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
by up to 46% more power and 30% more torque.
It was first invented by Gottlieb Daimler (of Daimler Benz
fame) in 1885 and 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 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 30s. AMG, the Mercedes McLaren SLR, Koeniggsegg, the Ford GT and Sprintex
use this type of supercharger.
MG in the 30s 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.