Brief History
Daimler was the first to patent a forced-induction system for internal combustion engines in 1900. The first supercharger was based on a twin-rotor air-pump design, first patented by American Francis Roots in 1860 (Roots supercharger). The first supercharged production vehicles being built by Mercedes and Bentley in the 1920s. More and more manufacturers are adding supercharged cars to their line up and as modern engines become well built, many aftermarket products are becoming available.
Supercharger Basics
Superchargers (also known as a blower) help your engine produce more power by forcing and compressing more air (oxygen) into it, therefore you can burn more fuel. More air combined with more fuel, gives a bigger explosion and therefore more power. The supercharger compressor is driven directly by the engine, either using a belt, with a gear and shaft or by a chain drive from the engines crankshaft. Gearing allows the supercharger to spin at over 50,000 rpm’s and produce increased boost.
There are basically two different types of supercharger, positive displacement and dynamic compressors. Positive displacement superchargers deliver a constant amount of boost and dynamic compressor superchargers deliver an increasing amount of boost when the engine speeds up. It’s a little bit more complicated than that, but we won’t worry about it (unless you want to be bored).
Setting up
Setting up an engine with a supercharger has to be done correctly. The correct ratios of air and fuel have to be adhered to, which is around 14 parts air to one part fuel.
The engines general setup may need to be looked at (just the same as on a turbocharged car), such as its ignition system, compression ratio, fuel system etc. Setting up on a modern fuel injected car will benefit from having the cars computer remapped (see engine management), as it is very likely that the amount of air will be outside its program range causing poor running or worse. Most modern engines can generally cope with a mild installation, but just beware.
Compressed air is hot, adding a good (intercooler), can help to reduce the temperature of the air, making the air denser for a better combustion.
It is important to point out that if the compressed air is too hot, if there’s too much boost, a poor mixture, low octane fuel used, or too much ignition advance, this is likely to cause detonation (knocking/pinking). Detonation is where a second explosion of the fuel/air mixture occurs, causing a shockwave effect in the cylinder, this can basically destroy the engine. But most installers will obviously be aware of this and there are many ways to combat this effect. We recommend using higher octane fuel for a start.
There is no cool down time with a supercharger, as it is not lubricated by oil. They normally have sealed pre lubed bearings. However it is important to ensure the engine and supercharger is fully warmed up before gunning it.
Types of Superchargers
Centrifugal Supercharger
The centrifugal supercharger turns an impeller at very high speeds which draws air into a small compressor housing. The air is drawn in at the central part of the impeller, the centrifugal force then pushes the air outwards. There are vanes that surround the impeller which converts the high-speed, low-pressure air to low-speed, high-pressure air. Centrifugal Superchargers are quite efficient. They are small, lightweight and are attached to the front of the engine, being a much neater install. They also make a distinctive whine as they spin up.
Example of a typical Centrifugal Supercharger kit
Example of an installed Centrifugal Supercharger on a FWD car
Roots Supercharger
The Roots Supercharger is the oldest design. When the meshing lobes spin, the air is trapped and forced between the fill side and discharge side. The air is then literally blown (‘blower’) into the intake manifold. You may have seen muscle cars and alike with a roots supercharger, as they are usually large and sit on top of the engine sticking out of the bonnet
Example of a Roots Supercharger kit
Familiar view of a Roots Supercharger on a Carbureted V8
Corsa 1.8 Roots Supercharger – 184 hp
V8 Maverick Roots Blower 6.71
Twin-Screw Supercharger
Looking similar to some Roots type superchargers the Twin-screw Supercharger sucks air in with two meshing lobes, again air is trapped in air pockets. Due to the conical taper shape of the rotors the air is compressed as it moves down towards the discharge side. These Superchargers are therefore more efficient, but cost more to engineer. They also make a noticeable whine/whistle.
Example of a Twin-Screw Supercharger
Example of an installed Twin-Screw Supercharger
BMW M3 Twin Screw Supercharged
Some examples of supercharged cars available straight from the manufacturer
There are two reasons that many car manufacturers fit superchargers to their cars. One, quite simply to produce a performance car, the other to give a smaller engined car a good combination of performance and economy (the later being of a much more mild installation).
- Mini Cooper S
- Jaguar/Daimler (numerous XKR, XJR)
- Mercedes Kompressor (numerous)
- VW Corrado G60
- VW Polo G40
- VW (new engines called ‘superturbo’) a combination of supercharger and turbo
- Ford pickup trucks (numerous – most popular is F150)
- Aston Martins (numerous – DB7, Vantage etc)
- Koenigsegg CCS (Twin Superchargers)
- Lotus Exige S
- Lotus 2-Eleven
- Toyota Corolla Compressor
Bad ass Mustang Cobra with Kenne Bell Supercharger
Advantages/Disadvantages of a Supercharger
Advantages of a Supercharger
- Increased power
- No lag – Consistent power delivery
- Generally better throttle response
- Roots & Twin Screw Superchargers are efficient at low RPM
- Centrifugal Superchargers are more efficient at higher RPM
- Easier to install than turbochargers
- No cool down period
- Added weight to power increase is very good
Disadvantages of a Supercharger
- Consumes a lot of power from the engine (therefore not very efficient)
- Increases the strain on the engine
- Increases the strain on the running gear
