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{{Short description|Exhaust-powered forced-induction device for engines}}
{{redirect|Turbo}}
{{Redirect|Turbo}}
[[Image:Turbocharger.jpg|right|thumb|350px|Air [[foil bearing]]-supported turbocharger cutaway made by [http://mohawkinnovative.com/newsletters/06_oilfree_turbocharger_gas_engine_applications.pdf Mohawk Innovative Technology Inc.] ]]
{{Use dmy dates|date=October 2019}}
[[File:Turbocharger Animation by Tyroola.gif|thumb|upright=1.35|A turbocharger (item 10) on a piston engine]]
 
In an [[internal combustion engine]], a '''turbocharger''' (also known as a '''turbo''' or a '''turbosupercharger''') is a [[forced induction]] device that compresses the intake air, forcing more air into the engine in order to produce more power for a given [[engine displacement|displacement]].<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">[http://reviews.cnet.com/8301-13746_7-20045466-48.html] {{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''' is an exhaust gas-driven [[Gas compressor|compressor]] used to increase the power output of an [[internal-combustion engine]] by compressing air that is entering the engine thus increasing the amount of available [[oxygen]]. A key advantage of turbochargers is that they offer a considerable increase in engine power with only a slight increase in weight.
 
Turbochargers are distinguished from [[supercharger]]s in 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.<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>
==Principle of operation==
 
== History ==
A turbocharger is a [[Gas compressor|dynamic compressor]], in which air or gas is compressed by the mechanical action of [[impeller]]s, vaned [[rotor]]s which are spun using the kinetic movement of air, imparting [[velocity]] and [[pressure]] to the flowing medium.
 
Prior to the invention of the turbocharger, [[forced induction]] was only possible using mechanically-powered [[supercharger]]s. Use of superchargers began in 1878, when several supercharged two-stroke gas engines were built using a design by Scottish engineer [[Dugald Clerk]].<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, [[Gottlieb Daimler]] 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 mechanical concept of a turbocharger revolves around three main parts. A [[turbine]] is driven by the exhaust gas from a [[pump]], most often an [[internal combustion engine]], to spin the second main part, an [[impeller]] whose function is to force more air into the pump's intake, or air supply. The third basic part is a center hub rotating assembly (CHRA) which contains [[Bearing (mechanical)|bearing]], [[lubrication]], cooling, and a shaft that directly connects the turbine and impeller. The shaft, bearing, impeller, and turbine can rotate at speeds in the tens or hundreds of thousands of RPM ([[revolutions per minute]]).
 
The 1905 patent by [[Alfred Büchi]], a Swiss engineer working at [[Sulzer (manufacturer)|Sulzer]] 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 [[radial engine]] with an exhaust-driven axial flow [[turbine]] 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=usurped |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 |archive-date=29 March 2020 |archive-url=https://web.archive.org/web/20200329084913/http://www.cummins.ru/en/components/turbo-technologies/turbocharger-history |url-status=dead }}</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 [[Auguste Rateau]], 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 [[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 {{convert|4250|m|ft|0|abbr=on}} above sea level.<ref name="Miller"/> The testing was conducted at [[Pikes Peak]] in the United States using the [[Liberty L-12]] aircraft engine.<ref name="Air & Space, Hill Climb" />
The lubrication system can be either a closed system or be fed from the engine's oil supply. The lubrication system may double as the cooling system, or separate coolant may be pumped through the center housing from an outside source. An oil lubrication and water cooling system using engine oil and engine coolant are commonplace in automotive applications.
[[Image:Twinturbo.JPG|thumb|250px|right|A Pair of turbochargers mounted to an [[Inline 6]] engine in a [[dragster]].]]
The [[turbine]] and [[impeller]] are each contained within their own folded conical housing on opposite sides of the center hub rotating assembly. These housings collect and direct the gas flow. 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 [[snail]] shells, and thus turbochargers are sometimes referred to in [[slang]] as ''snails''.
 
