Forced Induction Part 2: How Superchargers Work

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The word supercharger, usually invokes the image of 60’s & 70’s muscle car with big chrome intake poking out the hood. The rumble of the V8 and whine of the supercharger tearing down the drag strip. These are some iconic images to be sure but superchargers have also found themselves in some more benign modern vehicles. We’re going to look at the different types of superchargers and how they work, as well as some pro’s and con’s.

How do they work?

A supercharger works by pumping more air into the engine. Superchargers are driven by the engine, usually by a belt connected to the crankshaft pulley. This means superchargers use some horsepower to create boost. The amount of boost they provide is fixed based on how fast they are able to spin, but changing the size of the pulley connected to the crankshaft allows the user to lower or raise the amount of boost.

Types of Superchargers

There are three main type of superchargers used in automotive applications; Roots, Twin-Screw type and centrifugal. Each have their own advantages and disadvantages which we will look at below.

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Roots Supercharger on a V8

Roots Superchargers

The Roots supercharger is the oldest supercharger design on the market. This supercharger, often chromed, sticking out from the hood of a muscle car. Unlike the other two types of superchargers, it is more of an air pump than a compressor. As such, it delivers air in pulses rather than a constant stream. The Roots supercharger is composed of two or three meshing lobes. These lobes pump air into the engine from very low rpm’s. Roots supercharger provide positive pressure from the instant the engine cranks over. They also provide maximum boost from the moment the throttle body is fully open regardless of the rpm.

How a Roots Supercharger works (c) HowStuffWorks.com

Pro’s of Roots Superchargers

  • Boost throughout the entire RPM range, right off of idle
  • Highest Potential for Gain
  • Excellent Reliability
  • They look amazing, especially on show cars

Con’s of Roots Superchargers

  • Sometimes Violent Throttle Response.
  • The least efficient supercharger design.
  • Lower boost ratings at higher rpms
  • Higher Than Normal Discharge Temperatures
Whipple Twin-Screw Supercharger on a Hemi Engine

Twin-Screw Type Superchargers

The Twin-screw type supercharger also has meshing lobes like the Roots supercharger but these lobes are machined like worm gears. Unlike the Roots lobes however, the twin-screws have a conical taper. This compresses the air before it enters the intake manifold. Twin-screw superchargers are therefore more efficient than Roots. As bonus for petrolheads they make that addictive whine as the air is compressed.

How a Twin-Screw Supercharger works (c) HowStuffWorks.com

Pro’s of Twin-Screw Superchargers

  • Great Power at Low RPMs (Great for Towing)
  • Factory Fit & Appearance
  • Great Reliability

Con’s of Twin-Screw Superchargers

  • Power curve plateaus; it does not keep climbing with rpms
  • Difficult to make high boost or move air volumes
Aftermarket Vortech Centrifugal Supercharger on a 350Z

Centrifugal Superchargers

Centrifugal superchargers use an impeller to draw in air and compress it in a housing similar in shape to a turbo. They are also the most efficient of all the supercharger designs. Like the twin screw, they also create an appealing whine as they spool up. The small lightweight design of the centrifugal supercharger makes it popular in the aftermarket. Many companies offer a centrifugal supercharger to boost naturally aspirated models.

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How a Centrifugal Supercharger works (c) HowStuffWorks.com

Pro’s of Centrifugal Superchargers

  • Lots of Flexibility for Power Adjustments
  • Lower Discharge Temperatures
  • Great Reliability
  • Easy to install

Con’s of Centrifugal Superchargers

  • Not as much power at low RPMs as Roots or Screw type superchargers

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