Traditional Roots-style superchargers generally produce on-the-spot boost pressure down low in the rpm band and maintain it as engine speeds increase. However, efficiency generally tapers off at higher rpm due to heat buildup inside the case and leakage past the rotor seals. The added temperature may make the engine more prone to detonation. Two ways to counteract this problem are to run a slightly larger blower, which helps move more air, and underdriving the blower slightly to reduce boost.
Not all Roots-style superchargers operate with the same technology. Some are newer with hybrid designs, such as the Eaton or Magnuson models. These units use a high-helix set of involuted rotors that produce an axial airflow. In other words, they run the air movement from the back of the unit and discharge it at the front. This differs from the traditional Roots supercharger that pulls air in from the top and delivers it through the bottom. A Magnuson-style unit also incorporates a bypass or unloader valve that bleeds off air pressure at part-throttle operation, thus reducing mechanical losses.
The outward appearance of a twin-screw supercharger appears very similar to a traditional Roots-style unit, but there are a few distinct differences. A twin-screw's air compression takes place inside the supercharger, making it an internal-compression unit. Second, a screw-type blower uses rotors with tighter clearances that interleave to pull in and compress the air as it passes through. Third, the incoming air enters the twin-screw supercharger through the rear or top rear. The shorter airflow path of a twin-screw minimizes the high turbulence, friction, heat (reduced often by 50 percent), and pumping losses commonly found with the traditional Roots designs. Like all superchargers, the twin-screw is beltdriven. Because of the closer tolerance design, a twin-screw supercharger is often more expensive than a standard Roots type.
Centrifugal superchargers are installed along the front of the engine in line with other driven accessories (e.g., alternators and A/C compressors). A step-up drive inside the blower increases the speed of the internal impeller. Depending on the size and design, centrifugal blowers are capable of large power increases, while their compactness allows them to fit a variety of engines.
Since a dedicated intake manifold isn't needed, they're easily adaptable to late-model, fuel-injected vehicles. Systems for late-model cars are available from ProCharger and Vortech. These packages typically come with the supercharger, ducting, oil lines, and brackets. Some race units enable big cubic-inch, high-boost applications to make over 1,300 hp.
While the noncentrifugal blower typically builds boost early and maintains it as rpm increases, a centrifugal blower typically builds boost exponentially. This means that as the blower's rotational rpm increases, the boost increases at a quicker rate. Key advantages of the boost increasing at higher engine speed are that there are fewer traction and detonation problems.
Externally, a twin-screw supercharger looks much like the common Roots design, but the dif
The Whipple twin-screw operates on three principles: inlet, compression, and discharge pha
For this particular application, a larger big-block Chevy snout is incorporated onto a spe