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.<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 |url-status=usurped |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" />
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, [[manifold absolute pressure|air pressure]] in the [[intake]] system begins to build, often called [[Boost (automotive engineering)|boost]]. 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 [[wastegate]] is the most common mechanical speed control system, and is often further augmented by an electronic [[boost controller]]. The main function of a wastegate is to allow some of the exhaust to bypass the turbine when the set intake pressure is achieved.
 
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.<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}}{{dead link|date=February 2025|bot=medic}}{{cbignore|bot=medic}}</ref> 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 implementation of a turbocharger is to improve upon the size to output efficiency of an engine by solving for one of its cardinal limitations. A [[naturally aspirated]] 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 [[combustion chamber]]. This ability to fill the cylinder with air is its [[volumetric efficiency]]. 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. The intake pressure, in the absence of the turbocharger determined by the atmosphere, can be controllably increased with the turbocharger.
 
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.<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 [[Brown, Boveri & Cie]].<ref>Ernst Jenny: "Der BBC-Turbolader." Birkhäuser, Basel, 1993, ISBN 978-3-7643-2719-4. [https://zeitungsarchiv.nzz.ch/#read/11300/NZZ%20-%20Neue%20Z%C3%BCrcher%20Zeitung/1993-05-26/69 "Buchbesprechung."] [[Neue Zürcher Zeitung]], 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>
The application of a compressor to increase pressure at the point of cylinder air intake is often referred to as [[forced induction]]. [[Centrifugal supercharger]]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 heat energy from the exhaust gas that would otherwise be wasted, into useful work. Superchargers use output energy to achieve a net gain, which is at the expense of some of the engine's total output.
 
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 [[Chevrolet Corvair#First generation (1960–1964)|Chevrolet Corvair Monza]] and the [[Oldsmobile Jetfire]], 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=[[Autocar (magazine)|Autocar]] |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 |archive-date=14 April 2019 |archive-url=https://web.archive.org/web/20190414062841/http://www.turbos.bwauto.com/en/products/turbochargerHistory.aspx |url-status=dead }}</ref>
==Fuel efficiency==
 
The turbo succeeded in motorsport, but took its time. The [[1968 Indianapolis 500]] was the first to be won with a turbocharged engine; turbos have won on the fast oval track ever since. Porsche pioneered turbos in engines derived from the 1963 [[Porsche 911]], which had an air-cooled flat six engine just like the Chevrolet Corvair, but got turbocharged ten years later. [[Porsche 935]] and [[Porsche 936]] won both kinds of Sportcars World Championships in 1976, as well as the Le Mans 24h, proving that they could be reliable and fast. In Formula One, capacity was limited to only 1.5 litre, with the first race victories coming in the late 1970s, and the first F1 World Championship in 1983, with a [[BMW M10]]-based 4-cylinder engine that dates back to 1961.
Since a turbocharger increases the specific [[horsepower]] output of an engine, the engine will also produce increased amounts of [[waste heat]]. 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 lower [[compression ratio]] (more specifically, expansion ratio) of turbocharged engines contributes to slightly lower [[thermal efficiency]], which has a small but direct impact on overall [[fuel efficiency]].
 
Turbodiesel passenger cars appeared in the 1970s, with the Mercedes 300 D. Greater adoption of turbocharging in passenger cars began in the 1980s, as a way to increase the performance of smaller [[engine displacement|displacement]] engines.<ref name="Miller"/>
It is another form of cooling that has the largest impact on fuel efficiency: charge cooling. Even with the benefits of [[intercooled|intercooling]], the total compression in the [[combustion chamber]] is greater than that in a [[naturally-aspirated engine]]. To avoid [[Engine knock|knock]] 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, [[nitrogen]], it has a higher specific heat and more heat capacitance. It "holds" this heat until it is released in the [[exhaust gas|exhaust]] stream, preventing destructive [[Engine knock|knock]]. This thermodynamic property allows manufacturers to achieve good power output with common pump fuel at the expense of fuel economy and emissions. The optimum Air-to-Fuel ratio (A/F) for complete 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.
 
