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{{Short description|Exhaust-powered forced-induction device for engines}}
{{redirect|Turbo}}
{{Use dmy dates|date=October 2019}}
]-supported turbocharger cutaway made by ]]
{{Redirect|turbo|other uses}}
]


In an ], a '''turbocharger''' (also known as a '''turbo''' or a '''turbosupercharger''') is a ] 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 ].<ref>{{cite web|last=Nice |first=Karim |url=http://auto.howstuffworks.com/turbo.htm |title=How Turbochargers Work |publisher=Auto.howstuffworks.com |date=4 December 2000 |access-date=1 June 2012}}</ref><ref name="reviews.cnet.com"> {{webarchive|url=https://web.archive.org/web/20110326015904/http://reviews.cnet.com/8301-13746_7-20045466-48.html|date=26 March 2011}}</ref>
A '''turbocharger''' (short for turbo-supercharger) is an ] driven ] device used in ] to improve ] performance by forcing compressed air into the ]s, allowing more fuel to be burned, resulting in a larger power output.


The current categorisation is that a turbocharger is powered by the kinetic energy of the exhaust gases, whereas a ] is mechanically powered (usually by a belt from the engine's crankshaft).<ref>{{cite book |title=Automotive handbook |date=2004 |publisher=Robert Bosch |location=Stuttgart |isbn=0-8376-1243-8 |pages=528 |edition=6th |url=https://books.google.com/books?id=_t1oPwAACAAJ |access-date=6 June 2022}}</ref> However, up until the mid-20th century, a turbocharger was called a "turbosupercharger" and was considered a type of supercharger.<ref>{{cite web|url=http://rwebs.net/avhistory/opsman/geturbo/geturbo.htm |title=The Turbosupercharger and the Airplane Power Plant |publisher=Rwebs.net |date=1943-12-30 |access-date=2010-08-03}}</ref>
==Working principle==


== History ==
A turbocharger consists of a ] and a ] linked by a shared axis. The turbine inlet receives exhaust gases from the engine exhaust manifold causing the turbine wheel to rotate. This rotation drives the compressor, compressing ambient air and delivering it to the air intake of the engine.


Prior to the invention of the turbocharger, ] was only possible using mechanically-powered ]s. Use of superchargers began in 1878, when several supercharged two-stroke gas engines were built using a design by Scottish engineer ].<ref>{{cite book|title=Encyclopedia of the History of Technology |year=1990 |publisher=Routledge |location=London |isbn=0-203-19211-7 |page=315 |url=https://archive.org/details/encyclopaediaofh00mcne/page/315|editor=Ian McNeil}}</ref> Then in 1885, ] patented the technique of using a gear-driven pump to force air into an internal combustion engine.<ref>{{cite web |url=http://www.calaisturbo.org/history-of-the-supercharger.php |title=History of the Supercharger |access-date=30 June 2011 |archive-date=13 July 2015 |archive-url=https://web.archive.org/web/20150713170831/http://www.calaisturbo.org/history-of-the-supercharger.php |url-status=dead }}</ref>
The objective of a turbocharger is to improve upon the size-to-output efficiency of an engine by solving for one of its cardinal limitations. A ] automobile engine uses only the downward stroke of a piston to create an area of low pressure in order to draw air into the cylinder. Since the number of air and fuel molecules determine the potential energy available to force the piston down on the combustion stroke, and because of the relatively constant pressure of the atmosphere, there ultimately will be a limit to the amount of air and consequently fuel filling the ]. This ability to fill the cylinder with air is its ]. Since the turbocharger increases the pressure at the point where air is entering the cylinder, and the amount of air brought into the cylinder is largely a function of time and pressure, more air will be drawn in as the pressure increases. Thus, the intake pressure can be controllably increased by the turbocharger.


The 1905 patent by ], a Swiss engineer working at ] is often considered the birth of the turbocharger.<ref>{{cite web |url=https://new.abb.com/turbocharging/110-years-of-turbocharging |title=Celebrating 110 years of turbocharging |publisher=ABB |access-date=22 July 2021 }}</ref><ref name="newatlas.com">{{cite web |title=The turbocharger turns 100 years old this week |url=https://newatlas.com/go/4848/ |website=www.newatlas.com |access-date=20 September 2019 |language=en |date=18 November 2005}}</ref><ref>{{cite book |title=Porsche Turbo: The Full History |first=Peter |last=Vann |publisher=MotorBooks International |date=11 July 2004 |isbn=9780760319239}}</ref> This patent was for a compound ] with an exhaust-driven axial flow ] and compressor mounted on a common shaft.<ref name="Miller">{{cite book |last1=Miller |first1=Jay K. |title=Turbo: Real World High-Performance Turbocharger Systems |date=2008 |publisher=CarTech Inc |page=9 |isbn=9781932494297 |url=https://books.google.com/books?id=hhiVyuHS76UC |access-date=20 September 2019 |language=en}}</ref><ref>{{patent|DE|204630|"Verbrennungskraftmaschinenanlage"}}</ref> 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.<ref name="aeplus.com page 1">{{cite web |title=Alfred Büchi the inventor of the turbocharger - page 1 |url=http://ae-plus.com/milestones/alfred-bchi-the-inventor-of-the-turbocharger/page:1 |website=www.ae-plus.com |url-status=dead |archive-url=https://web.archive.org/web/20150405003800/http://ae-plus.com/milestones/alfred-bchi-the-inventor-of-the-turbocharger/page:1 |archive-date=5 April 2015}}</ref><ref name="cummins.ru">{{cite web |title=Turbocharger History |url=http://www.cummins.ru/en/components/turbo-technologies/turbocharger-history |website=www.cummins.ru |access-date=20 September 2019}}</ref> However, the prototype was not reliable and did not reach production.<ref name="aeplus.com page 1"/> Another early patent for turbochargers was applied for in 1916 by French steam turbine inventor ], for their intended use on the Renault engines used by French fighter planes.<ref name="Miller"/><ref name="Air & Space, Hill Climb" >{{cite journal|url=http://www.airspacemag.com/history-of-flight/climb.html?c=y&page=1 |journal=Air & Space Magazine |title=Hill Climb |access-date=2 August 2010 }}</ref> Separately, testing in 1917 by the ] (NACA) and ] 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 {{convert|4250|m|ft|0|abbr=on}} above sea level.<ref name="Miller"/> The testing was conducted at ] in the United States using the ] aircraft engine.<ref name="Air & Space, Hill Climb" />
The application of a compressor to increase pressure at the point of cylinder air intake is often referred to as ]. ]s operate in the same fashion as a turbo; however, the energy to spin the compressor is taken from the rotating output energy of the engine's crankshaft as opposed to exhaust gas. For this reason turbochargers are ideally more efficient, since their turbines are actually heat engines, converting some of the ] from the exhaust gas that would otherwise be wasted, into useful work. Contrary to popular belief, this is not totally "free energy," as it always creates some amount of exhaust backpressure which the engine must overcome. Superchargers use output energy to achieve a net gain, which is at the expense of some of the engine's total output.


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 ], under the supervision of Alfred Büchi, to SLM, ] in Winterthur.<ref>{{Cite book |last=Jenny |first=Ernst |url=https://books.google.com/books?id=hl58zgEACAAJ |title="The" BBC Turbocharger: A Swiss Success Story |date=1993 |publisher=Birkhäuser Verlag |pages=46 |language=en}}</ref> This was followed very closely in 1925, when Alfred Büchi successfully installed turbochargers on ten-cylinder diesel engines, increasing the power output from {{convert|1750|to|2500|hp|kW|disp=flip}}.<ref name="ae-plus.com page 2">{{cite web |title=Alfred Büchi the inventor of the turbocharger - page 2 |url=http://ae-plus.com/milestones/alfred-bchi-the-inventor-of-the-turbocharger/page:2 |website=www.ae-plus.com |archive-url=https://web.archive.org/web/20170929135541/http://ae-plus.com/milestones/alfred-bchi-the-inventor-of-the-turbocharger/page:2 |archive-date=29 September 2017}}</ref><ref>Compressor Performance: Aerodynamics for the User. M. Theodore Gresh. Newnes, 29 March 2001</ref><ref>Diesel and gas turbine progress, Volume 26. Diesel Engines, 1960</ref> This engine was used by the German Ministry of Transport for two large passenger ships called the ''Preussen'' and {{ship|German minelayer|Hansestadt Danzig||2}}. The design was licensed to several manufacturers and turbochargers began to be used in marine, railcar and large stationary applications.<ref name="cummins.ru" />
==History==
The turbocharger was invented by ] engineer Alfred Buchi, who had been working on steam turbines. His patent for the internal combustion turbocharger was applied for in 1905. ] ships and locomotives with turbochargers began appearing in the ].


