Supercharger

Supercharger. A supercharger is an air compressor that increases the pressure or density of air supplied to an internal combustion engine. This gives each intake cycle of the engine more oxygen, letting it burn more fuel and do more work, thus increasing power. The power for the supercharger is supplied mechanically by a belt, gear, shaft, or chain connected to the engine's crankshaft, distinguishing it from a turbocharger which is powered by exhaust gas turbine.

Overview

The primary function of a supercharger is to increase an engine's volumetric efficiency by forcing a greater mass of air into the combustion chambers. This process, known as forced induction, allows for a significant power increase over a naturally aspirated engine of the same displacement. Superchargers are used in various applications, from high-performance automobiles and motorcycles to aircraft and marine engines. The concept dates back to the late 19th century, with pioneers like Gottlieb Daimler and Rudolf Diesel exploring early forms of forced induction.

Types of superchargers

There are three main mechanical designs for superchargers, categorized by their method of air compression. The Roots-type supercharger is a positive displacement pump that uses two meshing lobes to move air, often associated with classic American muscle cars like the Ford Mustang and Chevrolet Corvette. The Twin-screw supercharger also uses intermeshing screws but compresses air internally, offering greater efficiency and popularized by companies like Kleemann and Lysholm. The third type is the Centrifugal supercharger, which uses an impeller to accelerate air to high speed, functioning similarly to a turbocharger compressor but driven mechanically; manufacturers such as ProCharger and Vortech specialize in these units.

Operation and components

A typical supercharger system consists of the compressor unit, a drive mechanism, and an intercooler. The drive mechanism, often a serpentine belt connected to the crankshaft pulley, spins the supercharger's internal rotors or impeller at extremely high RPM. As air is drawn in and compressed, its temperature rises significantly, which can lead to engine knocking. To mitigate this, an intercooler, or charge air cooler, is used to lower the intake air temperature before it enters the intake manifold. Additional components may include bypass valves to relieve pressure during light throttle and specialized pulley systems to adjust the level of boost.

Performance and efficiency

Superchargers provide an immediate power increase with minimal turbo lag, as their output is directly proportional to engine speed. This results in strong low-end and mid-range torque, beneficial for applications like drag racing and street performance. However, because they are powered directly by the engine, they impose a mechanical parasitic load, which can reduce overall thermal efficiency compared to turbochargers. The compression process also generates significant heat, necessitating robust engine management strategies, often involving adjustments to the ignition timing and air-fuel ratio by the engine control unit.

Applications

Superchargers have been widely adopted across multiple fields of engineering. In automotive racing, they are iconic in series like NASCAR and the FIA World Rally Championship. Historically, they were critical for World War II aircraft such as the Supermarine Spitfire and North American P-51 Mustang to maintain power at high altitude. In modern production cars, they are featured in models from Mercedes-AMG, Audi, and Jaguar. Beyond vehicles, superchargers are also used in large diesel engines for industrial and locomotive applications.

History and development

The roots of supercharging trace back to the late 19th century, with patents filed by individuals like Dugald Clerk. The first practical use for an internal combustion engine is credited to brothers Philander H. and Francis M. Roots, founders of the Roots Blower Company, in the 1860s, though initially for mine ventilation. Superchargers became prominent in the 1920s and 1930s on grand prix cars from Mercedes-Benz and Auto Union, as engineered by figures like Ferdinand Porsche. Post-war development continued with innovations from companies like General Motors and Eaton Corporation, leading to the widespread adoption of superchargers in both performance and mainstream automotive sectors.