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43-752: SAAB introduced it on the turbo charged Saab H engines in 1982, and the APC was fitted to all subsequent 900 Turbos through 1993 (and 1994 convertibles), as well as 9000 Turbos through 1989. The APC was sold to Maserati to equip the carbureted Maserati Biturbo , with different settings for the Biturbo, and was known as the Maserati Automatic Boost Controller (MABC). The APC allowed a higher compression ratio (initially, 8.5:1 as opposed to 7.2:1, and, on 16-valve variants introduced in 1985, 9.0:1). This improved fuel economy and allowed

86-400: A common shaft. The first prototype was finished in 1915 with the aim of overcoming the power loss experienced by aircraft engines due to the decreased density of air at high altitudes. However, the prototype was not reliable and did not reach production. Another early patent for turbochargers was applied for in 1916 by French steam turbine inventor Auguste Rateau , for their intended use on

129-407: A condition known as diesel engine runaway . Forced induction In an internal combustion engine , forced induction is where turbocharging or supercharging is used to increase the density of the intake air. Engines without forced induction are classified as naturally aspirated . Forced induction is often used to increase the power output of an engine. This is achieved by compressing

172-425: A design by Scottish engineer Dugald Clerk . Then in 1885, Gottlieb Daimler patented the technique of using a gear-driven pump to force air into an internal combustion engine. The 1905 patent by Alfred Büchi , a Swiss engineer working at Sulzer is often considered the birth of the turbocharger. This patent was for a compound radial engine with an exhaust-driven axial flow turbine and compressor mounted on

215-405: A limiting factor in the peak power produced by the engine. Various technologies, as described in the following sections, are often aimed at combining the benefits of both small turbines and large turbines. Large diesel engines often use a single-stage axial inflow turbine instead of a radial turbine. A twin-scroll turbocharger uses two separate exhaust gas inlets, to make use of the pulses in

258-574: A pioneering role with turbocharging engines as witnessed by Sulzer, Saurer and Brown, Boveri & Cie . Automobile manufacturers began research into turbocharged engines during the 1950s, however the problems of "turbo lag" and the bulky size of the turbocharger were not able to be solved at the time. The first turbocharged cars were the short-lived Chevrolet Corvair Monza and the Oldsmobile Jetfire , both introduced in 1962. Greater adoption of turbocharging in passenger cars began in

301-433: A solenoid valve that trims the rate of rise of pressure as well as the maximum pressure by directing boost pressure to the turbocharger's pneumatic wastegate actuator . To detect knock, a piezoelectric knock sensor (basically a microphone ) bolted to the engine block responds to unique frequencies caused by engine knock. The sensor generates a small voltage that is sent to the electronic control unit , which processes

344-420: A supercharger - in order to function. A reduced density of intake air is caused by the loss of atmospheric density seen with elevated altitudes. Therefore, an early use of forced induction was in aircraft engines. At 18,000 feet (5,500 m), the air is at half the pressure of sea level, which means that an engine without forced induction would produce less than half the power at this altitude. Forced induction

387-412: Is done with the use of adjustable vanes located inside the turbine housing between the inlet and turbine, which affect flow of gases towards the turbine. Some variable-geometry turbochargers use a rotary electric actuator to open and close the vanes, while others use a pneumatic actuator . If the turbine's aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio

430-474: Is increasing. The companies which manufacture the most turbochargers in Europe and the U.S. are Garrett Motion (formerly Honeywell), BorgWarner and Mitsubishi Turbocharger . Turbocharger failures and resultant high exhaust temperatures are among the causes of car fires. Failure of the seals will cause oil to leak into the cylinders causing blue-gray smoke. In diesel engines, this can cause an overspeed,

473-538: Is that a turbocharger is powered by the kinetic energy of the exhaust gases, whereas a supercharger is mechanically powered (usually by a belt from the engine's crankshaft). However, up until the mid-20th century, a turbocharger was called a "turbosupercharger" and was considered a type of supercharger. Prior to the invention of the turbocharger, forced induction was only possible using mechanically-powered superchargers . Use of superchargers began in 1878, when several supercharged two-stroke gas engines were built using

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516-402: Is that the optimum aspect ratio at low engine speeds is very different from that at high engine speeds. An electrically-assisted turbocharger combines a traditional exhaust-powered turbine with an electric motor, in order to reduce turbo lag. This differs from an electric supercharger , which solely uses an electric motor to power the compressor. The compressor draws in outside air through

559-411: Is that the two nozzles are different sizes: the smaller nozzle is installed at a steeper angle and is used for low-rpm response, while the larger nozzle is less angled and optimised for times when high outputs are required. Variable-geometry turbochargers (also known as variable-nozzle turbochargers ) are used to alter the effective aspect ratio of the turbocharger as operating conditions change. This

602-490: Is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output. By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum. Because of this, variable-geometry turbochargers often have reduced lag, a lower boost threshold, and greater efficiency at higher engine speeds. The benefit of variable-geometry turbochargers