Turbochargers were used on several aircraft engines during World War II, beginning with the ] in 1938, which used turbochargers produced by General Electric.<ref name="Miller"/><ref>{{cite web|url=https://aviationshoppe.com/manuals/wwii_aircraft_superchargers/wwii_aircraft_turbosupercharger.html|title=World War II - General Electric Turbosupercharges|website=aviationshoppe.com}}</ref> Other early turbocharged airplanes included the ], ], ] and experimental variants of the ].
One of the first applications of a turbocharger to a non-Diesel engine came when ] engineer, Sanford Moss attached a turbo to a ] '']'' aircraft engine. The engine was tested at ] in ] at 14,000 feet to demonstrate that it could eliminate the power losses usually experienced in internal combustion engines as a result of altitude.


The first practical application for trucks was realized by Swiss truck manufacturing company ] in the 1930s. BXD and BZD engines were manufactured with optional turbocharging from 1931 onwards.<ref>{{cite web |url=http://www.saureroldtimer.ch/5000geschichte/5200chronosaurer/index.html |title=Saurer Geschichte |language=German |location=German |archive-url=https://web.archive.org/web/20100304062804/http://www.saureroldtimer.ch/5000geschichte/5200chronosaurer/index.html |archive-date=4 March 2010}}</ref> The Swiss industry played a pioneering role with turbocharging engines as witnessed by Sulzer, Saurer and ].<ref>Ernst Jenny: "Der BBC-Turbolader." Birkhäuser, Basel, 1993, ISBN 978-3-7643-2719-4. ], May 26, 1993, p. 69.</ref><ref>{{patent|US|4838234|Mayer, Andreas: "Free-running pressure wave supercharger"}}, issued 1989-07-13, assigned to BBC Brown Boveri AG, Baden, Switzerland</ref>
Turbochargers were first used in production aircraft engines in the 1930s prior to ]. The primary purpose behind most aircraft-based applications was to increase the altitude at which the airplane can fly, by compensating for the lower ] present at high altitude. Aircraft such as the ], ] and ] all used exhaust driven "turbo-superchargers" to increase high altitude engine power. It is important to note that the majority of turbosupercharged aircraft engines utilized both a gear-driven ] and a turbocharger.


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.<ref name="newatlas.com"/><ref name="cummins.ru"/> The first turbocharged cars were the short-lived ] and the ], both introduced in 1962.<ref>{{cite news |last=Culmer |first=Kris |date=8 March 2018 |title=Throwback Thursday 1962: the Oldsmobile Jetfire explained |url=https://www.autocar.co.uk/car-news/anything-goes-throwback-thursday/throwback-thursday-1962-oldsmobile-jetfire-explained |newspaper=] |access-date=15 April 2022}}</ref><ref name="bwauto.com">{{cite web |title=History |url=http://www.turbos.bwauto.com/en/products/turbochargerHistory.aspx |website=www.bwauto.com |access-date=20 September 2019}}</ref> Greater adoption of turbocharging in passenger cars began in the 1980s, as a way to increase the performance of smaller ] engines.<ref name="Miller"/>
Turbo-Diesel trucks were produced in Europe and America (notably by ]) after 1949. The turbocharger hit the automobile world in 1952 when ] qualified for pole position at the ] and led for 100 miles before tire shards disabled the blower.
]'s innovative turbocharged ] ]; The turbo, located at top right, feeds pressurized air into the engine through the chrome T-tube visible spanning the engine from left to right.]]
The first production turbocharged automobile engines came from ]. The ] ] Jetfire and ] Monza Spyder were both fitted with turbochargers in 1962. The Oldsmobile is often recognized as the first, since it came out a few months earlier than the Corvair. Its '']'' was a 215&nbsp;in³ (3.5&nbsp;L) ], while the ] was either a 145&nbsp;in³ (2.3&nbsp;L)(1962-63) or a 164&nbsp;in³ (2.7&nbsp;L) (1964-66) ]. Both of these engines were abandoned within a few years, and GM's next turbo engine came more than ten years later.


== Design ==
]'s turbocharged engines returned to Indianapolis in 1966, with victories coming in 1968. The Offy turbo peaked at over 1,000&nbsp;hp in 1973, while ] dominated the ] series with a 1100&nbsp;hp ]. Turbocharged cars dominated the ] between 1976 and 1988, and then from 2000-2007.


]
] led the resurgence of the automobile turbo with the ] ], with Porsche following with the ], introduced at the ] ]. Buick was the first GM division to bring back the turbo, in the ] ], followed by the ] ] and ] in 1978. The worlds first production turbodiesel automobile was also introduced in 1978 by ] with the launch of the ] turbodiesel. Today, nearly all automotive diesels are turbocharged.


Like other forced induction devices, a ] in the turbocharger pressurises the intake air before it enters the ].<ref>{{cite web|url=http://large.stanford.edu/courses/2010/ph240/veltman1/ |title=Variable-Geometry Turbochargers |publisher=Large.stanford.edu |date=24 October 2010 |access-date=1 June 2012}}</ref> 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 ].<ref>{{cite web |title=Happy 100th Birthday to the Turbocharger - News - Automobile Magazine |url=https://www.motortrend.com/news/turbocharger-history/ |website=www.MotorTrend.com |access-date=25 June 2022 |language=en |date=21 December 2005}}</ref><ref>{{cite web|url=http://conceptengine.tripod.com/conceptengine/id5.html |title=How Turbo Chargers Work |publisher=Conceptengine.tripod.com |access-date=1 June 2012}}</ref>
] introduced the first mass-produced Italian turbocharged car, the Alfetta GTV 2000 Turbodelta in 1979. ] also introduced a turbo in 1980 and ] followed in 1981. ] however gave another step and installed a turbocharger to the smallest and lightest car they had, the ], making it the first ] automobile with a turbocharger in year 1980. This gave the car about 160bhp in street form and up to 300+ in race setup, an exorbitant power for a 1400cc motor. When combined with its incredible lightweight chassis, it could nip at the heels of the quick Italian sports car ].


The main components of the turbocharger are:
In ], in the so called "Turbo Era" of {{F1|1977}} until {{F1|1989}}, engines with a capacity of 1500&nbsp;cc could achieve anywhere from 1000 to 1500&nbsp;hp (746 to 1119&nbsp;kW) (], ], ], ]). Renault was the first manufacturer to apply turbo technology in the F1 field, in 1977. The project's high cost was compensated for by its performance, and led to other engine manufacturers following suit. The Turbo-charged engines took over the F1 field and ended the Ford Cosworth DFV era in the mid 1980s. However, the ] decided that turbos were making the sport too dangerous and expensive, and from {{F1|1987}} onwards, the maximum boost pressure was reduced before the technology was banned completely for {{F1|1989}}.
* Turbine – usually a ] design
* Compressor – usually a ]
* Center housing hub rotating assembly


===Turbine===
In ], turbocharged engines of up to 2000cc have long been the preferred motive power for the Group A/] (top level) competitors, due to the exceptional power-to-weight ratios (and enormous torque) attainable. This combines with the use of vehicles with relatively small bodyshells for manoeuvreability and handling. As turbo outputs rose to similar levels as the F1 category (see above), the ], rather than banning the technology, enforced a restricted turbo inlet diameter (currently 34mm), effectively "starving" the turbo of compressible air and making high boost pressures unfeasible. The success of small, turbocharged, ] vehicles in rally competition, beginning with the ], has led to exceptional road cars in the modern era such as the ], ], ] and the ].
] GT30 with the turbine housing removed]]


The ] 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 ] through the center of a turbo). After the exhaust has spun the turbine it continues into the exhaust piping and out of the vehicle.
In the late 1970s, Ford and GM looked to the turbocharger to gain power, without sacrificing fuel consumption, during not only the emissions crunch of the federal government but also a gas shortage. GM released turbo versions of the Pontiac Firebird, Buick Regal, and Chevy Monte Carlo. Ford responded with a turbocharged Mustang in the form of the 2.3L from the Pinto. The engine design was dated, but it worked well. The bullet-proof 2.3L Turbo was used in early carburated trim as well as fuel injected and intercooled versions in the Mustang SVO and the Thunderbird Turbo Coupe until 1988. GM also liked the idea enough to evolve the 3.8L V6 used in early turbo Buicks into late 80's muscle in the form of the Buick Grand National and the pinical GNX.


