The origins of the turbocharger lie in early aviation research. Alfred Büchi, a Swiss engineer at Sulzer, filed the foundational patent in 1905 for a compound radial engine with an exhaust-driven axial-flow turbine and compressor on a common shaft. A prototype followed in 1915, aimed at recovering altitude-related power loss in aircraft engines, but it proved unreliable and did not enter production. In 1916, French steam-turbine inventor Auguste Rateau separately patented a design intended for Renault aero-engines used by French fighter aircraft.
In 1917, testing by the National Advisory Committee for Aeronautics (NACA) and engineer Sanford Alexander Moss at Pikes Peak demonstrated that a turbocharger could preserve sea-level power output up to 4,250 m altitude using the Liberty L-12 aero engine. The first commercial application came in June 1924, when Brown, Boveri & Cie delivered the VT402 heavy-duty turbocharger, under Büchi's supervision, to the Swiss Locomotive and Machine Works in Winterthur. A year later, Büchi installed turbochargers on ten-cylinder diesel engines for the German Ministry of Transport, raising power from 1,300 to 1,860 kW (1,750 to 2,500 hp) for two large passenger ships, the Preussen and Hansestadt Danzig.
During the 1930s, Swiss truck manufacturer Saurer became the first to offer turbocharged truck engines commercially, producing the BXD and BZD with optional turbocharging from 1931 onwards. By World War II, turbochargers had been applied to major American aircraft including the Boeing B-17 Flying Fortress (from 1938), the Consolidated B-24 Liberator, the Lockheed P-38 Lightning, and the Republic P-47 Thunderbolt, all using General Electric turbochargers.
The first turbocharged passenger cars were the Chevrolet Corvair Monza and Oldsmobile Jetfire, both introduced in 1962, though neither proved durable and both were short-lived. The 1968 Indianapolis 500 marked the first major race victory with a turbocharged engine. Porsche demonstrated reliability in endurance and sports car racing, with the Porsche 935 and Porsche 936 winning the Sports Car World Championship and the 24 Hours of Le Mans in 1976. Formula One saw its first turbo victories in the late 1970s, and in 1983, Nelson Piquet and the Brabham-BMW claimed the Drivers' and Constructors' championships using a turbocharged four-cylinder engine based on BMW's M10 block, which dated to 1961.
Turbodiesel passenger cars reached the global market in the 1970s with the Mercedes 300 D, and broader adoption in petrol passenger cars accelerated through the 1980s as a means of extracting performance from smaller displacement engines.
The three main assemblies of a turbocharger are the turbine, the compressor, and the centre housing hub rotating assembly (CHRA).
The turbine — the "hot side" — extracts kinetic energy from exhaust gas flow via a series of blades, spinning at up to 250,000 rpm. The turbine housing directs exhaust gas through the turbine, after which the gas continues into the exhaust system. Turbine size is a key trade-off: larger turbines tolerate higher flow rates and peak power but increase lag and raise the boost threshold; smaller turbines respond quickly but limit peak output.
The compressor draws ambient air through the intake, pressurises it, and feeds it into the inlet manifold and combustion chambers. The compressor section comprises an impeller, diffuser, and volute housing. Some turbochargers incorporate a ported shroud — a ring of holes around the compressor blades — to resist surge and widen the efficient operating range.
The CHRA houses the shaft connecting the two wheels and a bearing system that allows rotation at high speed with minimal friction. Many CHRAs are water-cooled to protect lubricating oil from heat degradation.
Twin-scroll turbochargers route exhaust from different cylinder groups into separate spiral chambers before the turbine, preventing pulse interference, recovering scavenging energy, and improving low-speed response. The two nozzles are typically different sizes: a smaller, steeper nozzle for low-rpm boost, and a larger, shallower nozzle for high-output conditions.
Variable-geometry turbochargers use adjustable vanes in the turbine housing to alter the effective aspect ratio as operating conditions change. This keeps the turbine operating at its optimum efficiency across the rpm range, reducing lag and improving response at both low and high engine speeds.
Electrically-assisted turbochargers add an electric motor to the shaft assembly to spin the compressor before exhaust flow is sufficient, further reducing lag in stop-and-go or low-speed conditions — distinct from a standalone electric supercharger, which uses no exhaust-driven turbine at all.
Turbo lag is the delay between a sudden throttle opening and the turbocharger reaching a speed sufficient to produce boost. It arises because exhaust flow must accelerate to spin the turbine up. Methods to reduce turbo lag include using lighter rotating components (including ceramic materials), twin-scroll designs, variable nozzle geometry, sequential or parallel twin-turbo arrangements, antilag systems, and electrically assisted designs.
The boost threshold is a related but distinct phenomenon: at very low engine speeds, exhaust flow is simply insufficient to produce meaningful boost regardless of throttle position. Both effects create perceived power delays and are primary considerations in turbocharger sizing and mapping.
Intercoolers cool the compressed intake air before it enters the engine, increasing air density and reducing the risk of detonation. Wastegates limit maximum boost pressure by diverting exhaust gas away from the turbine above a set threshold. Blowoff valves release compressor pressure when the throttle closes suddenly, preventing compressor stall. Water injection sprays water into the intake charge as an additional cooling measure.
Turbochargers are used in petrol and diesel car engines, truck and bus engines, motorcycle engines, aircraft piston engines, marine engines, locomotives, and stationary industrial applications. By 2017, 27 percent of vehicles sold in the United States were turbocharged. In Europe, 67 percent of all vehicles sold in 2014 were turbocharged. Historically, diesel applications dominated the turbocharger market, but petrol adoption has grown steadily. The leading manufacturers in Europe and the United States are Garrett Motion (formerly Honeywell Turbo Technologies), BorgWarner, and Mitsubishi Turbocharger.