Turbocharger - AbsoluteAstronomy.com

A turbocharger, or turbo (colloquialism), from the Greek "τύρβη" (mixing/spinning) is a centrifugal compressor

Centrifugal compressor

Centrifugal compressors, sometimes termed radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.The idealized compressive dynamic turbo-machine achieves a pressure rise by adding kinetic energy/velocity to a continuous flow of fluid through the rotor or impeller...

Turbine

A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...

that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine (forced induction

Forced induction

Forced induction is the process of compressing air on the intake of an internal combustion engine . A forced induction engine uses a gas compressor to increase the pressure, temperature and density of the air...

), thereby resulting in greater performance (for either, or both, power and efficiency). They are popularly used with internal combustion engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

s (e.g., four-stroke engines like Otto cycle

Otto cycle

An Otto cycle is an idealized thermodynamic cycle which describes the functioning of a typical reciprocating piston engine, the thermodynamic cycle most commonly found in automobile engines....

s and Diesel cycle

Diesel cycle

The Diesel cycle is the thermodynamic cycle which approximates the pressure and volume of the combustion chamber of the Diesel engine, invented by Rudolph Diesel in 1897. It is assumed to have constant pressure during the first part of the "combustion" phase...

s). Turbochargers have also been found useful compounding external combustion engine

External combustion engine

An external combustion engine is a heat engine where an working fluid is heated by combustion in an external source, through the engine wall or a heat exchanger. The fluid then, by expanding and acting on the mechanism of the engine, produces motion and usable work...

s such as automotive fuel cell

Fuel cell

A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...

s.

The term turbocharger is a modern one, derived by shortening the turbosupercharger, which was widely used during the World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

era and earlier. This term refers to the fact that turbochargers are a specific type of supercharger

Supercharger

A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...

, one that is driven by a turbine. The most common form of supercharger at the time, which was often referred to as a "geared supercharger", was mechanically driven by the engine, whereas turbochargers are always driven by a turbine that gets its power from the engine's exhaust stream. Twincharger

Twincharger

Twincharger refers to a compound forced induction system used on some piston-type internal combustion engines. It is a combination of an exhaust-driven turbocharger and an engine-driven supercharger, each mitigating the weaknesses of the other...

s combine a supercharger and turbocharger.

Turbochargers are also employed in certain two-stroke cycle diesel engines, which would normally require a Roots blower for aspiration. In this specific application, mainly Electro-Motive Diesel (EMD) 567

EMD 567

The EMD 567 is a line of diesel engines built by General Motors' Electro-Motive Division. This engine, which succeeded Winton's 201-A, was used in EMD's locomotives from 1938 until its replacement in 1966 by the EMD 645. It has a bore of , a stroke of and a displacement of 567 in³ per cylinder...

, 645

EMD 645

The EMD 645 family of diesel engines was designed and manufactured by the Electro-Motive Division of General Motors. Intended primarily for locomotive, marine and stationary engine use, one 16-cylinder version powered the 33-19 "Titan" prototype haul truck designed by GM's Terex...

, and 710

EMD 710

The EMD 710 is a line of diesel engines built by Electro-Motive Diesel . The 710 series largely replaced the earlier EMD 645 series. The EMD 710 is a large two-stroke diesel engine that has a displacement per cylinder. Since its introduction, EMD has continually upgraded the 710G diesel engine...

Series engines, the turbocharger is initially driven by the engine's crankshaft through a gear train and an overriding clutch, thereby providing aspiration for combustion. After the engine achieves combustion, and after the exhaust gases reach sufficient temperature, the overriding clutch disengages the turbo-compressor from the gear train and the turbo-compressor is thereafter driven exclusively by the turbine, which, in turn, is driven by the exhaust gases. In the EMD application, the turbocharger is utilized for normal aspiration during starting and low power output settings and is utilized for true turbocharging during medium and high power output settings. This is particularly beneficial at high altitudes, as are often encountered on western U.S. railroads. One EMD engine model was fitted with a "locked" turbocharger; it was utilized in normal aspiration mode during starting and all power output settings.

History

Forced induction dates from the late 19th century, when Gottlieb Daimler

Gottlieb Daimler

Gottlieb Daimler was an engineer, industrial designer and industrialist born in Schorndorf , in what is now Germany. He was a pioneer of internal-combustion engines and automobile development...

patented the technique of using a gear-driven pump

Pump

A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...

to force air into an internal combustion engine in 1885. The turbocharger was invented by Swiss

Switzerland

Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

engineer Alfred Büchi, who received a patent in 1905 for using a compressor driven by exhaust gasses to force air into a piston engine. During the First World War French engineer Auguste Rateau fitted turbochargers to Renault engines powering various French fighters with some success. In 1918, General Electric

General Electric

General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...

engineer Sanford Alexander Moss

Sanford Alexander Moss

Sanford Alexander Moss was an aviation engineer, he was the first to use a turbocharger on an aircraft engine.-Biography:...

attached a turbo to a V12

V12 engine

A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....

Liberty aircraft engine. The engine was tested at Pikes Peak

Pikes Peak

Pikes Peak is a mountain in the Front Range of the Rocky Mountains, west of Colorado Springs, Colorado, in El Paso County in the United States of America....

in Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

at 14000 feet (4,267.2 m) to demonstrate that it could eliminate the power loss usually experienced in internal combustion engines as a result of reduced air pressure and density at high altitude. General Electric called the system turbosupercharging.

Turbochargers were first used in production aircraft engines such as the Napier Lion

Napier Lion

The Napier Lion was a 12-cylinder broad arrow configuration aircraft engine built by Napier & Son starting in 1917, and ending in the 1930s. A number of advanced features made it the most powerful engine of its day, and kept it in production long after contemporary designs had stopped production...

ess in the 1920s, although they were less common than engine-driven centrifugal superchargers. Ships and locomotives equipped with turbocharged Diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s began appearing in the 1920s. In the aviation world, turbochargers were most widely used by the United States, who led the world in the technology due to General Electric's early start. During World War II

World War II

, notable examples of US aircraft with turbochargers include the B-17 Flying Fortress, B-24 Liberator

B-24 Liberator

The Consolidated B-24 Liberator was an American heavy bomber, designed by Consolidated Aircraft of San Diego, California. It was known within the company as the Model 32, and a small number of early models were sold under the name LB-30, for Land Bomber...

, P-38 Lightning

P-38 Lightning

The Lockheed P-38 Lightning was a World War II American fighter aircraft built by Lockheed. Developed to a United States Army Air Corps requirement, the P-38 had distinctive twin booms and a single, central nacelle containing the cockpit and armament...

and P-47 Thunderbolt

P-47 Thunderbolt

Republic Aviation's P-47 Thunderbolt, also known as the "Jug", was the largest, heaviest, and most expensive fighter aircraft in history to be powered by a single reciprocating engine. It was heavily armed with eight .50-caliber machine guns, four per wing. When fully loaded, the P-47 weighed up to...

. The technology was also used in experimental fittings by a number of other manufacturers, notably a variety of Focke-Wulf Fw 190

Focke-Wulf Fw 190

The Focke-Wulf Fw 190 Würger was a German Second World War single-seat, single-engine fighter aircraft designed by Kurt Tank in the late 1930s. Powered by a radial engine, the 190 had ample power and was able to lift larger loads than its well-known counterpart, the Messerschmitt Bf 109...

models, but the need for advanced high-temperature metals in the turbine kept them out of widespread use.

Turbocharging versus supercharging

In contrast to turbochargers, superchargers are not powered by exhaust gases but are connected directly or indirectly to an engine. Belts, chains, shafts, and gears are only a few of the ways this is performed. Most automotive superchargers are positive-displacement pump

Pump

s, such as the Roots supercharger. Some superchargers are compressor

Gas compressor

A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...

s such as World War II

World War II

piston aircraft engines, to be specific the Rolls-Royce Merlin

Rolls-Royce Merlin

The Rolls-Royce Merlin is a British liquid-cooled, V-12, piston aero engine, of 27-litre capacity. Rolls-Royce Limited designed and built the engine which was initially known as the PV-12: the PV-12 became known as the Merlin following the company convention of naming its piston aero engines after...

and the Daimler-Benz DB 601

Daimler-Benz DB 601

|-See also:-Bibliography:* Mankau, Heinz and Peter Petrick. Messerschmitt Bf 110, Me 210, Me 410. Raumfahrt, Germany: Aviatic Verlag, 2001. ISBN 3-92550-562-8.* Neil Gregor Daimler-Benz in the Third Reich. Yale University Press, 1998-External links:...