The turbine uses a series of blades to convert kinetic energy from 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.<ref>Mechanical engineering: Volume 106, Issues 7-12; p.51</ref><ref>Popular Science. Detroit's big switch to Turbo Power. Apr 1984.</ref> Some turbocharger designs are available with multiple turbine housing options, allowing a housing to be selected to best suit the engine's characteristics and the performance requirements.
Although late to use turbocharging, ] turned to turbochargers in 1984 and quickly churned out more turbocharged engines than any other manufacturer, using turbocharged, fuel-injected 2.2 and 2.5 litre four-cylinder engines in minivans, sedans, convertibles, and coupes. Their 2.2 litre turbocharged engines ranged from 142 hp to 225 hp, a substantial gain over the normally aspirated ratings of 86 to 93 horsepower; the 2.5 litre engines had about 150 horsepower and had no intercooler. Though the company stopped using turbochargers in 1993, they returned to turbocharged engines in 2002 with their 2.4 litre engines, boosting output by 70 horsepower. <ref></ref>


A turbocharger's performance is closely tied to its size,<ref name="eight">{{cite web |last=Veltman |first=Thomas |title=Variable-Geometry Turbochargers |publisher=Coursework for Physics 240 |date=24 October 2010 |url =http://large.stanford.edu/courses/2010/ph240/veltman1/ |access-date=17 April 2012 }}</ref> 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 a limiting factor in the peak power produced by the engine.<ref name="one">{{cite web|last=Tan |first=Paul |title=How does Variable Turbine Geometry work? |publisher=PaulTan.com |date=16 August 2006 |url =http://paultan.org/2006/08/16/how-does-variable-turbine-geometry-work/ |access-date=17 April 2012 }}</ref><ref name="two">A National Maritime Academy Presentation. .</ref> Various technologies, as described in the following sections, are often aimed at combining the benefits of both small turbines and large turbines.
==Design details==
===Stages===
{{expert-subject|Automobiles}}
Turbocharger implementations are often referred to in terms of stages, where a simple turbocharger setup may be denoted Stage I and more advanced developments as Stage II, III etc.
In terms of motorcycle turbochargers, a Stage I system is usually a 'bolt-on' upgrade that requires only minimal alteration to the engine, whereas a later stage may involve increasing injector sizes and fuel pressure regulators, and so on.


Large diesel engines often use a single-stage ] instead of a radial turbine.<ref>{{Citation |last=Schobeiri |first=Meinhard T. |title=Introduction, Turbomachinery, Applications, Types |date=2012 |work=Turbomachinery Flow Physics and Dynamic Performance |pages=3–14 |editor-last=Schobeiri |editor-first=Meinhard T. |url=https://link.springer.com/chapter/10.1007/978-3-642-24675-3_1 |access-date=2024-12-13 |place=Berlin, Heidelberg |publisher=Springer |language=en |doi=10.1007/978-3-642-24675-3_1 |isbn=978-3-642-24675-3}}</ref>
===Components===
]
]
]
]


====Twin-scroll====
The turbocharger has four main components. The ] and ] wheels are each contained within their own folded conical housing on opposite sides of the third component, the center hub rotating assembly (CHRA).
A twin-scroll turbocharger uses two separate exhaust gas inlets, to make use of the pulses in the flow of the exhaust gasses from each cylinder.<ref>{{cite web |title=Twin-Turbocharging: How Does It Work? |url=https://www.carthrottle.com/post/twin-turbocharging-how-does-it-work/ |website=www.CarThrottle.com |date=11 October 2016 |access-date=16 June 2022 |language=en}}</ref> 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 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 ] effect of these gas pulses recovers more energy from the exhaust gases, minimizes parasitic back losses and improves responsiveness at low engine speeds.<ref>{{cite web |title=A Look At Twin Scroll Turbo System Design - Divide And Conquer? |url=https://www.motortrend.com/how-to/modp-0906-twin-scroll-turbo-system-design/ |website=www.MotorTrend.com |access-date=16 June 2022 |language=en |date=20 May 2009}}</ref><ref>{{cite web|last=Pratte |first=David |url=http://www.modified.com/tech/modp-0906-twin-scroll-turbo-system-design/ |title=Twin Scroll Turbo System Design |publisher=Modified Magazine |access-date=28 September 2012}}</ref>


Another common feature of twin-scroll turbochargers 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.<ref>{{cite web |title=BorgWarner's Twin Scroll Turbocharger Delivers Power and Response for Premium Manufacturers - BorgWarner |url=https://www.borgwarner.com/newsroom/press-releases/2020/02/18/borgwarner-s-twin-scroll-turbocharger-delivers-power-and-response-for-premium-manufacturers |website=www.borgwarner.com |access-date=16 June 2022}}</ref>
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. The area of the cone to radius from center hub is expressed as a ratio (AR, A/R, or A:R). Often the same basic turbocharger assembly will be available from the manufacturer with multiple AR choices for the turbine housing 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. Both housings resemble ] shells, and thus turbochargers are sometimes referred to in ] as ''angry snails''.


<gallery heights="150px" mode="packed">
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. Generally, 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.
File:Mitsubishi twin-scroll turbo.JPG |Cutaway view showing the two scrolls of a ] twin-scroll (the larger scroll is illuminated in red)
File:Twin-scroll turbo T-GDI.jpg |Transparent exhaust manifold and turbo scrolls on a ], showing the paired cylinders (1 & 4 and 2 & 3)
</gallery>


====Variable-geometry====
The center hub rotating assembly houses the shaft which 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 ] from the extreme heat found in the turbine.
] variable-geometry turbocharger]]{{Main|Variable-geometry turbocharger}}
Variable-geometry turbochargers (also known as ''variable-nozzle turbochargers'') are used to alter the effective ] of the turbocharger as operating conditions change. This 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 ] to open and close the vanes,<ref>{{cite book|last=Hartman|first=Jeff|title=Turbocharging Performance Handbook|publisher=MotorBooks International|url=https://books.google.com/books?id=SvG0gq4DxecC&pg=PA95|year=2007|isbn=978-1-61059-231-4|page=95}}</ref> while others use a ].


If the turbine's aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio 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.<ref name="eight"/><ref name="one"/> The benefit of variable-geometry turbochargers is that the optimum aspect ratio at low engine speeds is very different from that at high engine speeds.
===Boost===
] refers to the increase in ] that is generated by the turbocharger in the ] path or specifically ] that exceeds normal ]. This is also the level of boost as shown on a ], usually in ], ] or possibly ] This is representative of the extra air pressure that is achieved over what would be achieved without the ]. Manifold pressure should not be confused with the amount, or "weight" of air that a turbo can flow.