== Design ==
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 [[Variable geometry turbocharger]]). Currently, the [[Porsche 997#Turbo|Porsche 911 (997) Turbo]] 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 [[Twin-turbo|sequential turbocharging]], which uses a small turbocharger at low RPMs and a larger one at high RPMs.
 
[[File:Turbosuperchargers.png|thumb|Turbocharger components]]
The engine management systems of most modern vehicles can control [[boost (automotive engineering)|boost]] 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 [[Saab Automobile]] provides immediate feedback on the combustion while it is occurring using an electrical charge.
 
Like other forced induction devices, a [[centrifugal compressor|compressor]] in the turbocharger pressurises the intake air before it enters the [[inlet manifold]].<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 [[turbine]].<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>
The new 2.0L [[Gasoline direct injection|FSI]] turbo engine from [[Volkswagen]]/[[Audi]] 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.
 
The main components of the turbocharger are:
==Design details==
* Turbine – usually a [[radial turbine]] design
The [[ideal gas law]] 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.
* Compressor – usually a [[centrifugal compressor]]
* Center housing hub rotating assembly
 
===Turbine===
A turbo spins very fast; most peak between 80,000 and 200,000&nbsp;RPM (using low [[inertia]] 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 [[ball bearing]]s leading to failure so most turbo-chargers use [[fluid bearing]]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.
[[File:Turbo-turbine.jpg|thumb|upright=1.6|Turbine section of a [[Garrett_Motion|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 (mechanical engineering)|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.
Turbochargers with [[foil bearing]]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.
 
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.
To manage the ''upper-deck'' air pressure, the turbocharger's exhaust gas flow is regulated with a [[wastegate]] 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 [[solenoid]] to regulate the pressure fed to the wastegate membrane. This solenoid can be controlled by [[Automatic Performance Control]], the engine's [[electronic control unit]] 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.
 
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. [https://www.scribd.com/doc/17453088/How-Does-Variable-Turbine-Geometry-Work Variable Turbine Geometry].</ref> Various technologies, as described in the following sections, are often aimed at combining the benefits of both small turbines and large turbines.
Some turbochargers (normally called [[variable geometry turbocharger]]s) utilise 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 = [[12 December]] [[2006]]}}</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.
 
Large diesel engines often use a single-stage [[axial turbine|axial inflow turbine]] 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|url-access=subscription }}</ref>
The first production car to use these turbos was the limited-production [[1989]] [[Shelby CSX|Shelby CSX-VNT]], in essence a [[Dodge Shadow]] equipped with a 2.2L petrol engine. The Shelby CSX-VNT utilised a turbo from [[Garrett Systems|Garrett]], 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 [[Chrysler Corporation]] vehicles used this turbocharger in 1990, including the [[Dodge Daytona]] and [[Dodge Shadow]]. 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>[http://www.allpar.com/mopar/22t.html Allpar turbo engine history]</ref>
 
====Twin-scroll====
The 2006 [[Porsche 997|Porsche 911 Turbo]] has a twin turbocharged 3.6-litre flat six, and the turbos used are [[BorgWarner]]'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.
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 [[scavenging (engine)|scavenging]] 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 |archive-date=14 August 2012 |archive-url=https://web.archive.org/web/20120814060206/http://www.modified.com/tech/modp-0906-twin-scroll-turbo-system-design/ |url-status=dead }}</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>
==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 [[synthetic oil]]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 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 [[Coke (fuel)|coking]]<!-- 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 [[diesel engine]]s, due to the lower exhaust temperatures and generally slower engine speeds.
 