, which utilized single-speed or multi-speed centrifugal superchargers.

A supercharger uses mechanical energy from the engine to drive the supercharger. For example, on the single-stage single-speed supercharged Rolls Royce Merlin engine, the supercharger uses up about 150 horsepower

Horsepower

Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...

(110 kW

kw or KW may refer to:* Kuwait, ISO 3166-1 country code** .kw, the country code top level domain for Kuwait* Kilowatt* Self-ionization of water Kw* Cornish language's ISO 639 code* Kitchener–Waterloo, Ontario, Canada...

). Yet the benefits outweigh the costs: For that 150 hp (110 kW), the engine generates an additional 400 horsepower and delivers 1,000 hp (750 kW) when it would otherwise deliver 750 hp (560 kW), a net gain of 250 hp. This is where the principal disadvantage of a supercharger becomes apparent: The internal hardware of the engine must withstand generating 1150 horsepower.

In comparison, a turbocharger does not place a direct mechanical load on the engine. It is more efficient because it converts the waste heat of the exhaust gas into horsepower used to drive the compressor. In contrast to supercharging, the principal disadvantages of turbocharging are the back-pressuring (exhaust throttling) of the engine and the inefficiencies of the turbine versus direct-drive.

A combination of an exhaust-driven turbocharger and an engine-driven supercharger can mitigate the weaknesses of the other. This technique is called twincharging

Twincharger

. Some Crossley

Crossley

Crossley, based in Manchester, United Kingdom, was a pioneering company in the production of internal combustion engines. Since 1988 it has been part of the Rolls-Royce Power Engineering group.More than 100,000 Crossley oil and gas engines have been built....

two-stroke diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s even used a triple system. As the exhaust was through ports, not valves, it was necessary to use exhaust pulse pressure charging

Exhaust pulse pressure charging

Exhaust pulse pressure charging is a system for supercharging two-stroke diesel engines of the loop-scavenge type. Loop-scavenge engines cannot be pressure-charged in the same way as uniflow engines or four-stroke engines because the inlet and exhaust ports are open at the same time.-Overview:The...

. A Roots blower supplied air for
scavenging

Scavenging (automotive)

In automotive usage, scavenging is the process of pushing exhausted gas-charge out of the cylinder and drawing in a fresh draught of air ready for the next cycle....

and a turbocharger provided increased boost pressure when a high enough speed was reached.

Operating principle

All naturally aspirated Otto and diesel cycle engines rely on the downward stroke of a piston to create a low-pressure area (less than atmospheric pressure) above the piston in order to draw air through the intake system. With the rare exception of tuned-induction systems, most engines cannot inhale their full displacement of atmospheric-density air. The measure of this loss or inefficiency in four-stroke engines is called volumetric efficiency. If the density of the intake air above the piston is equal to atmospheric, then the engine would have 100% volumetric efficiency. However, most engines fail to achieve this level of performance.

This loss of potential power is often compounded by the loss of density seen with elevated altitudes. Thus, a natural use of the turbocharger is with aircraft engine

Aircraft engine

An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...

s. As an aircraft climbs to higher altitudes, the pressure of the surrounding air quickly falls off. At 5,486 m

Metre

The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

(18,000 ft), the air is at half the pressure of sea level, which means that the engine will produce less than half-power at this altitude.

The objective of a turbocharger, just as that of a supercharger

Supercharger

, is to improve an engine's volumetric efficiency

Volumetric efficiency

Volumetric efficiency in internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders. More specifically, volumetric efficiency is a ratio of what quantity of fuel and air actually enters the cylinder during induction to the...

by increasing the intake density. The compressor draws in ambient air and compresses it before it enters into the intake manifold

Inlet manifold

In automotive engineering, an inlet manifold or intake manifold is the part of an engine that supplies the fuel/air mixture to the cylinders...

at increased pressure. This results in a greater mass of air entering the cylinders on each intake stroke. The power needed to spin the centrifugal compressor

Centrifugal compressor

is derived from the high pressure and temperature of the engine's exhaust gases. The turbine converts the engine exhaust's potential pressure energy and kinetic velocity energy into rotational power, which is in turn used to drive the compressor

Centrifugal compressor

.

A turbocharger may also be used to increase fuel efficiency without any attempt to increase power. It does this by recovering waste energy in the exhaust and feeding it back into the engine intake. By using this otherwise wasted energy to increase the mass of air, it becomes easier to ensure that all fuel is burned before being vented at the start of the exhaust stage. The increased temperature from the higher pressure gives a higher Carnot efficiency.

The control of turbochargers is very complex and has changed dramatically over the 100-plus years of its use. A great deal of this complexity stems directly from the control and performance requirements of various engines with which it is used. In general, the turbocharger will accelerate in speed when the turbine generates excess power and decelerate when the turbine generates deficient power. Aircraft, industrial diesels, fuel cells, and motor-sports are examples of the wide range of performance requirements.

Pressure increase / boost

In all turbocharger applications, boost pressure is limited to keep the entire engine system, including the turbo, inside its thermal and mechanical design operating range

Operating temperature

An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...

. Over-boosting an engine frequently causes damage to the engine in a variety of ways including pre-ignition, overheating, and over-stressing the engine's internal hardware.

For example, to avoid engine knocking

Engine knocking

Knocking in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.The...

(aka pre-ignition or detonation) and the related physical damage to the host engine, the intake manifold pressure must not get too high, thus the pressure at the intake manifold of the engine must be controlled by some means. Opening the waste-gate allows the energy for the turbine to bypass it and pass directly to the exhaust pipe. The turbocharger is forced to slow as the turbine is starved of its source of power, the exhaust gas. Slowing the turbine/compressor rotor begets less compressor pressure.

In modern installations, an actuator controlled manually (frequently seen in aircraft) or an actuator controlled by the car's Engine Control Unit, forces the wastegate to open or close as necessary. Again, the reduction in turbine speed results in the slowing of the compressor, and in less air pressure at the intake manifold.

In the automotive engines, boost refers to the intake manifold pressure that exceeds normal atmospheric pressure

Atmospheric pressure

Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...

. This is representative of the extra air pressure that is achieved over what would be achieved without the forced induction. The level of boost may be shown on a pressure gauge, usually in bar, psi or possibly kPa. Anything above normal atmospheric level is considered to be boost. The table below is used to demonstrate the wide range of conditions experienced by automobiles in the western hemisphere. In the simple case, the pressure measurement "atm" is approximately equivalent to the effective volumetric efficiency (decimal fraction) as a result of driving at a different altitude. Clearly, turbocharging can be of practical value.

{| class="wikitable"

|
| Daytona Beach
| Denver
| Death Valley
| Colorado State Highway 5
| La Rinconada, Peru,
|-
|altitude
| 0m / 0 ft
| 1,609m 5,280 ft
| -86m / -282 ft
| 4,347m / 14,264 ft
| 5,100m / 16,732 ft
|-
| atm
| 1.000
| 0.823
| 1.010
| 0.581
| 0.526
|-
| bar
| 1.013
| 0.834
| 1.024
| 0.589
| 0.533
|-
| psia
| 14.696
| 12.100
| 14.846
| 8.543
| 7.731
|-
| kPa
| 101.3
| 83.40
| 102.4
| 58.90
| 53.30
|}

In most aircraft engines the main benefit of turbochargers is to maintain manifold pressure as altitude increases. Since atmospheric pressure reduces as the aircraft climbs, power drops as a function of altitude in normally aspirated engines. Aircraft manifold pressure in western-built aircraft is expressed in inches of mercury (Hg), where 29.92 inches is the standard sea-level pressure. In high-performance aircraft, turbochargers will provide takeoff manifold pressures in the 30- to 42-inch Hg (1- to 1.4-bar) range. This varies according to aircraft and engine types. In contrast, the takeoff manifold pressure of a normally aspirated engine is about 27 in. Hg, even at sea level, due to losses in the induction system (air filter, ducting, throttle body, etc.). As the turbocharged aircraft climbs, however, the pilot (or automated system) can close the wastegate, forcing more exhaust gas through the turbocharger turbine, thereby maintaining manifold pressure during the climb, at least until the critical pressure altitude is reached (when the wastegate is fully closed), after which manifold pressure will fall. With such systems, modern high-performance piston engine aircraft can cruise at altitudes above 20,000 feet, where low air density results in lower drag and higher true airspeeds. This allows flying "above the weather". In manually controlled wastegate systems, the pilot must take care not to overboost the engine, which will cause pre-ignition, leading to engine damage. Further, since most aircraft turbocharger systems do not include an intercooler, the engine is typically operated on the rich side of peak exhaust temperature in order to avoid overheating the turbocharger. In non-high-performance turbocharged aircraft, the turbocharger is solely used to maintain sea-level manifold pressure during the climb (this is called turbo-normalizing).