==== Electrically-assisted turbochargers ====
Boost pressure is limited to keep the entire engine system including the turbo inside its design operating range by controlling the ] which shunts the exhaust gases away from the exhaust side turbine. In some cars the maximum boost depends on the fuel's ] and is electronically regulated using a ] ], see ] (APC).
An ] combines a traditional exhaust-powered turbine with an electric motor, in order to reduce turbo lag. Recent advancements in electric turbocharger technology,{{when|date=December 2024}} such as mild hybrid integration,<ref>{{Cite web |date=2018-07-04 |title=What is an electric turbocharger? |url=https://www.turbocharger.mtee.eu/what-is-an-electric-turbocharger/ |access-date=2024-12-10 |website=Mitsubishi Turbocharger |language=en-US}}</ref> have enabled turbochargers to start spooling before exhaust gases provide adequate pressure. This can further reduce turbo lag<ref>Truett, Richard, and Jens Meiners. “Electric Turbocharger Eliminates Lag, Valeo Says.” Automotive News, vol. 88, no. 6632, p. 34.</ref> and improve engine efficiency, especially during low-speed driving and frequent stop-and-go conditions seen in urban areas. This differs from an ], which solely uses an electric motor to power the compressor.


=== Compressor ===
Many diesel engines do not have any wastegate because the amount of exhaust energy is controlled directly by the amount of fuel injected into the engine and slight variations in boost pressure do not make a difference for the engine.
] GT30 with the compressor housing removed]]


The ] draws in outside air through the engine's intake system, pressurises it, then feeds it into the ]s (via the ]). 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 ].
===Wastegate===
By spinning at a relatively high speed the compressor turbine draws in a large volume of air and forces it into the engine. As the turbocharger's output flow volume exceeds the engine's volumetric flow, ] in the ] system begins to build, often called ]. The speed at which the assembly spins is proportional to the pressure of the compressed air and total mass of air flow being moved. Since a turbo can spin to RPMs far beyond what is needed, or of what it is safely capable of, the speed must be controlled. A ] is the most common mechanical speed control system, and is often further augmented by an electronic ]. The main function of a wastegate is to allow some of the exhaust to bypass the turbine when the set intake pressure is achieved. Most passenger car wastegates are integral to the turbocharger.


====Ported shroud====
===Anti-Surge/Dump/Blow Off Valves===
Some turbochargers use a "ported shroud", whereby a ring of holes or circular grooves allows air to bleed around the compressor blades. Ported shroud designs can have greater resistance to compressor surge and can improve the efficiency of the compressor wheel.<ref>{{cite web |title=Ported Shroud Conversions |url=https://www.turbodynamics.co.uk/services/turbo-upgrades/ported-shroud-conversion/ |website=www.turbodynamics.co.uk |access-date=18 June 2022}}</ref><ref>{{cite web |title=GTW3684R |url=https://www.garrettmotion.com/racing-and-performance/performance-catalog/turbo/gtw3684r/ |website=www.GarrettMotion.com |access-date=18 June 2022}}</ref>


===Center hub rotating assembly===
Turbo charged 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).
The center hub rotating assembly (CHRA) houses the shaft that connects the turbine to the compressor. A lighter shaft can help reduce turbo lag.<ref>{{cite news|last=Nice |first=Karim |title=How Turbochargers Work |publisher=Auto.howstuffworks.com |url =http://auto.howstuffworks.com/turbo3.htm |access-date=2 August 2010 }}</ref> 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 the engine's coolant to flow through. One reason for water cooling is to protect the turbocharger's lubricating oil from overheating.
This causes a surge which can raise the pressure of the air to a level which can be destructive to the engine e.g. damage may occur to the throttle plate, induction pipes may burst. The surge will also decompress back across the turbo, as this is the only path with the air can take.


== Supporting components ==
The reverse flow back across the turbo acts on the compressor wheel and causes the turbine shaft to reduce in speed quicker than it would naturally. When the throttle is opened again, the turbo will have to spin-up for longer to the required speed, as turbo speed is proportional to boost/volume flow. In order to prevent this from happening, a valve is fitted between the turbo and inlet which vents off the excess volume of air. These are known as anti-surge, dump or blow-off valves. They are normally operated by engine vacuum or by electronic control.
]
The simplest type of turbocharger is the ''free floating'' turbocharger.<ref name="thirteen">{{cite web |title=How Turbocharged Piston Engines Work |publisher=TurboKart.com |url=http://www.turbokart.com/turbochargedengines.htm |access-date=17 April 2012 |archive-date=28 June 2016 |archive-url=https://web.archive.org/web/20160628205047/http://www.turbokart.com/turbochargedengines.htm |url-status=dead }}</ref> 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.<ref name="thirteen"/>


Additional components that are commonly used in conjunction with turbochargers are:
The primary use of this valve is to prevent damage to the engine by a surge of compressed air and to maintain the turbo spinning at a high speed. They can also be used as a bypass valve to control boost in a similar fashion as a waste gate, but this is rarely seen as it is impractical. The air is usually vented to atmosphere, or can be recycled back into the turbo inlet. Recycling back into the turbo causes the venting sound to be reduced but as the excess volume of air is not removed problems may arise.
* ] - a radiator used to cool the intake air after it has been pressurised by the turbocharger<ref>{{cite web |title=How a Turbocharger Works |url=https://www.garrettmotion.com/news/video-center/video/how-a-turbocharger-works |website=www.GarrettMotion.com |access-date=25 June 2022}}</ref>
* ] - spraying water into the combustion chamber, in order to cool the intake air<ref>{{cite web|url=https://www.dragzine.com/tech-stories/engine/get-schooled-water-methanol-injection-101/|title=Get Schooled: Water Methanol Injection 101|first=Mark|last=Gearhart|date=22 July 2011|website=Dragzine}}</ref>
* ] - many turbochargers are capable of producing boost pressures in some circumstances that are higher than the engine can safely withstand, therefore a wastegate is often used to limit the amount of exhaust gases that enters the turbine
* ] - to prevent ''compressor stall'' when the throttle is closed


== Turbo lag and boost threshold {{anchor|Turbocharger lag|Lag}} ==
===Fuel efficiency===
{{refimprove section|date=June 2022}}
Since a turbocharger increases the specific ] output of an engine, the engine will also produce increased amounts of ]. This can sometimes be a problem when fitting a turbocharger to a car that was not designed to cope with high heat loads. This extra waste heat combined with the higher ] (more specifically, expansion ratio) of turbocharged engines contributes to slightly lower ], which has a small but direct impact on overall ] {{Fact|date=June 2007}}.


'''Turbo lag''' refers to delay{{snd}}when the engine rpm is within the turbocharger's operating range{{snd}}that occurs between pressing the throttle and the turbocharger spooling up to provide boost pressure.<ref>{{cite web |title=What Is Turbo Lag? And How Do You Get Rid Of It? |url=https://www.motortrend.com/how-to/what-is-turbo-lag-how-do-you-get-rid-of-it/ |website=www.MotorTrend.com |access-date=12 June 2022 |language=en |date=7 March 2015}}</ref><ref>{{cite web |title=Turbo Lag. Reasons For Turbocharger Lag. How To Fix Turbo Lag |url=https://carbuzz.com/car-advice/what-is-turbo-lag |website=www.CarBuzz.com |access-date=12 June 2022 |language=en-us |date=25 September 2021}}</ref> 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.<ref>{{cite web |title=What is turbo lag? |url=http://www.enginebasics.com/Advanced%20Engine%20Tuning/Turbo%20Lag.html |website=www.enginebasics.com |access-date=12 June 2022}}</ref> The effect of turbo lag is reduced ], in the form of a delay in the power delivery.<ref>{{cite web |title=5 Ways To Reduce Turbo Lag |url=https://www.carthrottle.com/post/how-can-you-reduce-turbo-lag/ |website=www.CarThrottle.com |date=19 July 2016 |access-date=12 June 2022 |language=en}}</ref> Superchargers do not suffer from turbo lag because the compressor mechanism is driven directly by the engine.
It is another form of cooling that has the largest impact on fuel efficiency: charge cooling. Even with the benefits of ], the total compression in the ] is greater than that in a ]. To avoid ] while still extracting maximum power from the engine, it is common practice to introduce extra fuel into the charge for the sole purpose of cooling. While this seems counterintuitive, this fuel is not burned. Instead, it absorbs and carries away heat when it changes phase from liquid mist to gas vapor. Also, because it is more dense than the other inert substance in the combustion chamber, ], it has a higher specific heat and more heat capacitance. It "holds" this heat until it is released in the ] stream, preventing destructive ]. This thermodynamic property allows manufacturers to achieve good power output with common pump fuel at the expense of fuel economy and emissions. The ] Air-to-Fuel ratio (A/F) for combustion of gasoline is 14.7:1. A common A/F in a turbocharged engine while under full design boost is approximately 12:1. Richer mixtures are sometimes run when the design of the system has flaws in it such as a catalytic converter which has limited endurance of high exhaust temperatures or the engine has a compression ratio that is too high for efficient operation with the fuel given.


