Mark Houlahan
Brand Manager, Mustang Monthly
January 10, 2008

Leave it to gearheads to take an industrial product and utilize it to make more power in an automotive environment. It's happened more times than we can count, but one of the most famous applications is the Roots-style blower. Originally designed for moving air in blast furnaces in the late 1800s, the Roots-style blower was used for decades as an air movement tool for large factories. Even some civil defense air sirens used the Roots-style blower to move air to the horn. Later, the Roots-style blower was used on two-stroke diesels. Since there's no intake stroke to these engines, something was needed to force air into the engine. It wasn't uncommon to see a two-stroke diesel with a Roots-style blower for intake air and a turbo for a power increase.

The most recognizable Roots-style blower in the automotive performance world is the GM and the derivatives of it-the popular 6-71 and 8-71 have been used in hot rodding, drag racing, and diesels for decades. These Roots-style blowers were made famous for sticking out of hoods in the Pro Street days of the '70s. Later, the Roots-style blower saw more factory use in GM cars powered by the supercharged 3800 V-6 (Bonneville SSEI, for example) and their more recent Ecotec four-cylinder. Ford has used the Roots-style supercharger for years, first in the '89 Thunderbird Super Coupe, and more successfully in the '03/'04 Mustang SVT Cobra "Terminator." And let's not forget that the highly popular and baddest high-performance truck-the Gen 2 Lightning-featured a Roots -style blower. Now Roots-style blowers have come full circle with aftermarket kits available for popular applications such as the Mustang and F-150.

The complete intercooled RoushCharger kit is shown here, sans a few bolts and clamps. All you'll need for installation is a well-stocked toolbox, a 50/50 mix of coolant for the intercooler system, and a nice weekend with a friend or two.

But why a Roots-style blower when all your drag racing buddies swear by their centrifugal units? That's simple; it's all in the application. Racers use centrifugals (also originally designed for simple air movement) because they make their boost at high rpm, where a drag racer's always at in the power band. The Roots design is a positive displacement blower; meaning it moves a lot of air at low rpm. That low rpm operating range is perfect for street use and is very desirable for towing applications (which, again, is why the Roots was so popular with the diesel trucks). Peak torque is made at a very low rpm, almost off idle in some applications-perfect for pulling that trailer with your race car or show vehicle on it. The torque curve is also long and flat, which aids acceleration when you have a trailer hanging off the back bumper.

Merv Rego, who owns a restoration and custom shop, along with his wife, Pat, traded up from a 460-powered dualie to the '04 F-150 Lariat seen on the previous page. Not only was the new generation F-series a huge leap from Merv's old dualie in interior luxury, fit, finish, and fuel economy, but the 5.4 Three-Valve power plant was a whole new experience after owning a big-block and pushrods for over 10 years. After towing a few customers' cars with their open-deck steel trailer, the one flaw in the F-series stuck out like a red-head in Harlem. "This thing needs a blower for towing," Merv tells us. A call to Roush Performance for their newest F-series offering, its intercooled RoushCharger, certainly fixed Merv's towing issues, and will for you too. While Roush Performance recommends professional installation, especially for warranty continuation, we wanted to see just what was involved with the installation and opted to tackle it ourselves. So follow along as we hit the highlights of the installation and decide for yourself.

On The Dyno
This '04 F-150 has a scant 14,000 miles on it, since the owner uses it primarily for work-and-play towing and not as a daily driver. We brought the Lariat to Source Interlink Media's Florida tech center, where it was strapped down to our in-house Mustang Dyno for before-and-after power numbers. Peak numbers show 313 hp at 5,000 rpm and 371 lb-ft of torque coming in at 4,{{{200}}} rpm. That's an improvement of 111 hp and 120 lb-ft of torque at the max numbers. If you look under that curve, we have a full 130 lb-ft of torque increase at just 3,200 rpm, right where you need it for towing. Shortly after the installation (and we mean like two days later!) Merv towed his project Mustang to a big show in Augusta, Georgia. A round trip of over {{{900}}} miles may not have been the best proving ground to make sure there were no problems, but he reported excellent towing power and even decent gas mileage upon his safe return.
Base 5.4 3-ValveRoushCharged 5.4 3-Valve
RPMTorqueHPRPMTorqueHP
1,{{{600}}}85261,60018865
1,800107371,80019576
2,000128492,00020487
2,200155652,20020897
2,4002591202,400210105
2,600199992,600228119
2,8001981062,800261143
3,0002111213,000271154
3,2002111293,200334198
3,4002141393,400344224
3,600237{{{164}}}3,800332242
3,8002511824,000341261
4,0002471894,200371297
4,2002421944,400340286
4,400{{{240}}}2024,600334294
   4,800331304
   5,000327313

The Goods

  • Roush Performance RoushCharger with Intercooler, PN R07000012
  • Application: '04-'06 F-150 and Mark LT, 2WD and 4WD 5.4 3V Engine
  • Suggested Retail: $5,975
  • Requires 91-octane or better fuel