Turbo lag

All turbocharger applications can be roughly divided into 2 categories, those requiring rapid throttle response and those that do not. This is the rough division between automotive applications and all others (marine, aircraft, commercial automotive, industrial, locomotives). While important to varying degrees, turbo lag is most problematic when rapid changes in engine performance are required.

Turbo lag is the time required to change speed and function effectively in response to a throttle change. For example, this is noticed as a hesitation in throttle response

Throttle response

Throttle response or vehicle responsiveness is a measure of how quickly a vehicle's prime mover, such as an internal combustion engine, can increase its power output in response to a driver's request for acceleration, such as a pedal being pressed...

when accelerating from idle as compared to a naturally aspirated engine. Throttle lag may be noticeable under any driving condition, yet becomes a significant issue under acceleration. This is symptomatic of the time needed for the exhaust system working in concert with the turbine to generate enough extra power to accelerate rapidly. A combination of inertia, friction, and compressor load are the primary contributors to turbo lag. By eliminating the turbine, the directly driven compressor in a supercharger

Supercharger

does not suffer from this problem.

Lag can be reduced in a number of ways:

by lowering the rotational inertia of the turbocharger; for example by using lighter, lower radius parts to allow the spool-up to happen more quickly. Ceramic turbines are of benefit in this regard and or billet compressor wheel.
by changing the aspect ratio
Aspect ratio
The aspect ratio of a shape is the ratio of its longer dimension to its shorter dimension. It may be applied to two characteristic dimensions of a three-dimensional shape, such as the ratio of the longest and shortest axis, or for symmetrical objects that are described by just two measurements,...

of the turbine.
by increasing the upper-deck air pressure (compressor discharge) and improving the wastegate
Wastegate
A wastegate is a valve that diverts exhaust gases away from the turbine wheel in a turbocharged engine system. Diversion of exhaust gases regulates the turbine speed, which in turn regulates the rotating speed of the compressor. The primary function of the wastegate is to regulate the maximum boost...

response; this helps but there are cost increases and reliability disadvantages.
by reducing bearing frictional losses; by using a foil bearing
Foil bearing
Foil bearings, also known as foil-air bearings, are a type of air bearing. A shaft is supported by a compliant, spring-loaded foil journal lining. Once the shaft is spinning quickly enough, the working fluid pushes the foil away from the shaft so that there is no more contact...

rather than a conventional oil bearing. This reduces friction and contributes to faster acceleration of the turbo's rotating assembly.
Variable-nozzle turbochargers (discussed below) greatly reduce lag.
by decreasing the volume of the upper-deck piping.
by using multiple turbos sequentially or in parallel.

Boost threshold

Lag is not to be confused with the boost threshold. The boost threshold of a turbo system describes the lower bound of the region within which the compressor will operate. Below a certain rate of flow at any given pressure multiplier, a given compressor will not produce significant boost. This has the effect of limiting boost at particular rpm regardless of exhaust gas pressure. Newer turbocharger and engine developments have caused boost thresholds to steadily decline.

Electrical boosting ("E-boosting") is a new technology under development; it uses a high-speed electrical motor to drive the turbocharger to speed before exhaust gases are available, e.g., from a stop-light. An alternative to e-boosting is to completely separate the turbine and compressor into a turbine-generator and electric-compressor as in the hybrid turbocharger

Hybrid Turbocharger

A hybrid turbocharger is an electric turbocharger consisting of an ultra high speed turbine-generator and an ultra high speed electric air compressor. The turbine and compressor are high-speed aeromachines, as in a conventional turbocharger. The electrical motors run at speeds in excess of...

. This allows the compressor speed to become independent to that of the turbine. A similar system utilising a hydraulic drive system and overspeed clutch arrangement was fitted in 1981 to accelerate the turbocharger of the MV Canadian Pioneer (Doxford 76J4CR engine).

Turbochargers start producing boost only above a certain exhaust mass flow rate. The boost threshold is determined by the engine displacement, engine rpm, throttle opening, and the size of the turbo. Without adequate exhaust gas flow to spin the turbine blades, the turbo cannot produce the necessary force needed to compress the air going into the engine. The point at full throttle in which the mass flow in the exhaust is strong enough to force air into the engine is known as the boost threshold rpm. Engineers have, in some cases, been able to reduce the boost threshold rpm to idle speed to allow for instant response. Both Lag and Threshold characteristics can be acquired through the use of a compressor map and a mathematical equation.

Key components and installation

The turbocharger has three main components:

A turbine
Turbine
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...

, which is almost always a radial inflow turbine
Radial turbine
A Radial turbine is a turbine in which the flow of the working fluid is radial to the shaft. The difference between axial and radial turbines consists in the way the air flows through the components...
A compressor, which is almost always a centrifugal compressor
Centrifugal compressor
Centrifugal compressors, sometimes termed radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.The idealized compressive dynamic turbo-machine achieves a pressure rise by adding kinetic energy/velocity to a continuous flow of fluid through the rotor or impeller...
The center housing/hub rotating assembly (CHRA).

The first two components are the primary flow path components. Depending upon the exact installation and application, numerous other parts, features and controls may be required.

Compressor

Impeller/diffuser/volute housing

Ported shroud/map width enhancement

The flow range of a turbocharger compressor can also be increased by allowing air to bleed from a ring of holes or a circular groove around the compressor at a point slightly downstream of the compressor inlet (but far nearer to the inlet than to the outlet).

The ported shroud is a performance enhancement that allows the compressor to operate at significantly lower flows. It achieves this by forcing a simulation of impeller stall to occur continuously. Allowing some air to escape at this location inhibits the onset of surge and widens the compressor map

Compressor map

Each compressor in a gas turbine engine has an operating map. Complete maps are either based on compressor rig test results or are predicted by a special computer program...

. While peak efficiencies decrease, areas of high efficiency may notably increase in size. Increases in compressor efficiency result in slightly cooler (more dense) intake air, which improves power. In contrast to compressor exhaust blow off valves, which are electronically controlled, this is a passive structure that is constantly open.

The ability of the compressor to accommodate high mass flows (high boost at low rpm) may also be increased marginally (because near choke conditions the compressor draws air inward through the bleed path). This technology is widely used by turbocharger manufacturers such as Honeywell Turbo Technologies, Cummins Turbo Technologies, and GReddy. When implemented appropriately, it has a reasonable impact on compressor map width while having little effect on the maximum efficiency island.

Charge air cooler
Charge air cooler
A charge air cooler is used to cool engine air after it has passed through a turbocharger, but before it enters the engine. The idea is to return the air to a lower temperature, for the optimum power for the combustion process within the engine.Charge air coolers range in size depending on the...

/Intercooler
Intercooler
An intercooler , or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric cooling, which removes...

For all practical situations, the act of compressing air increases the air's temperature along with pressure. This temperature increase can cause a number of problems when not expected or when installing a turbocharger on an engine not designed for forced induction. Excessive charge air temperature can lead to detonation, which is extremely destructive to engines.

When a turbocharger is installed on an engine, it is common practice to fit the engine with an intercooler

Intercooler

An intercooler , or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric cooling, which removes...

(also known as a charge air cooler

Charge air cooler

A charge air cooler is used to cool engine air after it has passed through a turbocharger, but before it enters the engine. The idea is to return the air to a lower temperature, for the optimum power for the combustion process within the engine.Charge air coolers range in size depending on the...

, or CAC), a type of heat exchanger

Heat exchanger

A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...

that gives up heat energy in the charge to the ambient air. To assure the intercooler's performance, it is common practice to leak test the intercooler during routine service, particularly in trucks where a leaking intercooler can result in a 20% reduction in fuel economy.