Methods to reduce turbo lag include:{{citation needed|date=June 2022}}
Lastly, the efficiency of the turbocharger itself can have an impact on fuel efficiency. Using a small turbocharger will give quick response and low lag at low to mid RPMs, but can choke the engine on the exhaust side and generate huge amounts of pumping-related heat on the intake side as RPMs rise. A large turbocharger will be very efficient at high RPMs, but is not a realistic application for a street driven automobile. Variable vane and ball bearing technologies can make a turbo more efficient across a wider operating range, however, other problems have prevented this technology from appearing in more road cars (see ]). Currently, the ] is the only gasoline car in production with this kind of turbocharger. One way to take advantage of the different operating regimes of the two types of supercharger is ], which uses a small turbocharger at low RPMs and a larger one at high RPMs.
* Lowering the rotational inertia of the turbocharger by using lower radius parts and ceramic and other lighter materials
* Changing the turbine's ''] (A/R ratio)''
* Increasing upper-deck air pressure (compressor discharge) and improving wastegate response
* Reducing bearing frictional losses, e.g., using a ] rather than a conventional oil bearing
* Using ] or ] turbochargers
* Decreasing the volume of the upper-deck piping
* Using multiple turbochargers sequentially or in parallel
* Using an ]
* Using a turbocharger spool valve to increase exhaust gas flow speed to the (twin-scroll) turbine
* Using a ] to force exhaust gas through a smaller passage in the turbo inlet
* Electric turbochargers<ref name=parkhurst>{{cite web|last=Parkhurst |first=Terry |title=Turbochargers: an interview with Garrett's Martin Verschoor |date=10 November 2006 |publisher=Allpar |url =http://www.acarplace.com/cars/turbochargers.html |access-date=12 December 2006}}</ref> and ]s.


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 is unable to produce significant boost. At low rpm, the exhaust gas flow rate is unable to spin the turbine sufficiently.
The engine management systems of most modern vehicles can control ] and fuel delivery according to charge temperature, fuel quality, and altitude, among other factors. Some systems are more sophisticated and aim to deliver fuel even more precisely based on combustion quality. For example, the Trionic-7 system from ] provides immediate feedback on the combustion while it is occurring using an electrical charge.


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.
The new 2.0L ] turbo engine from ]/] incorporates lean burn and direct injection technology to conserve fuel under low load conditions. It is a very complex system that involves many moving parts and sensors in order to manage airflow characteristics inside the chamber itself, allowing it to use a stratified charge with excellent atomization. The direct injection also has a tremendous charge cooling effect enabling engines to use higher compression ratios and boost pressures than a typical port-injection turbo engine.


== Use of multiple turbochargers ==
===Automotive design details===
{{main|Twin-turbo}}
The ] states that when all other variables are held constant, if pressure is increased in a system so will temperature. Here exists one of the negative consequences of turbocharging, the increase in the temperature of air entering the engine due to compression.


Some engines use multiple turbochargers, usually to reduce turbo lag, increase 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.
A turbo spins very fast; most peak between 80,000 and 200,000&nbsp;RPM (using low ] turbos, 150,000-250,000&nbsp;RPM) depending on size, weight of the rotating parts, boost pressure developed and compressor design. Such high rotation speeds would cause problems for standard ]s leading to failure so most turbo-chargers use ]s. These feature a flowing layer of oil that suspends and cools the moving parts. The oil is usually taken from the engine-oil circuit. Some turbochargers use incredibly precise ball bearings that offer less friction than a fluid bearing but these are also suspended in fluid-dampened cavities. Lower friction means the turbo shaft can be made of lighter materials, reducing so-called ''turbo lag'' or ''boost lag''. Some car makers use water cooled turbochargers for added bearing life. This can also account for why many tuners upgrade their standard journal bearing turbos (such as a T25) which use a 270 degree thrust bearing and a brass journal bearing which only has 3 oil passages, to a 360 degree bearing which has a beefier thrust bearing and washer having 6 oil passages to enable better flow, response and cooling efficiency.
Turbochargers with ]s are in development which eliminates the need for bearing cooling or oil delivery systems, thereby eliminating the most common cause of failure, while also significantly reducing turbo lag.


==Turbocharging versus supercharging==
To manage the ''upper-deck'' air pressure, the turbocharger's exhaust gas flow is regulated with a ] that bypasses excess exhaust gas entering the turbocharger's turbine. This regulates the rotational speed of the turbine and the output of the compressor. The wastegate is opened and closed by the compressed air from turbo (the upper-deck pressure) and can be raised by using a ] to regulate the pressure fed to the wastegate membrane. This solenoid can be controlled by ], the engine's ] or an after market boost control computer. Another method of raising the boost pressure is through the use of check and bleed valves to keep the pressure at the membrane lower than the pressure within the system.
{{main|Supercharger#Supercharging versus turbocharging{{!}} Supercharger #Supercharging versus turbocharging}}
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 the ]) whereas a turbocharger is powered by the kinetic energy of the engine's ].<ref name="auto.howstuffworks.com">{{cite web |url=http://auto.howstuffworks.com/question122.htm |title=What is the difference between a turbocharger and a supercharger on a car's engine? |website=HowStuffWorks |date=1 April 2000 |access-date=1 June 2012}}</ref> A turbocharger does not place a direct mechanical load on the engine, although turbochargers place exhaust back pressure on engines, increasing pumping losses.<ref name="auto.howstuffworks.com"/>


Supercharged engines are common in applications where throttle response is a key concern, and supercharged engines are less likely to ] the intake air.
Some turbochargers (normally called ]s) utilize 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. These turbochargers have minimal amount of lag, have a low boost threshold (with full boost as low as 1,500 rpm), and are efficient at higher engine speeds; they are also used in diesel engines. <ref>{{cite web
| last = Parkhurst
| first =Terry
| title = Turbochargers: an interview with Garrett’s Martin Verschoor
| publisher = Allpar, LLC
| url =http://www.acarplace.com/cars/turbochargers.html
| accessdate = ] ]}}</ref> In many setups these turbos don't even need a wastegate. The vanes are controlled by a membrane identical to the one on a wastegate but the level of control required is a bit different.


=== Twincharging ===
The first production car to use these turbos was the limited-production ] ], in essence a ] equipped with a 2.2L ]. The Shelby CSX-VNT utilized a turbo from ], called the VNT-25 because it uses the same compressor and shaft as the more common Garrett T-25. This type of turbine is called a '''Variable Nozzle Turbine (VNT)'''. Turbocharger manufacturer Aerocharger uses the term 'Variable Area Turbine Nozzle' (VATN) to describe this type of turbine nozzle. Other common terms include Variable Turbine Geometry (VTG), Variable Geometry Turbo (VGT) and Variable Vane Turbine (VVT). A number of other ] vehicles used this turbocharger in 1990, including the ] and ]. These engines produced 174 horsepower and 225 pound-feet of torque, the same horsepower as the standard intercooled 2.2 liter engines but with 25 more pound-feet of torque and a faster onset (less turbo lag). However, the Turbo III engine, without a VATN or VNT, produced 224 horsepower. The reasons for Chrysler's not continuing to use variable geometry turbochargers are unknown, but the main reason was probably public desire for V6 engines coupled with increased availability of Chrysler-engineered V6 engines. <ref></ref>
{{main|Twincharger}}
A combination of an exhaust-driven turbocharger and an engine-driven supercharger can mitigate the weaknesses of both.<ref>{{cite web |url=http://www.torquecars.com/tuning/twincharging.php |title=How to twincharge an engine |date=29 March 2012 |publisher=Torquecars.com |access-date=1 June 2012}}</ref> This technique is called ''twincharging''.


