This technical topic is about the supercharger designed for maximum power from an internal combustion engine, not the “superchargers” that Elon Musk is building to provide fast charging for his Tesla cars.
Like many technologies that are in use today, supercharging an internal combustion engine has been around for over 100 years! The concept is quite simple: take an engine where air and fuel is mixed before combustion, then force more air/fuel mix into the cylinder thus creating a bigger bang and more force for the piston creating more power through to the crank. A normally aspirated engine can only suck in the volume of the cylinder, however forcing in more using a supercharger or turbo means a bigger explosion because you add in more fuel! The theory is that for an optimal ignition you need 14 parts air to one part fuel. The only way to achieve greater power is to use more fuel, hence the need for more air!
Supercharging uses an air compressor attached to the engines crankshaft to pressurise air thus increasing its volume and increases an engine’s output by up to 46% more power and 30% more torque. It was first invented by Gottlieb Daimler (of Daimler Benz fame) in 1885 and he patented his design. Louis Renault developed the centrifugal supercharger in 1902.
There are two types of compression: positive displacement and dynamic. “Positive displacement” provides the engine with a constant boost and “dynamic” compression increases boost with the increase in engine speed although full boost is only reached when the engine is near the peak rpm. Renault’s centrifugal model is an example of a dynamic compression supercharger. Today Vortech use the centrifugal model for their products.
The most well known positive displacement supercharger is the Roots type named after the inventors of an air pump in 1860, Philander and Francis Roots. It is their theory and method of pumping air using intertwining lobes that Daimler used in his first supercharger. The Roots type is the least fuel efficient of all superchargers; although Eaton who use a Roots type model for their superchargers has developed the technology further to address the consumption issue.
Another type of positive displacement supercharger is the Lysholm Screw. This uses intertwining screws and is based on a patent from 1878 by Heinrich Krigar, a German who developed the concept of screw compression. Alf Lysholm was a Swede who extended Krigar’s concept and patented his design in the 1930s. AMG, the Mercedes McLaren SLR, Koeniggsegg, the Ford GT and Sprintex use this type of supercharger.
MG in the 1930s used a sliding vane type supercharger that was similar to the Roots type but used thinner vanes instead of cast lobes. Manufacturing was easier but the whole design was more expensive to assemble.
Like the sliding vane, the scroll supercharger used thin plates to compress the air. Invented in 1905 by Frenchman Leon Creux, it was further developed by Volkswagen as the G-Lader. This explains why their supercharged models are called the G40 or G60 – based on the size of the scroll in mms.
Interestingly, the sliding vane and scroll superchargers work in a similar way to the Wankel rotary engine, a type of motor that only Mazda is using in car production.