<gallery heights="150px" mode="packed">
A [[turbo timer]] 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 [[foil bearings]]. 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.
File:Mitsubishi twin-scroll turbo.JPG |Cutaway view showing the two scrolls of a [[Mitsubishi Motors|Mitsubishi]] twin-scroll (the larger scroll is illuminated in red)
File:Twin-scroll turbo T-GDI.jpg |Transparent exhaust manifold and turbo scrolls on a [[Hyundai Gamma engine]], showing the paired cylinders (1 & 4 and 2 & 3)
</gallery>
 
====Variable-geometry====
In custom applications utilising tubular headers rather than [[cast iron]] manifolds, the need for a cooldown period is reduced because the lighter headers store much less heat than heavy cast iron manifolds.
[[File:VariableGeometryTurbo 1.JPG|thumb|Cutaway view of a [[Porsche]] variable-geometry turbocharger]]{{Main|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 [[Actuator#Electric|electric actuator]] 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 [[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.<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.
==Lag==
A [[lag]] 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 [[rotational inertia]] and reach the speed necessary to supply boost pressure. The directly-driven compressor in a positive-displacement [[supercharger]] 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.
 
==== Electrically-assisted turbochargers ====
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 [[aspect ratio]] of the turbine by reducing the diameter and increasing the gas-flow path-length. Increasing the upper-deck air pressure and improving the [[wastegate]] response helps but there are cost increases and reliability disadvantages that car manufacturers are not happy about. Lag is also reduced by using a [[foil bearing]] 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.
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,{{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 [[electric supercharger]], which solely uses an electric motor to power the compressor.
 
=== Compressor ===
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 [[torque]], 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.
[[File:Turbo-compressor.jpg|thumb|upright=1.6|Compressor section of a [[Garrett_Motion|Garrett]] GT30 with the compressor housing removed]]
 
The [[centrifugal compressor|compressor]] draws in outside air through the engine's intake system, pressurises it, then feeds it into the [[combustion chamber]]s (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]].
Other setups, most notably in [[V engine|V-type engine]]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 [[Twin-turbo#Parallel Twin-Turbo|parallel twin-turbo]] system.
 
====Ported shroud====
Some car makers combat lag by using two small turbos (such as [[Kia]], [[Toyota]], [[Subaru]], [[Maserati]], [[Mazda]], and [[Audi]]). 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 [[Twin-turbo#Sequential Twin-turbo|sequential twin-turbo]]. 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 [[BMW E60]] [[BMW 5 Series|5-Series]] 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.
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===
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 turbo RPM at which the turbo is physically able to supply the requested boost level {{fact}}. 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''.
The center housing 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.
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>
 
== Supporting components ==
Race cars often utilise an [[Anti-Lag System]] to completely eliminate lag at the cost of reduced turbocharger life.
[[File:TurbochargedGasolineEngineFlowDiagram.png|thumb|upright=1.4|Schematic of a typical turbo petrol engine]]
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:
On modern [[diesel engine]]s, this problem is virtually eliminated by utilising a [[variable geometry turbocharger]].
* [[Intercooler]] - 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>
* [[Water injection (engine)|Water injection]] - 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>
* [[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 enter the turbine
* [[Blowoff valve]] - to prevent compressor stall when the throttle is closed
 
== Turbo lag and boost threshold {{anchor|Turbocharger lag|Lag}} ==
==Boost==
{{refimprove section|date=June 2022}}
[[Boost (automotive engineering)|Boost]] refers to the increase in [[Manifold absolute pressure|manifold pressure]] that is generated by the turbocharger in the [[intake]] path or specifically [[intake manifold]] that exceeds normal [[atmospheric pressure]]. This is also the level of boost as shown on a [[pressure gauge]], usually in [[bar (unit)|bar]], [[Pound-force per square inch|psi]] or possibly [[pascal (unit)|kPa]] This is representative of the extra air pressure that is achieved over what would be achieved without the [[forced induction]]. Manifold pressure should not be confused with the amount, or "weight" of air that a turbo can flow.
 
