, including the stock exhaust manifolds right back to the factory mufflers. Equipped with the 4.0-inch blower pulley, the intercooler 3.6L Kenne Bell produced 15.2 psi of boost. The supercharged Boss pumped out 725 hp and 558 lb-ft of torque. That, my friends, is serious power.

Replacing the stock throttle body with the 168mm unit from Kenne Bell resulted in a jump in peak power to 765 hp. Pulley swaps eventually produced 21 psi of boost, and a peak power output of 854 hp and 643 lb-ft of torque, all from an otherwise stock 5.0L. That, my friends, is screwing your Boss!

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