Fuel-air mixture ratio

In addition to the use of intercoolers, it is common practice to introduce extra fuel into the charge for the sole purpose of cooling. The amount of extra fuel varies, but typically reduces the air-fuel ratio to between 11 and 13, instead of the stoichiometric 14.7 (in gasoline engines). The extra fuel is not burned, as there is insufficient oxygen to complete the chemical reaction, and instead undergoes a phase change from vapor (liquid) to gas. This reaction absorbs heat (the latent heat of vaporization), and the added mass of the extra fuel reduces the average kinetic energy of the charge and exhaust gas. The gaseous hydrocarbons generated are oxidized

Redox

Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

to carbon dioxide, carbon monoxide, and water in the catalytic converter.

A method of coping with this problem is in one of several ways. The most common one is to add an intercooler

Intercooler

or aftercooler somewhere in the air stream between the compressor outlet of the turbocharger and the engine intake manifold. Intercoolers and aftercoolers are types of heat exchanger

Heat exchanger

s that allow the compressed air to give up some of its heat energy to the ambient air. In the past, some aircraft featured anti-detonant injection

Water injection (engines)

In internal combustion engines, water injection, also known as anti-detonant injection, is spraying water into the cylinder or incoming fuel-air mixture to cool the combustion chambers of the engine, allowing for greater compression ratios and largely eliminating the problem of engine knocking...

for takeoff and climb phases of flight, which performs the function of cooling the fuel/air charge before it reaches the cylinders.

In contrast, modern turbocharged aircraft usually forgo any kind of temperature compensation, because the turbochargers are in general small and the manifold pressures created by the turbocharger are not very high. Thus, the added weight, cost, and complexity of a charge cooling system are considered to be unnecessary penalties. In those cases, the turbocharger is limited by the temperature at the compressor outlet, and the turbocharger and its controls are designed to prevent a large enough temperature rise to cause detonation. Even so, in many cases the engines are designed to run rich in order to use the evaporating fuel for charge cooling.

Turbine

The housings fitted around the compressor impeller and turbine collect and direct the gas flow through the wheels as they spin. The size and shape can dictate some performance characteristics of the overall turbocharger. Often the same basic turbocharger assembly will be available from the manufacturer with multiple housing choices for the turbine and sometimes the compressor cover as well. This allows the designer of the engine system to tailor the compromises between performance, response, and efficiency to application or preference. Twin-scroll designs have two valve-operated exhaust gas inlets, a smaller sharper angled one for quick response and a larger less angled one for peak performance.

The turbine and impeller wheel sizes also dictate the amount of air or exhaust that can be flowed through the system, and the relative efficiency at which they operate. In general, the larger the turbine wheel and compressor wheel the larger the flow capacity. Measurements and shapes can vary, as well as curvature and number of blades on the wheels. Variable geometry turbocharger

Variable geometry turbocharger

Variable-geometry turbochargers are a family of turbochargers, usually designed to allow the effective aspect ratio of the turbo to be altered as conditions change. This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds...

s are further developments of these ideas.

The center hub rotating assembly (CHRA) houses the shaft that connects the compressor impeller and turbine. It also must contain a bearing system to suspend the shaft, allowing it to rotate at very high speed with minimal friction. For instance, in automotive applications the CHRA typically uses a thrust bearing or ball bearing lubricated by a constant supply of pressurized engine oil. The CHRA may also be considered "water-cooled" by having an entry and exit point for engine coolant to be cycled. Water-cooled models allow engine coolant to be used to keep the lubricating oil cooler, avoiding possible oil coking

Petroleum coke

Petroleum coke is a carbonaceous solid derived from oil refinery coker units or other cracking processes. Other coke has traditionally been derived from coal....

(the destructive distillation of the engine oil) from the extreme heat found in the turbine. The development of air-foil bearing

Foil bearing

Foil bearings, also known as foil-air bearings, are a type of air bearing. A shaft is supported by a compliant, spring-loaded foil journal lining. Once the shaft is spinning quickly enough, the working fluid pushes the foil away from the shaft so that there is no more contact...

s has removed this risk. Adaptation of turbochargers on naturally aspirated internal combustion engines, on either petrol or diesel, can yield power increases of 30% to 40%.

Variable geometry

Instead of using two turbochargers in different sizes, some engines use a single turbocharger, called variable-geometry or variable-nozzle turbos; these turbos use a set of vanes in the exhaust housing to maintain a constant gas velocity across the turbine, the same kind of control as used on power plant turbines. Such turbochargers have minimal lag like a small conventional turbocharger and can achieve full boost as low as 1,500 engine rpm, yet remain efficient as a large conventional turbocharger at higher engine speeds. In many setups, these turbos do not use a wastegate. The vanes are controlled by a membrane identical to the one on a wastegate, but the mechanism operates the variable vane system instead. These variable turbochargers are commonly used in diesel engines.

Wastegate

To manage the pressure of the air coming from the compressor (known as the "upper-deck air pressure"), the engine's exhaust gas flow is regulated before it enters the turbine with a wastegate

Wastegate

A wastegate is a valve that diverts exhaust gases away from the turbine wheel in a turbocharged engine system. Diversion of exhaust gases regulates the turbine speed, which in turn regulates the rotating speed of the compressor. The primary function of the wastegate is to regulate the maximum boost...

that bypasses excess exhaust gas entering the turbocharger's turbine. A wastegate

Wastegate

is the most common mechanical speed control system, and is often further augmented by an electronic or manual boost controller

Boost controller

A boost controller is a device to control the boost level produced in the intake manifold of a turbocharged or supercharged engine by affecting the air pressure delivered to the pneumatic and mechanical wastegate actuator...

. The main function of a wastegate is to allow some of the exhaust to bypass the turbine when the set intake pressure is achieved. This regulates the rotational speed of the turbine and thus the output of the compressor. The wastegate is opened and closed by the compressed air from the turbo and can be raised by using a solenoid

Solenoid

A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...

to regulate the pressure fed to the wastegate membrane. This solenoid can be controlled by Automatic Performance Control

Automatic Performance Control

Automatic Performance Control was the first engine knock and boost control system that was introduced on turbo charged Saab H engines in 1982 and was fitted to all subsequent 900 Turbos through 1993 , as well as 9000 Turbos through 1989.The APC allowed a higher compression ratio Automatic...

, the engine's electronic control unit

Electronic control unit

In automotive electronics, electronic control unit is a generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle....

or a boost control computer.

Most modern automotive engines have wastegates that are internal to the turbocharger, although some earlier engines (such as the Audi

Audi

Audi AG is a German automobile manufacturer, from supermini to crossover SUVs in various body styles and price ranges that are marketed under the Audi brand , positioned as the premium brand within the Volkswagen Group....

Inline-5 in the UrS4 and S6) have external wastegates. External wastegates are more accurate and efficient than internal wastegates, but are far more expensive, and thus are in general found only in racing cars (where precise control of turbo boost is a necessity and any efficiency increase is welcomed).

Aircraft waste-gates and their operation are similar to automotive installations, however there are notable differences as well. Even within aircraft applications there are 2 distinctions, military/performance and non-performance.

Anti-surge/dump/blow off valves

Turbocharged engines operating at wide open throttle and high rpm require a large volume of air to flow between the turbo and the inlet of the engine. When the throttle is closed compressed air will flow to the throttle valve without an exit (i.e., the air has nowhere to go).

This causes a surge that can raise the pressure of the air to a level that can damage the turbo. If the pressure rises high enough, a compressor stall

Compressor stall

A compressor stall is a situation of abnormal airflow resulting from a stall of the aerofoils within the compressor of a jet engine. Stall is found in dynamic compressors, particularly axial compressors, as used in jet engines and turbochargers for reciprocating engines.Compressor stalls result in...

will occur, where the stored pressurized air decompresses backward across the impeller and out the inlet. The reverse flow back across the turbocharger causes the turbine shaft to reduce in speed more quickly than it would naturally, possibly damaging the turbocharger. In order to prevent this from happening, a valve is fitted between the turbo and inlet, which vents off the excess air pressure. These are known as an anti-surge, diverter, bypass, blow-off valve (BOV), or dump valve. It is a pressure relief valve, and is normally operated by the vacuum in the intake manifold.

The primary use of this valve is to maintain the spinning of the turbocharger at a high speed. The air is usually recycled back into the turbo inlet (diverter or bypass valves) but can also be vented to the atmosphere (blow off valve). Recycling back into the turbocharger inlet is required on an engine that uses a mass-airflow fuel injection system, because dumping the excessive air overboard downstream of the mass airflow sensor will cause an excessively rich fuel mixture (this is because the mass-airflow sensor has already accounted for the extra air that is no longer being used). Valves that recycle the air will also shorten the time needed to re-spool the turbo after sudden engine deceleration, since the load on the turbo when the valve is active is much lower than it is if the air charge is vented to atmosphere.