== Applications ==
The 2006 ] has a twin turbocharged 3.6-litre flat six, and the turbos used are ]'s Variable Geometry Turbos (VGTs). This is significant because although VGTs have been used on advanced diesel engines for a few years and on the Shelby CSX-VNT, this is the first time the technology has been implemented on a production petrol car since the 1,250 Dodge engines were produced in 1989-90. Some have argued this is because in petrol cars exhaust temperatures are much higher (than in diesel cars), and this can have adverse effects on the delicate, moveable vanes of the turbocharger; these units are also more expensive than conventional turbochargers. Porsche engineers claim to have managed this problem with the new 911 Turbo.
]
Turbochargers have been used in the following applications:
* ]
* ]
* ] (quite rarely)
* Diesel-powered ], beginning with a ] truck in 1938<ref>{{cite web|url=http://www.turbodriven.com/en/turbofacts/default.aspx |title=BorgWarner turbo history |publisher=Turbodriven.com |access-date=2 August 2010}}</ref>
* ] and ] diesel engines
* ]
* ]s
* ] and ] engines for trains
* ]


In 2017, 27% of vehicles sold in the US were turbocharged.<ref>{{cite web |url=https://www.wardsauto.com/engines/turbo-engine-use-record-high |title=Turbo Engine Use at Record High |work=Wards Auto |date=7 August 2017 |access-date=22 July 2021 }}</ref> In Europe 67% of all vehicles were turbocharged in 2014.<ref>{{cite web|title=Honeywell sees hot turbo growth ahead|url=http://www.autonews.com/article/20150112/OEM10/301129998/honeywell-sees-hot-turbo-growth-ahead|website=Automotive News|date=7 January 2015 |access-date=19 May 2017|ref=autonewshoneywell}}</ref> Historically, more than 90% of turbochargers were diesel, however, adoption in petrol engines is increasing.<ref name="thirty">{{cite news|last=Kahl |first=Martin |title=Interview: David Paja, VP, Global Marketing and Craig Balis, VP, Engineering Honeywell Turbo |publisher=Automotive World |date=3 November 2010 |url =http://honeywellbooster.com/assets/interview-honeywell-david-paja-craig-balis.pdf |access-date=11 November 2011 }}</ref> The companies which manufacture the most turbochargers in Europe and the U.S. are ] (formerly Honeywell), ] and ].<ref name="reviews.cnet.com"/><ref name="bloomberg.com">{{cite web|last=Kitamura |first=Makiko |url=https://www.bloomberg.com/apps/news?pid=newsarchive&sid=aYKNPOS_J37k |title=IHI Aims to Double Turbocharger Sales by 2013 on Europe Demand |publisher=Bloomberg |date=24 July 2008 |access-date=1 June 2012}}</ref><ref name="just-auto.com">{{cite web|author=CLEPA CEO Lars Holmqvist is retiring |url=http://www.just-auto.com/analysis/turbochargers-european-growth-driven-by-spread-to-small-cars_id86995.aspx |title=Turbochargers - European growth driven by spread to small cars |publisher=Just-auto.com |date=18 November 2002 |access-date=1 June 2012}}</ref>
=== Motorcycles===


==Safety==
Using turbochargers to gain performance without a large gain in weight was very appealing to the Japanese factories in the 1980s. ], ] and ] chose the route of an inline four with a turbo unit. However ] uprated their CX500 Vee twin along with an upgraded chassis and an added fairing and so produced their flagship performance model. It raised the standard machines power from 50BHP to 82BHP at 8,000rpm, using a maximum boost of 18.5psi. It was no faster than the current 750's of the day and weighed a not inconsiderable 574lb (curb weight). ] was a problem with this machine, its performance in town and urban riding with its low compression ratio and when off boost was underwhelming. Fuel injection, watercooling, and a 2 inch turbo spinning to 200,000 rpm was not enough to impress the buying public. Honda's Hi-tec approach and even a capacity lift to 650cc was not enough to reverse the trend. The other Japanese factories fared little better, though of all the 'fours' Kawasaki's ] was perhaps the best.
Turbocharger failures and resultant high exhaust temperatures are among the causes of car fires.<ref>. Australian Road Transport Suppliers Association (ARTSA). November 2006. Retrieved 2020-07-22.</ref>
It looked much like its non boosted version (86 BHP) and still aircooled, but put out 112 BHP, putting it into the performance range (if not handling) of its stablemate GPZ900 (Ninja).
The Suzuki's Turbo was the XN85 (its quoted BHP) this extracted from only 650cc. It had something of its ] relatives looks, 16inch front wheel and monoshock rear suspension, but was soon overshadowed by the release of Suzukis own GS750ES later in 1983, it was only in production until 1986.
Yamaha stayed with a carburetter for their turbo model, the standard engine put out 73BHP the XJ650Turbo however put out 90BHP at 8,500rpm, and was released at the 1981 Tokyo Motorcycle Show.


Failure of the seals will cause oil to leak into the cylinders causing blue-gray smoke. In diesel engines, this can cause an overspeed, a condition known as ].
==Properties and Applications==
===Reliability===
Turbochargers can be damaged by dirty or ineffective oil, and most manufacturers recommend more frequent oil changes for turbocharged engines; many owners and some companies recommend using ]s, which tend to flow more readily when cold and do not break down as quickly as conventional oils. Because the turbocharger can get hot when running, many recommend letting the engine idle for one to three minutes before shutting off the engine if the turbocharger was used shortly before stopping (most manufacturers specify a 10-second period of idling before switching off to ensure the turbocharger is running at its idle speed to prevent damage to the bearings when the oil supply is cut off). This lets the turbo rotating assembly cool from the lower exhaust gas temperatures, and ensures that oil is supplied to the turbocharger while the turbine housing and exhaust manifold are still very hot; otherwise ]<!-- yes, this is the correct spelling--> 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 ]s, due to the lower exhaust temperatures and generally slower engine speeds.


==See also==
A ] can keep an engine running for a pre-specified period of time, to automatically provide this cool-down period. Oil coking <!-- yes, this is the correct spelling--> is also eliminated by ]. A more complex and problematic protective barrier against oil coking <!-- yes, this is the correct spelling--> is the use of watercooled bearing cartridges. The water boils in the cartridge when the engine is shut off and forms a natural recirculation to drain away the heat. It is still a good idea to not shut the engine off while the turbo and manifold are still glowing.
{{Commons category|Turbochargers}}

* ]
In custom applications utilizing tubular headers rather than ] manifolds, the need for a cooldown period is reduced because the lighter headers store much less heat than heavy cast iron manifolds.
* ]

* ]
===Lag===<!-- This section is linked from ] -->
* ]
] engine (] from a ]) in a ].]]
A ] is sometimes felt by the driver of a turbocharged vehicle as a delay between pushing on the accelerator pedal and feeling the turbo ''kick-in''. This is symptomatic of the time taken for the exhaust system driving the turbine to come to high pressure and for the turbine rotor to overcome its ] and reach the speed necessary to supply boost pressure. The directly-driven compressor in a ] does not suffer this problem. (Centrifugal superchargers do not build boost at low RPMs like a positive displacement supercharger will). Conversely on light loads or at low RPM a turbocharger supplies less boost and the engine is more efficient than a supercharged engine.

Lag can be reduced by lowering the rotational inertia of the turbine, for example by using lighter parts to allow the spool-up to happen more quickly. Ceramic turbines are a big help in this direction. Unfortunately, their relative fragility limits the maximum boost they can supply. Another way to reduce lag is to change the ] of the turbine by reducing the diameter and increasing the gas-flow path-length. Increasing the upper-deck air pressure and improving the ] response helps but there are cost increases and reliability disadvantages that car manufacturers are not happy about. Lag is also reduced by using a ] rather than a conventional oil bearing. This reduces friction and contributes to faster acceleration of the turbo's rotating assembly. Variable-nozzle turbochargers (discussed above) also reduce lag.

