The centrifugal type supercharger
In general terms, a supercharger, which is also commonly known as a blower, is nothing more than a large air pump that is driven by a belt that runs off the crankshaft of an engine. Superchargers have been used on car engines for more than a century already, with the German car manufacturer, Gottlieb Daimler, being credited as the first person to patent a supercharger system for an internal combustion engine. His design was based on the twin-rotor air pump designed by the Americans, Philander and Francis Roots in 1859 and patented in 1860. The first production vehicles to use superchargers were built by Mercedes and Bentley in the 1920's.
Superchargers have become quite common in the car performance industry in recent years, and are even installed as original equipment on some new high performance cars. They have become popular because of their cost efficiency and reliability, but mainly because of their performance. Indeed, supercharging a car engine results in huge power increases between 50% and 100%, making them great for racing and car customizing. In fact, back in the 1980's, there was probably nothing that shouted 'hot rod' louder than a Chevy V8 with a large Roots supercharger sticking out through the hood. But supercharging has come a long way since the 1980's when superchargers were rather inefficient and struggled to make 3 pounds of boost. Today you can walk into any performance parts shop and order any number of efficient Roots supercharger and centrifugal supercharger kits designed specifically for your engine. And with supercharging technology being so advanced, those superchargers could easily double the horsepower of a stock car engine! That's more horsepower than you would ever need!
When people start thinking about fitting a supercharger there are usually two things that they are concerned about. First, they think that the added boost will put strain on the engine parts and will lead to engine damage; but this is not necessarily true. Engine damage is usually caused by excessive RPM but a supercharged engine will make the same amount of horsepower substantially lower RPMs than a stock engine, making high RPMs less of a necessity. The second concern is that some people think that by increasing the engine's compression, a supercharger will cause detonation in the combustion chamber. However, unlike turbochargers, most superchargers do not cause 'overboost' conditions. Superchargers are also designed to operate a boost pressures will not cause detonation, while most superchargers kits also include an intercooler to further detonation while other supercharger kits include a boost timing retard chip that retards the engine's ignition timing under high boost conditions.
A more pertinent consideration should be what supercharger to use, especially with all the different types of superchargers available these days. Choosing the best supercharger for your particular engine can be a bit of a challenge as no single supercharger can be described as "the best". All superchargers work well, and they all have their strengths and weaknesses. What you need is an idea of what you want from the supercharger and an idea of what to expect from each type of supercharger. Especially as different vehicles and different engines may benefit from one type or another; so it's important that you know what you're looking for.
There are two types of superchargers that are commonly used on an internal combustion car engine:
- Centrifugal superchargers, which are very similar to turbochargers; and
- Positive-displacement superchargers, such as the Roots supercharger and the twin-screw supercharger.
Furthermore, there are two different types of positive-displacement superchargers: the twin-screw supercharger and the Roots supercharger, but both are based on the same design principles but they use different types of lobes. Then there is also the sliding vane supercharger, which is not widely used on car engines and won't be discussed here. Of the three superchargers, the centrifugal supercharger is becoming more popular because of its compactness.
In this section we'll discuss the different types of superchargers, and what to expect from each one of them, as well as intercoolers. But we'll start as always with supercharger basics where we'll discuss how the different types of superchargers work.