Reliability

Turbochargers can be damaged by dirty or ineffective oiling systems, and most manufacturers recommend more frequent oil changes for turbocharged engines. Many owners and some companies recommend using synthetic oil

Synthetic oil

Synthetic oil is a lubricant consisting of chemical compounds that are artificially made . Synthetic lubricants can be manufactured using chemically modified petroleum components rather than whole crude oil, but can also be synthesized from other raw materials...

s, which tend to flow more readily when cold and do not break down as quickly as conventional oils. Because the turbocharger will heat when running, many recommend letting the engine idle for up to three minutes before shutting off the engine if the turbocharger was used shortly before stopping. This gives the oil and the lower exhaust temperatures time to cool the turbo rotating assembly, and ensures that oil is supplied to the turbocharger while the turbine housing and exhaust manifold are still very hot; otherwise coking

Coke (fuel)

Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...

of the lubricating oil trapped in the unit may occur when the heat soaks into the bearings, causing rapid bearing wear and failure when the car is restarted. Even small particles of burnt oil will accumulate and lead to choking the oil supply and failure. This problem is less pronounced in diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s, due to specifications of higher-quality oil.

A turbo timer

Turbo timer

A turbo timer is a device designed to keep an automotive engine running for a pre-specified period of time in order to automatically execute the cool-down period required to prevent premature turbo wear and failure...

can keep an engine running for a pre-specified period of time, to automatically provide this cool-down period. Oil coking is also eliminated by foil bearings. A more complex and problematic protective barrier against oil coking is the use of water-cooled bearing cartridges. The water boils in the cartridge when the engine is shut off and forms a natural recirculation to drain away the heat. Nevertheless, it is bad practice to shut the engine off while the turbo and manifold are still glowing with heat.

In custom applications utilizing tubular headers rather than cast iron

Cast iron

Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

manifolds, the need for a cooldown period is reduced because the lighter headers store much less heat than heavy cast iron manifolds.
Race cars

Auto racing

Auto racing is a motorsport involving the racing of cars for competition. It is one of the world's most watched televised sports.-The beginning of racing:...

often utilize an Anti-Lag System to completely eliminate lag at the cost of reduced turbocharger life.

Automotive turbochargers, diesel and gasoline

The turbocharger's small size and low weight have production and marketing advantage to vehicle manufacturers. By providing naturally aspirated and turbocharged versions of one engine, the manufacturer can offer two different power outputs with only a fraction of the development and production costs of designing and installing a different engine. Improvements to robustness, reliability and cooling may be required to cope with the extra power. These can include sodium-cooled exhaust valves, better metallurgy for pistons or connecting rods, and increased piston cooling by spraying engine oil underneath the piston. The compact nature of a turbocharger means that bodywork and engine compartment layout changes to accommodate the more powerful engine are not needed. The use of parts common to the two versions of the same engine reduces production and servicing costs.

Today, turbochargers are most commonly used on gasoline engines in high-performance automobiles and diesel engines in transportation and other industrial equipment. Small cars in particular benefit from this technology, as there is often little room to fit a large engine. Volvo

Volvo

AB Volvo is a Swedish builder of commercial vehicles, including trucks, buses and construction equipment. Volvo also supplies marine and industrial drive systems, aerospace components and financial services...

, Saab

Saab Automobile

Saab Automobile AB, better known as Saab , is a Swedish car manufacturer owned by Dutch automobile manufacturer Swedish Automobile NV, formerly Spyker Cars NV. It is the exclusive automobile Royal Warrant holder as appointed by the King of Sweden...

, Audi

Audi

, Volkswagen

Volkswagen

Volkswagen is a German automobile manufacturer and is the original and biggest-selling marque of the Volkswagen Group, which now also owns the Audi, Bentley, Bugatti, Lamborghini, SEAT, and Škoda marques and the truck manufacturer Scania.Volkswagen means "people's car" in German, where it is...

, and Subaru

Subaru

; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...

have produced turbocharged cars for many years; the turbo Porsche 944

Porsche 944

The Porsche 944 is a sports car built by Porsche from 1982 to 1991. It was built on the same platform as the 924, although 924 production continued through 1988. The 944 was intended to last into the 1990s, but major revisions planned for a 944 S3 model were eventually rolled into the 968 instead,...

's acceleration performance was very similar to that of the larger-engine non-turbo Porsche 928

Porsche 928

The Porsche 928 was a sports-GT car sold by Porsche AG of Germany from 1978 to 1995. Originally intended to replace the company's iconic 911, the 928 attempted to combine the power, poise, and handling of a sports car with the refinement, comfort, and equipment of a luxury sedan to create what some...

; and Chrysler Corporation built numerous turbocharged cars in the 1980s and 1990s. Buick also developed a turbocharged V-6 during the energy crisis in the late 1970s as a fuel-efficient alternative to the enormous eight-cylinder engines that powered the famously large cars and produced them through most of the next decade as a performance option. Recently, several manufacturers have returned to the turbocharger in an attempt to improve the tradeoff between performance and fuel economy by using a smaller turbocharged engine in place of a larger normally aspirated engine. The Ford EcoBoost engine

Ford EcoBoost engine

EcoBoost is a family of turbocharged and direct injected six-cylinder and four-cylinder gasoline engines produced by the Ford Motor Company. Engines equipped with EcoBoost technology are designed to deliver power and torque consistent with larger displacement, naturally aspirated engines while...

is one such design, along with Volkswagen Group's TSI/TFSI engines, such as the Twincharger

Twincharger

1.4 engine.

The first production turbocharged automobile engines came from General Motors in 1962. The Y-body

GM Y platform

The Y platform, or Y body, designation has been used twice by the General Motors Corporation to describe a series of vehicles all built on the same basic body and sharing many parts and characteristics...

Oldsmobile Cutlass

The Oldsmobile Cutlass is a line of automobiles made by the Oldsmobile division of General Motors. The Cutlass began as a unibody compact car, but saw its greatest success as a body-on-frame intermediate car....

Jetfire was fitted with a Garrett AiResearch

Garrett AiResearch

Garrett AiResearch was a manufacturer of turboprop engines and turbochargers, and a pioneer in numerous aerospace technologies. It was previously known as Aircraft Tool and Supply Company, Garrett Supply Company, AiResearch Manufacturing Company, or simply AiResearch...

turbocharger and the Chevrolet Corvair

Chevrolet Corvair

-First generation :The 1960 Corvair 500 and 700 series four-door sedans were conceived as economy cars offering few amenities in order to keep the price competitive, with the 500 selling for under $2,000...

Monza Spyder with a TRW

TRW

TRW Inc. was an American corporation involved in a variety of businesses, mainly aerospace, automotive, and credit reporting. It was a pioneer in multiple fields including electronic components, integrated circuits, computers, software and systems engineering. TRW built many spacecraft,...

turbocharger. At the Paris auto show in 1974, during the height of the oil crisis, Porsche introduced the 911 Turbo – the world’s first production sports car with an exhaust turbocharger and pressure regulator. This was made possible by the introduction of a wastegate to direct excess exhaust gases away from the exhaust turbine.

The first turbocharged diesel truck was produced by Schweizer Maschinenfabrik Saurer

Saurer

Adolph Saurer AG was a Arbon, Switzerland , based manufacturer of trucks and buses, under the Saurer and Berna brand names, and active between 1903 and 1982....

(Swiss Machine Works Saurer) in 1938.

The world's first production turbo diesel automobiles were the Garrett-turbocharged Mercedes 300SD

Mercedes-Benz W116

The Mercedes-Benz W116 was a series of flagship vehicles produced from September 1972 through 1979. The W116 automobiles were the first Mercedes-Benz models to be officially called S-Class, although earlier sedan models had already unofficially been designated with the letter 'S' - for...

and the Peugeot 604

Peugeot 604

The Peugeot 604 is an executive car produced by the French manufacturer Peugeot from 1975 to 1985. 153,252 examples of the 604 were sold during its 10-year production life. It was made in France and also by Kia in Korea....

, both introduced in 1978. Today, most automotive diesels are turbocharged.