Another common method of equalizing turbo lag is to have the turbine wheel "clipped", or to reduce the surface area of the turbine wheel's rotating blades. By clipping a minute portion off the tip of each blade of the turbine wheel, less restriction is imposed upon the escaping exhaust gases. This imparts less impedance onto the flow of exhaust gases at low RPM, allowing the vehicle to retain more of its low-end ], but also pushes the effective boost RPM to a slightly higher level. The amount a turbine wheel is and can be clipped is highly application-specific. Turbine clipping is measured and specified in degrees.

Other setups, most notably in ]s, 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, faster. Such an arrangement of turbos is typically referred to as a ] system.

Some car makers combat lag by using two small turbos (such as ], ], ], ], ], and ]). 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. Early designs would have one turbocharger active up to a certain RPM, after which both turbochargers are active. 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-turbos are usually much more complicated than a single or parallel twin-turbo systems because they require what amounts to three sets of pipes-intake and wastegate pipes for the two turbochargers as well as valves to control the direction of the exhaust gases. An example of this is the current ] ] 535d. Another well-known example is the 1993-2002 Mazda RX-7. Many new diesel engines use this technology to not only eliminate lag but also to reduce fuel consumption and produce cleaner emissions.

Lag is not to be confused with the boost threshold; however, many publications still make this basic mistake. The boost threshold of a turbo system describes the minimum engine RPM at which there is sufficient exhaust flow to the turbo to allow it to generate significant amounts of boost{{Fact|date=February 2007}}. Newer turbocharger and engine developments have caused boost thresholds to steadily decline to where day-to-day use feels perfectly natural. Putting your foot down at 1200 engine RPM and having no boost until 2000 engine RPM is an example of boost threshold and not ''lag''. If lag was experienced in this situation, the RPM would either not start to rise for a short period of time after the thottle was increased, or increase slowly for a few seconds and then suddenly build up at a greater rate as the turbo become effective. Howewer, the term lag is used for boost threshold by many manufacturers themselves so as not to confuse common man with many words.

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. The electric motor is about an inch long. <ref>{{cite web
| last = Parkhurst
| first =Terry
| title = Turbochargers: an interview with Garrett’s Martin Verschoor
| publisher = Allpar, LLC
| url =http://www.acarplace.com/cars/turbochargers.html
| accessdate = 12/12/2006}}</ref>

] often utilize an ] to completely eliminate lag at the cost of reduced turbocharger life.

On modern ]s, this problem is virtually eliminated by utilizing a ].

===Boost Threshold===
Turbocharger starts producing boost only above a certain rpm (depending on the size of the turbo) due to a lack of exhaust gas volume to overcome the ] of the turbo propeller {{Fact|date=June 2007}}. Power suddenly increases after that particular rpm when turbo propeller starts spinning. So power Vs rpm curve of a turbocharged engine has a steep increase in power at boost threshold rpm. There have been many advancements in technology to reduce boost threshold rpm below idle speed rpm of the engine, so as to virtually eliminate the boost threshold.

===Automotive Applications===
Turbocharging is very common on ]s in conventional automobiles, in ]s, ], for marine and heavy machinery applications. In fact, for current automotive applications, non-turbocharged diesel engines are becoming increasingly rare. Diesels are particularly suitable for turbocharging for several reasons:
* ] diesels will develop less power than a gasoline engine of the same size, and will weigh significantly more because diesel engines require heavier, stronger components. This gives such engines a poor ]; turbocharging can dramatically improve this P:W ratio, with large power gains for a very small (if any) increase in weight.
* Diesel engines require more robust construction because they already run at very high ] and at high temperatures so they generally require little additional reinforcement to be able to cope with the addition of the turbocharger. Gasoline engines often require extensive modification for turbocharging.
* Diesel engines have a narrower band of engine speeds at which they operate, thus making the operating characteristics of the turbocharger over that "rev range" less of a compromise than on a gasoline-powered engine.
* Diesel engines blow nothing but air into the cylinders during cylinder charging, squirting fuel into the cylinder only after the intake valve has closed and compression has begun. Gasoline/petrol engines differ from this in that both fuel and air are introduced during the intake cycle and both are compressed during the compression cycle. The higher intake charge temperatures of forced-induction engines reduces the amount of compression that is possible with a gasoline/petrol engine, whereas diesel engines are far less sensitive to this.

Today, turbocharging is most commonly used on two types of engines: 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 larger-output (and physically larger) engine. ] is a leader in production car turbochargers, starting with the ] ]; all current Saab models are turbocharged with the exception of the ]. The ] utilized a turbo unit in the 944 Turbo (Porsche internal model number 951), to great advantage, bringing its 0-100&nbsp;km/h (0-60&nbsp;mph) times very close to its contemporary non-turbo "big brother", the ].

In the 1980s, when turbocharged production cars became common, they gained a reputation for being difficult to handle. The tuned engines fitted to the cars, and the often primitive turbocharger technology meant that power delivery was unpredictable and the engine often suddenly delivered a huge boost in power at certain speeds. Some drivers said this made cars such as the ] and the ] exciting to drive, requiring high levels of skill. Others said the cars were difficult and often dangerous. As turbocharger technology improved, it became possible to produce turbocharged engines with a smoother, more predictable but just as effective power delivery.

] was an innovator of turbocharger use in the ]. Many of their production vehicles, for example the ], ], ]/] twins, and the ]/] twins were available with turbochargers, and they proved very popular with the public. They are still considered competitive vehicles today, and the experience Chrysler obtained in observing turbochargers in real-world conditions has allowed them to further turbocharger technology with the ] Turbo, the ] and the ] SRT-4.

is a form of turbocharger that generates electricity instead of boosting engine's air flow. On ] ], announced the first known implementation of such unit for automobiles, under the name (Turbo-generator Integrated Gas Energy Recovery System).

===Aircraft Applications===
Turbochargers are used in reciprocating aircraft engines which are designed for high altitude use. As an aircraft climbs in altitude, the density of the air surrounding it decreases. As the density of the air decreases, so does the drag on the airframe, but so does the power of the engine. With this in mind, turbochargers were developed for aircraft to keep the pressure of the air entering the engine equivalent to a normally aspirated engine at sea level. In this case the system is called a ''turbo-normalizer''. Other systems use the turbocharger to boost the engine manifold pressure to much higher than sea level pressures; in the area of 35 to 45 ]; and this is called ''turbo-boosting''. In either case, an automatic or manually-controlled ] is used to vary the turbocharger output according to operating conditions.

===Implementations===
The most common implemenations of a turbocharger involve mounting the unit to the downpipe of a vehicle under the hood towards the firewall of the vehicle.

A rear mount implementation is used when there is insufficient engine bay room; it may be used in place of the stock muffler. The turbo returns the boosted air (which is pulled in from a filter mounted somewhere in the rear) to the front of the vehicle and optionally through an intercooler, and then to the intake of the engine. Wiring and oil lines must be run to the rear of the vehicle and an auxiliary oil pump must be used to return oil from the turbo to the engine. According to Horsepower TV (2/3/2007), you can expect a loss of 1 psi using a rear mount turbo, because of loss due to the long pipe routings, and also about a 100°F drop in intake air temperature. The decrease is due to the cooler exhaust gases (thus a cooler turbo unit) and the cooler intermediate pipe between the turbo and the intake. Benefits include easier maintenance, because the unit is more accessible.

==Relationship to Gas Turbine Engines==
Prior to World War II, ] started his experiments on early ] engines. Due to a lack of sufficient materials as well as funding, initial progress was slow. However, turbochargers were used extensively in military aircraft during World War II to enable them to fly very fast at very high altitudes. The demands of the war led to constant advances in turbocharger technology, particularly in the area of materials. This area of study eventually crossed over in to the development of early ]. Those early turbine engines were little more than a very large turbocharger with the compressor and turbine connected by a number of ]. Consider also, for example, that ] manufactured turbochargers for military aircraft and held several patents on their electric turbo controls during the war, then used that expertise to very quickly carve out a dominant share of the gas turbine market which they have held ever since. Other companies such as ] make both gas turbine engines and turbochargers.

