Roots Superchargers
Roots, or Eaton-style, superchargers are probably the most recognized blowers in the world. As a Mopar lover, you might not like the fact that modern Roots blowers evolved from the GMC 6-71 blower developed in the 1930s, but you have to love the fact that blown Hemis using this type of supercharger have continuously dominated the top classes in drag racing for many years. There are no GM parts in modern Roots blowers, however, because manufacturers such as Littlefield, Eaton, MagnaCharger, BDS, and Holley/Weiand build completely new Roots blowers and blower kits for almost any application.

The compressor of the Roots blower is a positive displacement pump, containing two rotors spinning inside the blower housing to pump air. Early Roots blowers had either two or three-lobe rotors that were straight cut, but modern designs utilize helical rotors with Teflon seals to form a tight clearance between the rotors and the housing. Either way, the air or air and fuel enter the top of the blower, and the mixture is then pumped outward and down the inside of the rotor case, exiting at the bottom. This style of blower typically sits right on top of the engine which creates higher inlet temperatures than centrifugal superchargers. Roots-style blowers are also more difficult to intercool, though there are air/water intercoolers that sit between the blower and the intake.

The latest Roots blowers with "high-helix" rotors are even more efficient than the original design, and reliable Roots supercharger systems are now available for modern and older Mopars, both carbureted and fuel injected. By design, the roots blower provides instant boost for incredible torque and throttle response, even from an idle. Race units are generally set up for mechanical fuel injection to handle the large volumes of fuel required, and injectors can be mounted on top of the blower in the injector "hat" (helping keep the mixture cooler), in the intake below the blower, or in extreme cases, injectors can be installed in both locations. Roots superchargers are also compatible with electronic fuel injection, and small roots blowers can provide big power increases on otherwise stock late model Mopars. Another common setup for older cars is dual carburetors on top of the blower, though this method generally requires cutting a hole in the hood, allowing the world to see your massive display of power.

Screw-Type Superchargers
Screw-Type superchargers, also known as twin-screw, or Lysholm compressors, are very similar externally to Roots style superchargers. They are both positive displacement pumps, and each house a pair of multi-lobe, helical, meshing rotors. But while the two rotors of the screw-type are contained in a case that usually sits atop the intake, just like the Roots, internally, the units are engineered very differently. First, the rotors in a screw-type compressor spin toward the center, or down where they meet, instead of toward the case, or up where they meet, like a Roots supercharger. Next, the rotors of a screw-type blower having a male and female rotor instead of symmetric rotors like the Roots.

Based on an evolved version of a simple screw-type water pump developed by the Greek inventor Archimedes around 200 B.C., the intermeshing spiral rotors of a modern screw-type supercharger are precisely engineered for maximum efficiency. By design, the screw-type blower both moves air forward along the rotors as a positive displacement pump, and also acts as a vane supercharger, further compressing the air as it moves it. This combination of air compression gives screw-type superchargers higher efficiency ratings, and lower inlet air temps, especially at high boost levels, when compared to Roots blowers.