'''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 [[throttle response]], 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.
Boost pressure is limited to keep the entire engine system including the turbo inside its design operating range by controlling the [[wastegate]] which shunts the exhaust gases away from the exhaust side turbine. In some cars the maximum boost depends on the fuel's [[octane rating]] and is electronically regulated using a [[engine knocking|knock]] [[sensor]], see [[Automatic Performance Control]] (APC).
 
Methods to reduce turbo lag include:{{citation needed|date=June 2022}}
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.
* 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-geometry turbocharger|variable-nozzle]] or [[#Twin-scroll|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<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 |archive-date=21 November 2017 |archive-url=https://web.archive.org/web/20171121110212/http://www.acarplace.com/cars/turbochargers.html |url-status=dead }}</ref> and [[hybrid turbocharger]]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.
==Applications==
Turbocharging is very common on [[diesel engine]]s in conventional automobiles, in [[truck]]s, [[locomotives]], 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:
* [[Naturally-aspirated engine|Naturally-aspirated]] diesels have lower power-to-weight ratios compared to gasoline engines; turbocharging will improve this P:W ratio.
* Diesel engines require more robust construction because they already run at very high [[compression ratio]] 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.
 
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.
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. [[Saab Automobile|Saab]] is a leader in production car turbochargers, starting with the [[1978]] [[Saab 99]]; all current Saab models are turbocharged. The [[Porsche 944]] 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 [[Porsche 928]].
 
== Use of several turbochargers ==
[[Chrysler Corporation]] was an innovator of turbocharger use in the [[1980s]]. Many of their production vehicles, for example the [[Chrysler LeBaron]], [[Dodge Daytona]], [[Dodge Shadow]]/[[Plymouth Sundance]] twins, and the [[Dodge Spirit]]/[[Plymouth Acclaim]] 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 [[PT Cruiser]] Turbo, the [[Dodge SRT-4]] and the [[Dodge Caliber]] SRT-4.
{{main|Twin-turbo}}
 
Some engines use several 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.
Small car turbos are increasingly being used as the basis for small [[jet engine]]s used for flying [[model aircraft]]—though the conversion is a highly specialised job—one not without its dangers. Jet engine enthusiasts have constructed home-built jet engines from automotive turbochargers, often running on [[propane]] and using a home-built combustion canister plumbed in between the high pressure side of the turbo's compressor and the intake side of the turbine. An oil supply for the bearings is still needed, usually provided by an electric pump. Starting such home-built jets is usually achieved by blowing air through the unit with a [[compressor]] or a domestic leaf-blower. Making these engines is not an easy task- unless the combustion canister design is correct the engine will either fail to start, fail to stabilise once running or even over-rev and destroy itself.
 
==Turbocharging versus supercharging==
Most modern turbocharged aircraft use an adjustable wastegate. The wastegate is controlled manually, or by a pneumatic/hydraulic control system, or, as is becoming more and more common, by a flight computer. In the interests of engine longevity, the wastegate is usually kept open, or nearly so, at sea-level to keep from overboosting the engine. As the aircraft climbs, the wastegate is gradually closed, maintaining the manifold pressure at or above sea-level. In aftermarket applications, aircraft turbochargers sometimes do not overboost the engine, but rather compress ambient air to sea-level pressure. For this reason, such aircraft are sometimes referred to as being turbo-normalised. Most applications produced by the major manufacturers (Beech, Cessna, Piper and others) increase the maximum engine intake air pressure by as much as 35%. Special attention to engine cooling and component strength is required because of the increased combustion heat and power.
{{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 [[crankshaft]]) whereas a turbocharger is powered by the kinetic energy of the engine's [[exhaust gas]].<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 [[exhaust heat management|heat soak]] the intake air.
[http://www.barber-nichols.com/products/specialty_products/turbo_alternators/default.asp Turbo-Alternator] is a form of turbocharger that generates electricity instead of boosting engine's air flow. On [[September 21]] [[2005]], [http://www.foresightvehicle.org.uk/ Foresight Vehicle] announced the first known implementation of such unit for automobiles, under the name [http://www.greencarcongress.com/2005/09/tigers_exhaust_.html TIGERS] (Turbo-generator Integrated Gas Energy Recovery System).
 