== Advantages and Disadvantages ==
=== Advantages ===
* More specific power over naturally aspirated engine. This means a turbocharged engine can achieve more power from same engine volume.
* Better thermal efficiency over both naturally aspirated and supercharged engine when under full load (i.e. on boost). This is because the excess exhaust heat and pressure, which would normally be wasted, contributes some of the work required to compress the air.
* Weight/Packaging. Smaller and lighter than alternative forced induction systems and may be more easily fitted in an engine bay.

===Disadvantages===
* Lack of responsiveness if an incorrectly sized turbocharger is used. If a turbocharger that is too large is used it reduces throttle response as it builds up boost slowly. However, doing this may result in more ''peak'' power.
* Boost threshold. Turbocharger starts producing boost only above a certain rpm due to a lack of exhaust gas volume to overcome ] of turbo propeller. This results in low torque at low revs, and hence reduces the usable power band of the engine. Also may result in sudden oversteer of ] cars during cornering {{Fact|date=June 2007}}.
* Cost. Turbocharger parts are costly to add to naturally aspirated engines.
* Complexity. Further to cost, turbochargers require numerous additional systems if they are not to damage an engine. Even an engine under only light boost requires a system for cooling the lubricating oil and upgraded piston crowns, exhaust valves and valve seats. ] turbo engines require additional plumbing, whilst highly tuned turbocharged engines will require extensive upgrades to their lubrication, cooling and breathing systems.
* Lag can be disadvantageous in racing. If throttle is applied in a turn, power may unexpectedly increase when the turbo winds up, which can induce oversteer.


==References== ==References==
{{Reflist|35em}}
* {{cite journal
| url=http://www.automobilemag.com/features/news/0602_turbocharger_history/index.html
| |title=Happy 100th Birthday to the Turbocharger
| |author=Don Sherman
| journal=]
| date=February 2006
}}
<references/>

== See also ==
*]
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*]
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== External links ==
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Latest revision as of 08:10, 2 January 2025

Exhaust-powered forced-induction device for engines

"turbo" redirects here. For other uses, see turbo (disambiguation).
Cut-away view turbocharger (turbine section on the left, compressor section on the right)

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 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.

History

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 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 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 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 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 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 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 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 the 1980s, as a way to increase the performance of smaller displacement engines.

Design

Turbocharger components

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 the turbocharger are:

Turbine

Turbine section of a Garrett GT30 with the turbine housing removed

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 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 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 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.

Twin-scroll

A twin-scroll turbocharger uses two separate exhaust gas inlets, to make use of the pulses in 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 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 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.

  • Cutaway view showing the two scrolls of a Mitsubishi twin-scroll (the larger scroll is illuminated in red) Cutaway view showing the two scrolls of a Mitsubishi twin-scroll (the larger scroll is illuminated in red)
  • Transparent exhaust manifold and turbo scrolls on a Hyundai Gamma engine, showing the paired cylinders (1 & 4 and 2 & 3) Transparent exhaust manifold and turbo scrolls on a Hyundai Gamma engine, showing the paired cylinders (1 & 4 and 2 & 3)

Variable-geometry

Cutaway view of a Porsche variable-geometry turbocharger
Main article: Variable-geometry turbocharger

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 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 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 is that the optimum aspect ratio at low engine speeds is very different from that at high engine speeds.

Electrically-assisted turbochargers

An electrically-assisted turbocharger combines a traditional exhaust-powered turbine with an electric motor, in order to reduce turbo lag. Recent advancements in electric turbocharger technology, such as mild hybrid integration, have enabled turbochargers to start spooling before exhaust gases provide adequate pressure. This can further reduce turbo lag and improve engine efficiency, especially during low-speed driving and frequent stop-and-go conditions seen in urban areas. This differs from an electric supercharger, which solely uses an electric motor to power the compressor.

Compressor

Compressor section of a Garrett GT30 with the compressor housing removed

The compressor draws in outside air through 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.

Ported shroud

Some turbochargers use a "ported shroud", whereby a ring of holes or circular grooves allows air to bleed around the compressor blades. Ported shroud designs can have greater resistance to compressor surge and can improve the efficiency of the compressor wheel.

Center hub rotating assembly

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 the engine's coolant to flow through. One reason for water cooling is to protect the turbocharger's lubricating oil from overheating.

Supporting components

Schematic of a typical turbo petrol engine

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:

  • Intercooler - a radiator used to cool the intake air after it has been pressurised by the turbocharger
  • Water injection - spraying water into the combustion chamber, in order to cool the intake air
  • Wastegate - many turbochargers are capable of producing boost pressures in some circumstances that are higher than the engine can safely withstand, therefore a wastegate is often used to limit the amount of exhaust gases that enters the turbine
  • Blowoff valve - to prevent compressor stall when the throttle is closed

Turbo lag and boost threshold

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Turbo lag refers to delay – when 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 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:

  • Lowering the rotational inertia of the turbocharger by using lower radius parts and ceramic and other lighter materials
  • Changing the turbine's aspect ratio (A/R ratio)
  • Increasing upper-deck air pressure (compressor discharge) and improving wastegate response
  • Reducing bearing frictional losses, e.g., using a foil bearing rather than a conventional oil bearing
  • Using variable-nozzle or twin-scroll turbochargers
  • Decreasing the volume of the upper-deck piping
  • Using multiple turbochargers sequentially or in parallel
  • Using an antilag system
  • Using a turbocharger spool valve to increase exhaust gas flow speed to the (twin-scroll) turbine
  • Using a butterfly valve to force exhaust gas through a smaller passage in the turbo inlet
  • Electric turbochargers and hybrid turbochargers.

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 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.

Use of multiple turbochargers

Main article: Twin-turbo

Some engines use multiple turbochargers, usually to reduce turbo lag, increase 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.

Turbocharging versus supercharging

Main article: Supercharger #Supercharging versus turbocharging

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 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 the intake air.

Twincharging

Main article: Twincharger

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

Applications

A medium-sized six-cylinder marine diesel-engine, with turbocharger and exhaust in the foreground

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 is increasing. The companies which manufacture the most turbochargers in Europe and the U.S. are Garrett Motion (formerly Honeywell), BorgWarner and Mitsubishi Turbocharger.

Safety

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, a condition known as diesel engine runaway.

See also

References

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  9. Vann, Peter (11 July 2004). Porsche Turbo: The Full History. MotorBooks International. ISBN 9780760319239.
  10. ^ Miller, Jay K. (2008). Turbo: Real World High-Performance Turbocharger Systems. CarTech Inc. p. 9. ISBN 9781932494297. Retrieved 20 September 2019.
  11. DE 204630  "Verbrennungskraftmaschinenanlage"
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  17. Compressor Performance: Aerodynamics for the User. M. Theodore Gresh. Newnes, 29 March 2001
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  22. US 4838234  Mayer, Andreas: "Free-running pressure wave supercharger", issued 1989-07-13, assigned to BBC Brown Boveri AG, Baden, Switzerland
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  28. Mechanical engineering: Volume 106, Issues 7-12; p.51
  29. Popular Science. Detroit's big switch to Turbo Power. Apr 1984.
  30. ^ Veltman, Thomas (24 October 2010). "Variable-Geometry Turbochargers". Coursework for Physics 240. Retrieved 17 April 2012.
  31. ^ Tan, Paul (16 August 2006). "How does Variable Turbine Geometry work?". PaulTan.com. Retrieved 17 April 2012.
  32. A National Maritime Academy Presentation. Variable Turbine Geometry.
  33. Schobeiri, Meinhard T. (2012), Schobeiri, Meinhard T. (ed.), "Introduction, Turbomachinery, Applications, Types", Turbomachinery Flow Physics and Dynamic Performance, Berlin, Heidelberg: Springer, pp. 3–14, doi:10.1007/978-3-642-24675-3_1, ISBN 978-3-642-24675-3, retrieved 13 December 2024
  34. "Twin-Turbocharging: How Does It Work?". www.CarThrottle.com. 11 October 2016. Retrieved 16 June 2022.
  35. "A Look At Twin Scroll Turbo System Design - Divide And Conquer?". www.MotorTrend.com. 20 May 2009. Retrieved 16 June 2022.
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