Turbocharger

Who invented the turbocharger?

Before the turbocharger existed, forced induction was achieved exclusively by mechanically driven superchargers. Scottish engineer Dugald Clerk built the first supercharged two-stroke gas engines to his own design in 1878, and in 1885 Gottlieb Daimler patented the use of a gear-driven pump to force air into an internal combustion engine.

The 1905 patent filed by Alfred Büchi, a Swiss engineer employed at Sulzer, is widely regarded as the birth of the turbocharger. His patent described a compound radial engine in which an exhaust-driven axial-flow turbine and a compressor were mounted on a single common shaft. French steam turbine inventor Auguste Rateau filed a separate turbocharger patent in 1916, specifically for use on Renault engines powering French fighter aircraft.

Early development and aviation applications

Büchi's first prototype was completed in 1915, with the goal of counteracting the power loss that aircraft engines suffered at high altitudes due to reduced air density. The prototype proved unreliable and did not enter production.

Independent testing carried out in 1917 by the National Advisory Committee for Aeronautics (NACA) and Sanford Alexander Moss, using the Liberty L-12 aircraft engine at Pikes Peak in the United States, demonstrated that a turbocharger could allow an engine to maintain its sea-level power output at altitudes of up to 4,250 metres (13,944 ft). During the Second World War, turbochargers were fitted to several American aircraft, beginning with the Boeing B-17 Flying Fortress in 1938, whose units were manufactured by General Electric. The Consolidated B-24 Liberator, Lockheed P-38 Lightning, Republic P-47 Thunderbolt, and experimental versions of the Focke-Wulf Fw 190 were among other aircraft to adopt the technology.

First commercial and industrial use

The first commercial turbocharger was the model VT402, delivered in June 1924 from the Baden works of Brown, Boveri & Cie — under Alfred Büchi's supervision — to SLM, the Swiss Locomotive and Machine Works in Winterthur. The following year, in 1925, Büchi successfully applied turbochargers to ten-cylinder diesel engines, raising their power output from 1,300 to 1,860 kilowatts (1,750 to 2,500 hp). The German Ministry of Transport employed these engines in two large passenger ships, the Preussen and the Hansestadt Danzig.

Swiss truck manufacturer Saurer brought the technology to road freight during the 1930s, producing its BXD and BZD engines with optional turbocharging from 1931 onward. Switzerland's role in pioneering turbocharging during this period was substantial, with Sulzer, Saurer, and Brown, Boveri & Cie all contributing to its development. Büchi's engine design was licensed to several manufacturers, and turbochargers were progressively adopted for marine, rail-car, and large stationary power applications.

When did turbocharged cars reach production?

Automobile manufacturers began researching turbocharged engines during the 1950s, but two obstacles blocked early progress: turbo lag — the delay in power delivery caused by the time required for the turbocharger to reach its peak rotational speed — and the considerable physical size of the units available at the time. Neither problem was resolved satisfactorily in that decade.

The first turbocharged production cars appeared in 1962: the Chevrolet Corvair Monza and the Oldsmobile Jetfire. Both were short-lived. Turbodiesel passenger cars entered the global market in the 1970s, with the Mercedes 300 D representing a significant milestone. Broader adoption of turbocharging in petrol-engined passenger cars followed in the 1980s, primarily as a means of extracting greater performance from smaller-displacement engines.

Turbochargers in motorsport

The turbocharger found early competitive success in circuit racing. The 1968 Indianapolis 500 was the first large-scale race recorded as won by a turbocharged engine, and turbocharged cars continued to dominate that circuit in subsequent years. Porsche was an early adopter in production-based motorsport: the air-cooled flat-six engine derived from the 1963 Porsche 911 was turbocharged in 1973, and in 1976 the Porsche 935 and Porsche 936 won both categories of the Sportscar World Championship as well as the 24 Hours of Le Mans, demonstrating the reliability of turbocharged competition machinery.

Formula One turbocharger victories began in the late 1970s, where the technology proved especially effective at generating high power outputs from small-displacement engines. The first Formula One Constructors' and Drivers' World Championship won using a turbocharged engine came in 1983, powered by an engine derived from the BMW M10 four-cylinder block, a design that itself dated back to 1961.

How does a turbocharger work?

A turbocharger consists of three principal assemblies: a turbine, a centrifugal compressor, and the center housing hub rotating assembly that connects and supports them. Exhaust gases leaving the engine pass through the turbine section — sometimes called the hot side or exhaust side — where a series of blades converts the kinetic energy of the gas flow into the rotational mechanical energy of a shaft. This shaft drives the compressor on the opposite end of the unit.

The compressor pressurises the intake air before it reaches the inlet manifold, forcing a greater mass of air into the engine's cylinders than atmospheric pressure alone would supply. The turbine in most automotive applications uses a radial design, while the compressor is typically of the centrifugal type. After the exhaust gases have transferred their energy to the turbine, they continue through the exhaust system and exit the vehicle in the normal way.

Turbocharger vs. supercharger

Both turbochargers and superchargers are forced induction devices that compress intake air to raise engine power, but their energy sources differ fundamentally. A supercharger is driven mechanically, most commonly by a belt connected to the engine's crankshaft, meaning it consumes a portion of the engine's own output. A turbocharger, by contrast, is driven entirely by the energy present in the exhaust gas stream, energy that would otherwise be lost through the exhaust.

The distinction was not always drawn clearly: until the mid-twentieth century, the turbocharger was referred to as the turbosupercharger and was categorised as a subset of the supercharger family. The two device types are now treated as separate technologies.

Frequently asked questions

Sources

1. Wikipedia: Turbocharger — Factual basis of this entry