1962 Oldsmobile Cutlass Jetfire
1962 Chevrolet Corvair Monza Spyder
1973 BMW 2002 Turbo
1974 Porsche 911 Turbo
1978 Buick Regal
1978 Saab 99
1978 Peugeot 604 turbodiesel
1978 Mercedes-Benz 300SD turbodiesel (United States/Canada)
1979 Alfa Romeo Alfetta
Alfa Romeo Alfetta
Alfa Romeo GTV redirects here. For 916 series GTV see Alfa Romeo GTV & SpiderThe Alfa Romeo Alfetta is an Italian rear-wheel drive executive saloon car and fastback coupé produced from 1972 until 1987 by Alfa Romeo...

GTV 2000 Turbodelta
1980 Mitsubishi Lancer GT Turbo
1980 Pontiac Firebird
1980 Renault 5 Turbo
1981 Volvo 240-series Turbo

Multiple turbochargers

Parallel

Some engines, such as V-type engines

V engine

A V engine, or Vee engine is a common configuration for an internal combustion engine. The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft...

, utilize two identically sized but smaller turbos, each fed by a separate set of exhaust streams from the engine. The two smaller turbos produce the same (or more) aggregate amount of boost as a larger single turbo, but since they are smaller they reach their optimal RPM, and thus optimal boost delivery, more quickly. Such an arrangement of turbos is typically referred to as a parallel twin-turbo system. The first production automobile with parallel twin turbochargers was the Maserati Biturbo

Maserati Biturbo

The Maserati Biturbo is a sports car introduced by Maserati in 1981. The Biturbo is a two-door, four-seater notchback coupé featuring, as the name implies, a two-litre V6 engine with two turbochargers and a luxurious interior.The car was designed by Pierangelo Andreani, an engineer from the De...

of the early 1980s. Later such installations include Porsche 911 TT

Porsche 911

The Porsche 911 is a luxury 2-door sports coupe made by Porsche AG of Stuttgart, Germany. It has a distinctive design, rear-engined and with independent rear suspension, an evolution of the swing axle on the Porsche 356. The engine was also air-cooled until the introduction of the Type 996 in 1998...

, Nissan GT-R

Nissan GT-R

The Nissan GT-R is a sports car produced by Nissan released in Japan on December 6, 2007, the United States on July 4, 2008, and the rest of the world in March 2009.-History:...

, Mitsubishi 3000GT VR-4

Mitsubishi GTO

The Mitsubishi GTO is a sports car built by Japanese automaker Mitsubishi Motors between 1990 and 2001. In most export markets it was rebadged as a Mitsubishi 3000GT. It was also sold by Chrysler in North America as a Dodge Stealth captive import from the 1991 to 1996 model years with only minor...

, Nissan 300ZXTT, Audi RS6

Audi RS6

The Audi RS6 quattro, commonly referred to as the RS6, is the highest performing version, and top-of-the-line specification of the Audi A6, positioned above the Audi S6...

, and BMW E90.

Sequential

Some car makers combat lag by using two small turbos. A typical arrangement for this is to have one turbo active across the entire rev range of the engine and one coming on-line at higher RPM. Below this RPM, both exhaust and air inlet of the secondary turbo are closed. Being individually smaller they do not suffer from excessive lag and having the second turbo operating at a higher RPM range allows it to get to full rotational speed before it is required. Such combinations are referred to as a sequential twin-turbo. Porsche first used this technology in 1985 in the Porsche 959

Porsche 959

The Porsche 959 is a sports car manufactured by Porsche from 1986 to 1989, first as a Group B rally car and later as a legal production car designed to satisfy FIA homologation regulations requiring that a minimum number of 200 street legal units be built....

. Sequential twin-turbos are usually much more complicated than a single or parallel twin-turbo systems because they require what amounts to three sets of intake and waste gate pipes for the two turbochargers as well as valves to control the direction of the exhaust gases. Many new diesel engines use this technology not only to eliminate lag but also to reduce fuel consumption and reduce emissions.

Aircraft turbochargers

A natural use of the turbocharger is with aircraft engine

Aircraft engine

An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...

s. As an aircraft climbs to higher altitudes the pressure of the surrounding air quickly falls off. At 5,486 m

Metre

(18,000 ft), the air is at half the pressure of sea level, and the airframe experiences only half the aerodynamic drag

Drag equation

In fluid dynamics, the drag equation is a practical formula used to calculate the force of drag experienced by an object due to movement through a fully enclosing fluid....

. However, since the charge in the cylinders is being pushed in by this air pressure, it means that the engine will normally produce only half-power at full throttle at this altitude. Pilots would like to take advantage of the low drag at high altitudes in order to go faster, but a naturally aspirated engine will not produce enough power at the same altitude to do so.

A turbocharger remedies this problem by compressing the air back to sea-level pressures, or even much higher, in order to produce rated power at high altitude. Since the size of the turbocharger is chosen to produce a given amount of pressure at high altitude, the turbocharger is over-sized for low altitude. The speed of the turbocharger is controlled by a wastegate

Wastegate

. Early systems used a fixed wastegate, resulting in a turbocharger that functioned much like a supercharger. Later systems utilized an adjustable wastegate, controlled either manually by the pilot or by an automatic hydraulic or electric system. When the aircraft is at low altitude the wastegate is usually fully open, venting all the exhaust gases overboard. As the aircraft climbs and the air density drops, the wastegate must continuously close in small increments to maintain full power. The altitude at which the wastegate is fully closed and the engine is still producing full rated power is known as the critical altitude. When the aircraft climbs above the critical altitude, engine power output will decrease as altitude increases just as it would in a naturally aspirated engine.

With older supercharged aircraft, the pilot must continually adjust the throttle to maintain the required manifold pressure during ascent or descent. The pilot must also take great care to avoid overboosting the engine and causing damage, especially during emergencies such as go-around

Go-around

A go-around is an aborted landing of an aircraft that is on final approach.- Origin of the term :The term arises from the traditional use of traffic patterns at airfields. A landing aircraft will first join the circuit pattern and prepare for landing in an orderly fashion...

s. In contrast, modern turbocharger systems use an automatic wastegate

Wastegate

, which controls the manifold pressure within parameters preset by the manufacturer. For these systems, as long as the control system is working properly and the pilot's control commands are smooth and deliberate, a turbocharger will not overboost the engine and damage it.

Yet the majority of World War II engines used superchargers, because they maintained three significant manufacturing advantages over turbochargers, which were larger, involved extra piping, and required exotic high-temperature materials in the turbine and pre-turbine section of the exhaust system. The size of the piping alone is a serious issue; American fighters Vought F4U and Republic P-47 used the same engine but the huge barrel-like fuselage of the latter was, in part, needed to hold the piping to and from the turbocharger in the rear of the plane. Turbocharged piston engines are also subject to many of the same operating restrictions as gas turbine engines. Pilots must make smooth, slow throttle adjustments to avoid overshooting their target manifold pressure. The fuel mixture must often be adjusted far on the rich side of stoichiometric combustion needs to avoid pre-detonation in the engine when running at high power settings. In systems using a manually operated wastegate, the pilot must be careful not to exceed the turbocharger's maximum RPM. Turbocharged engines require a cooldown period after landing to prevent cracking of the turbo or exhaust system from thermal shock. Turbocharged engines require frequent inspections of the turbocharger and exhaust systems for damage due to the increased heat, increasing maintenance costs.

Today, most general aviation

General aviation

General aviation is one of the two categories of civil aviation. It refers to all flights other than military and scheduled airline and regular cargo flights, both private and commercial. General aviation flights range from gliders and powered parachutes to large, non-scheduled cargo jet flights...

aircraft are naturally aspirated. The small number of modern aviation piston engines designed to run at high altitudes in general use a turbocharger or turbo-normalizer system rather than a supercharger. The change in thinking is largely due to economics. Aviation gasoline was once plentiful and cheap, favoring the simple but fuel-hungry supercharger. As the cost of fuel has increased, the supercharger has fallen out of favor.

Turbocharged aircraft often occupy a performance range between that of normally aspirated piston-powered aircraft and turbine-powered aircraft. The increased maintenance costs of a turbocharged engine are considered worthwhile for this purpose, as a turbocharged piston engine is still far cheaper than any turbine engine.

Marine and land-based diesel turbochargers

Turbocharging while common on diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s in automobiles, truck

Truck

A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

s, tractor

Tractor

A tractor is a vehicle specifically designed to deliver a high tractive effort at slow speeds, for the purposes of hauling a trailer or machinery used in agriculture or construction...

s, and boats is also common in heavy machinery such as locomotives, ship

Ship

Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

s, and auxiliary power generation.