645-441: Is unable to produce significant boost. At low rpm, the exhaust gas flow rate is unable to spin the turbine sufficiently. The boost threshold causes delays in the power delivery at low rpm (since the unboosted engine must accelerate the vehicle to increase the rpm above the boost threshold), while turbo lag causes delay in the power delivery at higher rpm. Some engines use multiple turbochargers, usually to reduce turbo lag, increase

688-484: Is used to artificially increase the density of the intake air, in order to reduce the loss of power at higher altitudes. Systems that use a turbocharger to maintain an engine's sea-level power output are called "turbo-normalized" systems. Generally, a turbo-normalized system attempts to maintain a manifold pressure of 29.5 inHg (100 kPa). The most commonly used forced-induction devices are turbochargers and superchargers. A turbocharger drives its compressor using

731-739: The Boeing B-17 Flying Fortress in 1938, which used turbochargers produced by General Electric. Other early turbocharged airplanes included the Consolidated B-24 Liberator , Lockheed P-38 Lightning , Republic P-47 Thunderbolt and experimental variants of the Focke-Wulf Fw 190 . The first practical application for trucks was realized by Swiss truck manufacturing company Saurer in the 1930s. BXD and BZD engines were manufactured with optional turbocharging from 1931 onwards. The Swiss industry played

774-413: The crankshaft ) whereas a turbocharger is powered by the kinetic energy of the engine's exhaust gas . A turbocharger does not place a direct mechanical load on the engine, although turbochargers place exhaust back pressure on engines, increasing pumping losses. Supercharged engines are common in applications where throttle response is a key concern, and supercharged engines are less likely to heat soak

817-414: The 1980s, as a way to increase the performance of smaller displacement engines. Like other forced induction devices, a compressor in the turbocharger pressurises the intake air before it enters the inlet manifold . In the case of a turbocharger, the compressor is powered by the kinetic energy of the engine's exhaust gases, which is extracted by the turbocharger's turbine . The main components of

860-543: The Renault engines used by French fighter planes. Separately, testing in 1917 by the National Advisory Committee for Aeronautics (NACA) and Sanford Alexander Moss showed that a turbocharger could enable an engine to avoid any power loss (compared with the power produced at sea level) at an altitude of up to 4,250 m (13,944 ft) above sea level. The testing was conducted at Pikes Peak in

903-771: The United States using the Liberty L-12 aircraft engine. The first commercial application of a turbocharger was in June 1924 when the first heavy duty turbocharger, model VT402, was delivered from the Baden works of Brown, Boveri & Cie , under the supervision of Alfred Büchi, to SLM, Swiss Locomotive and Machine Works in Winterthur. This was followed very closely in 1925, when Alfred Büchi successfully installed turbochargers on ten-cylinder diesel engines, increasing

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946-474: The case of high-performance engines. Four-stroke diesel engines are well suited to forced induction, since the lack of fuel in the intake air means that higher compression ratios can be used without a risk of pre-ignition. Therefore, the use of turbochargers on diesel engines is relatively commonplace. Two-stroke diesel engines have a significantly different operating principle to two-strokes petrol engines, and require some form of forced induction - generally

989-474: The combustion chamber. Theoretically, the vapour power cycle analysis of the second law of thermodynamics would suggest that increasing the mean effective pressure within the combustion chamber would also increase the engine's thermal efficiency . However, considerations (such as cooling the combustion chamber, preventing engine knock and limiting NOx exhaust emissions) can mean that forced induction engines are not always more fuel efficient, particularly in

1032-449: The compressor blades. Ported shroud designs can have greater resistance to compressor surge and can improve the efficiency of the compressor wheel. The center hub rotating assembly (CHRA) houses the shaft that connects the turbine to the compressor. A lighter shaft can help reduce turbo lag. The CHRA also contains a bearing to allow this shaft to rotate at high speeds with minimal friction. Some CHRAs are water-cooled and have pipes for

1075-403: The engine rpm is within the turbocharger's operating range – that occurs between pressing the throttle and the turbocharger spooling up to provide boost pressure. This delay is due to the increasing exhaust gas flow (after the throttle is suddenly opened) taking time to spin up the turbine to speeds where boost is produced. The effect of turbo lag is reduced throttle response , in

1118-416: The engine's basic ignition timing. Turbo charger In an internal combustion engine , a turbocharger (also known as a turbo or a turbosupercharger ) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into the engine in order to produce more power for a given displacement . The current categorisation

1161-559: The engine's coolant to flow through. One reason for water cooling is to protect the turbocharger's lubricating oil from overheating. The simplest type of turbocharger is the free floating turbocharger. This system would be able to achieve maximum boost at maximum engine revs and full throttle, however additional components are needed to produce an engine that is driveable in a range of load and rpm conditions. Additional components that are commonly used in conjunction with turbochargers are: Turbo lag refers to delay – when

1204-418: The engine's intake system, pressurises it, then feeds it into the combustion chambers (via the inlet manifold ). The compressor section of the turbocharger consists of an impeller, a diffuser, and a volute housing. The operating characteristics of a compressor are described by the compressor map . Some turbochargers use a "ported shroud", whereby a ring of holes or circular grooves allows air to bleed around