Turbocharging can dramatically improve an engine's specific power
Specific power
In physics and engineering, surface power density or sometimes simply specific power is power per unit area.-Applications:* The intensity of electromagnetic radiation can be expressed in W/m2...

and power-to-weight ratio
Power-to-weight ratio
Power-to-weight ratio is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power sources...

, performance characteristics, which are normally poor in non-turbocharged diesel engines.
Diesel engines have no detonation
Engine knocking
Knocking in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.The...

because diesel fuel is injected at the end of the compression stroke, ignited by compression heat. Because of this, diesel engines can use much higher boost pressures than spark ignition engines, limited only by the engine's ability to withstand the additional heat and pressure.

Motorsport and performance turbochargers

It is also important to understand that a gasoline engine's design and compression ratio effect the maximum possible boost. To obtain more power from higher boost levels and maintain reliability, many engine components have to be replaced or upgraded such as the fuel pump, fuel injectors, pistons, connecting rods, crankshafts, valves, head-gasket, and head bolts. The maximum possible boost depends on the fuel's octane rating and the inherent tendency of any particular engine toward detonation

Engine knocking

. Premium gasoline or racing gasoline can be used to prevent detonation within reasonable limits. Ethanol, methanol, liquefied petroleum gas (LPG) and compressed natural gas (CNG) allow higher boost than gasoline, because of their higher resistance to autoignition (lower tendency to knock). Diesel engines can also tolerate much higher levels of boost pressure than Otto cycle

Otto cycle

An Otto cycle is an idealized thermodynamic cycle which describes the functioning of a typical reciprocating piston engine, the thermodynamic cycle most commonly found in automobile engines....

engines, because only air is being compressed during the compression phase, and fuel is injected later, removing the knocking issue entirely.

Aircraft engineer Frank Halford

Frank Halford

Major Frank Bernard Halford CBE FRAeS was an English aircraft engine designer.-Career:Educated at Felsted, In 1913 he left the University of Nottingham before graduating to learn to fly at Brooklands and Bristol Flying School and became a flight instructor using Bristol Boxkites.He served in the...

experimented with turbocharging in his modified Aston Martin

Aston Martin

Aston Martin Lagonda Limited is a British manufacturer of luxury sports cars, based in Gaydon, Warwickshire. The company name is derived from the name of one of the company's founders, Lionel Martin, and from the Aston Hill speed hillclimb near Aston Clinton in Buckinghamshire...

racing car the Halford Special, but it is unclear whether or not his efforts were successful. The first successful application of turbocharging in automotive racing appears to have been in 1952 when Fred Agabashian

Fred Agabashian

Fred Agabashian was an Armenian-American racer of midget cars and Indy cars.-Midget car:...

in the diesel-powered Cummins
Cummins
Cummins Inc. is a Fortune 500 corporation that designs, manufactures, distributes and services engines and related technologies, including fuel systems, controls, air handling, filtration, emission control and electrical power generation systems...

Special qualified for pole position at the Indianapolis 500

Indianapolis 500

The Indianapolis 500-Mile Race, also known as the Indianapolis 500, the 500 Miles at Indianapolis, the Indy 500 or The 500, is an American automobile race, held annually, typically on the last weekend in May at the Indianapolis Motor Speedway in Speedway, Indiana...

and led for 175 miles (281.6 km) before ingested tire shards disabled the compressor section of the Elliott turbocharger. Offenhauser

Offenhauser

Offenhauser was an American racing engine manufacturer that operated from 1933 to 1983.The Offenhauser engine, familiarly known as the "Offy", was developed by Fred Offenhauser and his employer Harry Arminius Miller, after maintaining and repairing a 1913 Peugeot Grand Prix car of the type which...

's turbocharged engines returned to Indianapolis in 1966, with victories coming in 1968 using a Garrett AiResearch

Garrett AiResearch

turbocharger. The Offenhauser turbo peaked at over 1000 hp in 1973, which led USAC

United States Automobile Club

The United States Auto Club is one of the sanctioning bodies of auto racing in the United States. From 1956 to 1979, the USAC sanctioned the United States National Championship, and from 1956 to 1997 the organization sanctioned the Indianapolis 500...

to limit boost pressure. In their turn, Porsche

Porsche

Porsche Automobil Holding SE, usually shortened to Porsche SE a Societas Europaea or European Public Company, is a German based holding company with investments in the automotive industry....

dominated the Can-Am series with a 1100 hp 917/30

Porsche 917

The Porsche 917 is a racecar that gave Porsche its first overall wins at the 24 Hours of Le Mans in 1970 and 1971. Powered by the Type 912 flat-12 engine of 4.5, 4.9, or 5 litres, the 917/30 variant was capable of a 0- time of 2.3 seconds, 0– in 5.3 seconds, and a top speed of over .There are 6...

. Turbocharged cars dominated the 24 Hours of Le Mans

24 Hours of Le Mans

The 24 Hours of Le Mans is the world's oldest sports car race in endurance racing, held annually since near the town of Le Mans, France. Commonly known as the Grand Prix of Endurance and Efficiency, race teams have to balance speed against the cars' ability to run for 24 hours without sustaining...

between 1976 and 1988, and then from 2000-2007.
In Formula One

Formula One

Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...

, in the so called "Turbo Era" of until , Renault

Renault F1

Lotus Renault GP, formerly the Renault F1 Team, is a British Formula One racing team. The Oxfordshire-based team can trace its roots back through the Benetton team of the late 1980s and 1990s to the Toleman team of the early 1980s. Renault had also competed in various forms since , before taking...

, Honda

Honda F1

Honda Racing F1 Team was a Formula One team run by Japanese car manufacturer Honda, from 1964 to 1968 and from 2006 to 2008. Honda's involvement in F1 began with the 1964 season; their withdrawal in 1968 was precipitated by the death of Honda driver Jo Schlesser during the 1968 French Grand Prix. ...

, BMW

BMW

Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...

, and Ferrari

Ferrari

Ferrari S.p.A. is an Italian sports car manufacturer based in Maranello, Italy. Founded by Enzo Ferrari in 1929, as Scuderia Ferrari, the company sponsored drivers and manufactured race cars before moving into production of street-legal vehicles as Ferrari S.p.A. in 1947...

produced engines with a capacity of 1500 cc able to generate 1000 hp. Renault was the first manufacturer to apply turbo technology in F1. The project's high cost was compensated for by its performance, and led other engine manufacturers to follow suit. Turbocharged engines dominated and ended the Cosworth DFV

Cosworth DFV

The DFV is an internal combustion engine that was originally produced by Cosworth for Formula One motor racing. Named Four Valve because of the four valves per cylinder, and Double as it was a V8 development of the earlier, four-cylinder FVA , making it a Double Four Valve engine...

era in the mid-1980s. However, the FIA

Fédération Internationale de l'Automobile

The Fédération Internationale de l'Automobile is a non-profit association established as the Association Internationale des Automobile Clubs Reconnus on 20 June 1904 to represent the interests of motoring organisations and motor car users...

decided turbochargers were making the sport too dangerous and expensive. In , FIA decided to limit the maximum boost before the technology was banned for .

In land speed racing, an 1800 hp twin-turbocharged Pontiac GTA developed by Gale Banks

Gale Banks

Gale Banks is a hot rodder, drag racer, and automotive mechanical and electrical engineer who grew up in Lynnwood, California. From 1966 through 2007, his cars, trucks and dragsters have set numerous drag racing and land-speed records, as certified by the NHRA and FIA respectively...

of Southern California

Southern California

Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...

, set a land speed record for the "World's Fastest Passenger Car" of 277 mi/h. This event was chronicled at the time in a 1987 cover story published by Autoweek
AutoWeek
AutoWeek is a fortnightly automotive enthusiast publication based in Detroit, Michigan. One of 32 titles published by Crain Communications Inc, its parent company, AutoWeek is unique as the only consumer title among its sister publications....

magazine. Gale Banks Engineering

Gale banks engineering

Gale Banks Engineering and its four divisions , are companies created by Southern California hot rodder and automobile engineer, Gale Banks. These companies design, engineer and build high performance parts for the automobile and marine aftermarket and military customers...

also built and raced several diesel-powered machines, including what Banks erroneously calls the "World's Fastest Diesel Truck," a street-legal 735 hp Dodge Dakota

Dodge Dakota

The Dodge Dakota is a mid-size pickup truck from Chrysler's Ram division. From its introduction through 2009, it was marketed by Dodge. The first Dakota was introduced in 1986 as a 1987 model alongside the redesigned Dodge Ram 50...

pick-up that towed its own trailer to the Bonneville Salt Flats and then set an official FIA record of 217 mph (349.2 km/h) with a one-way top speed of 222 mph (357.3 km/h). The truck also showed the fuel economy of a turbocharged diesel engine by averaging 21.2-mpg on the Hot Rod Power Tour.
If it ran 50 mi/h faster, it would almost match the actual fastest diesel truck, the "Phoenix" of R. B. Slagle and Carl Heap.

Modern Group N Rally cars are forced by the rules to use a 33 mm (1.3 in) restrictor at the compressor inlet, which effectively limits the maximum boost (pressure above atmospheric) that the cars can achieve at high rpm. Of note is that, at low rpm, they can reach boost pressures of above 22 psi (1.5 bar).

In rallying

Rallying

Rallying, also known as rally racing, is a form of auto racing that takes place on public or private roads with modified production or specially built road-legal cars...

, turbocharged engines of up to 2000 cc have long been the preferred motive power for the Group A/N World Rally Car

World Rally Car

World Rally Car is a term used to describe racing automobiles built to the specification set by the FIA, the international motorsports governing body, and used to compete in the outright class of the World Rally Championship...

competitors, due to the exceptional power-to-weight ratios attainable. This combines with the use of vehicles with relatively small bodyshells for maneuverability and handling. As turbo outputs rose to levels similar to F1's category, rather than banning the technology, FIA restricted turbo inlet diameter (currently 34 mm).

Motorcycle turbochargers

Using turbochargers to gain performance without a large gain in weight was very appealing to the Japanese factories in the 1980s. The first example of a turbocharged bike is the 1978 Kawasaki

Kawasaki Heavy Industries

is an international corporation based in Japan. It has headquarters in both Chūō-ku, Kobe and Minato, Tokyo.The company is named after its founder Shōzō Kawasaki and has no connection with the city of Kawasaki, Kanagawa....

Z1R TC. It used a Rayjay ATP turbo kit to build 0.35 bar (5 lb) of boost, bringing power up from c. 90 hp to c. 105 hp. However, it was only marginally faster than the standard model.

In 1982, Honda released the CX500T featuring a carefully developed turbo (as opposed to the Z1-R's bolt-on approach). It has a rotation speed of 200,000 rpm. The development of the CX500T was riddled with problems; due to its being a V-twin

V-twin

A V-twin engine is a two-cylinder internal combustion engine where the cylinders are arranged in a V configuration.- Crankshaft configuration :Most V-twin engines have a single crankpin, which is shared by both connecting rods...

engine, the intake periods in the engine rotation are staggered, leading to periods of high intake and long periods of no intake at all. Designing around these problems increased the price of the bike, and the performance still was not as good as the cheaper CB900 (a 16 valve in-line four). During these years, Kawasaki

Kawasaki

-Places:*Kawasaki, Kanagawa, Japanese city**Kawasaki-ku, Kawasaki, a ward in Kawasaki, Kanagawa***Kawasaki Stadium, a multi-sport stadium***Kawasaki Station, a train station***Keikyū Kawasaki Station, a train station*Kawasaki, Fukuoka, Japanese town...

produced the GPz750 Turbo

Kawasaki GPZ750 Turbo

The Kawasaki GPz750 Turbo was a sportbike manufactured from late 1983 to 1985, with two model years - the 1984 E1 and the 1985 E2. Differences were minor, a twin "push/pull" throttle cable for the E2 and different brake caliper stickers...

, Suzuki

Suzuki

is a Japanese multinational corporation headquartered in Hamamatsu, Japan that specializes in manufacturing compact automobiles and 4x4 vehicles, a full range of motorcycles, all-terrain vehicles , outboard marine engines, wheelchairs and a variety of other small internal combustion engines...

produced the XN85

Suzuki XN85

The Suzuki XN85, released in early 1983, was a turbocharged motorcycle. It was designed as a sportbike. The name came from the fact that it produced 85 hp. It featured the first factory 16-inch front wheel, which was previously seen only on race bikes...

, and Yamaha

Yamaha

Yamaha may refer to:* Yamaha Corporation, a Japanese company with a wide range of products and services** Yamaha Motor Company, a Japanese motorized vehicle-producing company...

produced the Seca Turbo. The GPz750 Turbo and XN85 were fuel-injected, whereas the Yamaha Seca Turbo relied on pressurized carburetors.

Since the mid-1980s, no manufactures have produced turbocharged motorcycles making these bikes a bit of an educational experience; as of 2007, no factories offer turbocharged motorcycles (although the Suzuki

Suzuki

B-King prototype featured a supercharged Hayabusa engine). The Dutch manufacturer EVA motorcycles builds a small series of turbocharged diesel motorcycle with an 800cc smart cdi engine.

Manufacturers of turbochargers

ABB Turbo Systems
Asea Brown Boveri
ABB is a Swiss-Swedish multinational corporation headquartered in Zürich, Switzerland, and best known for its robotics. ABB operates mainly in the power and automation technology areas. It ranked 143rd in Forbes Ranking ....
BorgWarner Turbo Systems
BorgWarner
BorgWarner Inc. is a United States-based worldwide automotive industry components and parts supplier. It is primarily known for its powertrain products, which include manual and automatic transmissions and transmission components, , turbochargers, engine valve timing system...
Bosch Mahle Turbo Systems (Joint Venture
Joint venture
A joint venture is a business agreement in which parties agree to develop, for a finite time, a new entity and new assets by contributing equity. They exercise control over the enterprise and consequently share revenues, expenses and assets...

of Bosch
Robert Bosch GmbH
Robert Bosch GmbH is a multinational engineering and electronics company headquartered in Gerlingen, near Stuttgart, Germany. It is the world's largest supplier of automotive components...

and Mahle
Mahle GmbH
Mahle GmbH is one of the 30 largest automotive suppliers worldwide. As the leading manufacturer of components and systems for combustion engines and its periphery, the Mahle Group is among the top three systems suppliers worldwide for piston systems, cylinder components, valve train systems, air...

)
Caterpillar
Caterpillar Inc.
Caterpillar Inc. , also known as "CAT", designs, manufactures, markets and sells machinery and engines and sells financial products and insurance to customers via a worldwide dealer network. Caterpillar is the world's largest manufacturer of construction and mining equipment, diesel and natural gas...
Cummins Turbo Technologies (Holset)
Hitachi Warner Turbo Systems (Joint Venture of Hitachi
Hitachi
Hitachi is a multinational corporation specializing in high-technology.Hitachi may also refer to:*Hitachi, Ibaraki, Japan*Hitachi province, former province of Japan*Prince Hitachi and Princess Hitachi, members of the Japanese imperial family...

and BorgWarner
BorgWarner
BorgWarner Inc. is a United States-based worldwide automotive industry components and parts supplier. It is primarily known for its powertrain products, which include manual and automatic transmissions and transmission components, , turbochargers, engine valve timing system...

)
Honeywell Turbo Technologies
Honeywell
Honeywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....

(previously Garrett AiResearch
Garrett AiResearch
Garrett AiResearch was a manufacturer of turboprop engines and turbochargers, and a pioneer in numerous aerospace technologies. It was previously known as Aircraft Tool and Supply Company, Garrett Supply Company, AiResearch Manufacturing Company, or simply AiResearch...

)
IHI Corporation
Komatsu
Komatsu
orKomatsu is a multinational corporation that manufactures construction, mining, and military equipment, Industrial equipments such as press machines, lasers, and thermoelectric generators.Its headquarters is at 2-3-6, Akasaka, Minato, Tokyo, Japan...
MAN Diesel
Mitsubishi Heavy Industries
Mitsubishi Heavy Industries
, or MHI, is a Japanese company. It is one of the core companies of Mitsubishi Group.-History:In 1870 Yataro Iwasaki, the founder of Mitsubishi took a lease of Government-owned Nagasaki Shipyard. He named it Nagasaki Shipyard & Machinery Works, and started the shipbuilding business on a full scale...
NAPIER Turbochargers
Napier & Son
D. Napier & Son Limited was a British engine and pre-Great War automobile manufacturer and one of the most important aircraft engine manufacturers in the early to mid-20th century...
Turbo Energy Ltd (Joint venture of Borg warner and Brakes India)
Voith Turbo

External links

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