1247-410: The flow of exhaust gases to mechanical energy of a rotating shaft (which is used to power the compressor section). The turbine housings direct the gas flow through the turbine section, and the turbine itself can spin at speeds of up to 250,000 rpm. Some turbocharger designs are available with multiple turbine housing options, allowing a housing to be selected to best suit the engine's characteristics and

1290-400: The flow of the exhaust gasses from each cylinder. In a standard (single-scroll) turbocharger, the exhaust gas from all cylinders is combined and enters the turbocharger via a single intake, which causes the gas pulses from each cylinder to interfere with each other. For a twin-scroll turbocharger, the cylinders are split into two groups in order to maximize the pulses. The exhaust manifold keeps

1333-404: The form of a delay in the power delivery. Superchargers do not suffer from turbo lag because the compressor mechanism is driven directly by the engine. Methods to reduce turbo lag include: A similar phenomenon that is often mistaken for turbo lag is the boost threshold . This is where the engine speed (rpm) is currently below the operating range of the turbocharger system, therefore the engine

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1376-410: The gases from these two groups of cylinders separated, then they travel through two separate spiral chambers ("scrolls") before entering the turbine housing via two separate nozzles. The scavenging effect of these gas pulses recovers more energy from the exhaust gases, minimizes parasitic back losses and improves responsiveness at low engine speeds. Another common feature of twin-scroll turbochargers

1419-432: The in-dash boost needle "twitches" slightly. The APC unit has a 'knock' output where an LED may be connected. This LED will then light up if knock is detected. Because the knock sensor becomes less accurate at high revolutions, the APC tapers maximum boost pressure after approximately 4,500 RPM. Saab Full Pressure Turbo ( FPT ) models with this unit include the APC name displayed on a non-numeric boost pressure gauge in

1462-411: The instrument panel. Although knock sensors are common even on non-turbocharged and turbocharged engines today, Saab has continued to use the APC name prominently as a differentiating feature. The white area on the left side of the scale shows manifold vacuum under normal driving conditions, the short white dash is atmospheric pressure (engine off), the orange scale is where there is safe turbo boost ,

1505-427: The intake air, to increase the mass of the air-fuel mixture present within the combustion chamber . A naturally aspirated engine is limited to a maximum intake air pressure equal to its surrounding atmosphere ; however a forced induction engine produces "boost", whereby the air pressure is higher than the surrounding atmosphere. Since the density of air increases with pressure, this allows a greater mass of air to enter

1548-502: The intake air. A combination of an exhaust-driven turbocharger and an engine-driven supercharger can mitigate the weaknesses of both. This technique is called twincharging . Turbochargers have been used in the following applications: In 2017, 27% of vehicles sold in the US were turbocharged. In Europe 67% of all vehicles were turbocharged in 2014. Historically, more than 90% of turbochargers were diesel, however, adoption in petrol engines

1591-407: The performance requirements. A turbocharger's performance is closely tied to its size, and the relative sizes of the turbine wheel and the compressor wheel. Large turbines typically require higher exhaust gas flow rates, therefore increasing turbo lag and increasing the boost threshold. Small turbines can produce boost quickly and at lower flow rates, since it has lower rotational inertia, but can be

1634-560: The power output from 1,300 to 1,860 kilowatts (1,750 to 2,500 hp). This engine was used by the German Ministry of Transport for two large passenger ships called the Preussen and Hansestadt Danzig . The design was licensed to several manufacturers and turbochargers began to be used in marine, railcar and large stationary applications. Turbochargers were used on several aircraft engines during World War II, beginning with

1677-399: The range of rpm where boost is produced, or simplify the layout of the intake/exhaust system. The most common arrangement is twin turbochargers, however triple-turbo or quad-turbo arrangements have been occasionally used in production cars. The key difference between a turbocharger and a supercharger is that a supercharger is mechanically driven by the engine (often through a belt connected to

1720-472: The red scale is boost above 0.5 - 0.7 bar where the wastegate may be opened or a fuel cut due to overboost may occur. Saab integrated the APC's boost control functionality with ignition control in 1990 with the introduction of the DI /APC system, available in 9000 models only. The DI/APC system managed knock not only by decreasing boost via a solenoid but by retarding ignition timing as well; DI/APC also managed

1763-409: The signal to determine if, in fact, knock is occurring. If it is, then the control unit activates a solenoid valve that directs boost pressure to the turbocharger's pneumatically controlled wastegate, that opens to bypass exhaust gases from the turbocharger directly to the exhaust pipe, lowering turbo boost pressure until the knock subsides. Knock events that are managed by the APC can be discerned when

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1806-407: The turbocharger are: The turbine section (also called the "hot side" or "exhaust side" of the turbo) is where the rotational force is produced, in order to power the compressor (via a rotating shaft through the center of a turbo). After the exhaust has spun the turbine it continues into the exhaust piping and out of the vehicle. The turbine uses a series of blades to convert kinetic energy from

1849-408: The use of low-octane petrol without causing engine damage caused by knock . The APC controls boost pressure and the overall performance, specifically the rate of rise and maximum boost level - and it detects and manages harmful knock events. To control the turbocharger, the APC monitors the engine's RPM and inlet manifold pressure via a pressure transducer , and uses these inputs to control

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