=== Twincharging ===
==History==
{{main|Twincharger}}
The turbocharger was invented by [[Switzerland|Swiss]] engineer Alfred Buchi, who had been working on steam turbines. His patent for the internal combustion turbocharger was applied for in [[1905]]. [[Diesel]] ships and locomotives with turbochargers began appearing in the [[1920s]].
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 ==
One of the first applications of a turbocharger to a non-Diesel engine came when [[General Electric]] engineer, Sanford Moss attached a turbo to a [[V12 engine|V12]] ''[[Liberty engine|Liberty]]'' aircraft engine. The engine was tested at [[Pikes Peak]] in [[Colorado]] at 14,000 feet to demonstrate that it could eliminate the power losses usually experienced in internal combustion engines as a result of altitude.
[[File:Schiffsdiesel.jpg|thumb|A medium-sized six-cylinder marine diesel-engine, with turbocharger and exhaust in the foreground]]
Turbochargers have been used in the following applications:
* [[Turbocharged petrol engine|Petrol-powered car engines]]
* [[Turbo-diesel|Diesel-powered car and van engines]]
* [[Forced induction in motorcycles|Motorcycle engines]] (quite rarely)
* Diesel-powered [[Truck#Engines_and_motors|truck engines]], beginning with a [[Saurer]] 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 |archive-date=26 July 2010 |archive-url=https://web.archive.org/web/20100726074209/http://www.turbodriven.com/en/turbofacts/default.aspx |url-status=dead }}</ref>
* [[Bus]] and [[Coach (bus)|coach]] diesel engines
* [[Aircraft_engine#Reciprocating_(piston)_engines|Aircraft piston engines]]
* [[Marine engine]]s
* [[Prime mover (locomotive)|Locomotive]] and [[diesel multiple unit]] engines for trains
* [[Stationary engine|Stationary/industrial engines]]
 
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 |archive-url =https://web.archive.org/web/20120913220705/http://honeywellbooster.com/assets/interview-honeywell-david-paja-craig-balis.pdf |url-status =usurped |archive-date =13 September 2012 |access-date=11 November 2011 }}</ref> The companies which manufacture the most turbochargers in Europe and the U.S. are [[Garrett Motion]] (formerly Honeywell), [[BorgWarner]] and [[Mitsubishi Heavy Industries|Mitsubishi Turbocharger]].<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 |archive-date=28 April 2012 |archive-url=https://web.archive.org/web/20120428193025/http://www.just-auto.com/analysis/turbochargers-european-growth-driven-by-spread-to-small-cars_id86995.aspx |url-status=dead }}</ref>
Turbochargers were first used in production aircraft engines in the 1930s prior to [[World War II]]. The primary purpose behind most aircraft-based applications was to increase the altitude at which the airplane can fly, by compensating for the lower [[atmospheric pressure]] present at high altitude. Aircraft such as the [[Lockheed P-38 Lightning]], [[Boeing B-17 Flying Fortress]] and [[B-29 Superfortress]] all used exhaust driven "turbo-superchargers" to increase high altitude engine power. It is important to note that turbosupercharged aircraft engines actually utilized a gear-driven [[centrifugal type supercharger]] in series with a turbocharger.
 
==Safety==
Turbo-Diesel trucks were produced in Europe and America (notably by [[Cummins]]) after [[1949]]. The turbocharger hit the automobile world in [[1952]] when [[Fred Agabashian]] qualified for pole position at the [[Indianapolis 500]] and led for 100 miles before tire shards disabled the blower.
Turbocharger failures and resultant high exhaust temperatures are among the causes of car fires.<ref>{{cite web |url=http://www.artsa.com.au/assets/library/ARTSA_Truck_Fires_Nov06.pdf |title=Why trucks catch fire |first=Peter |last=Hart |publisher=ARTSA Institute |___location=Australia |date=November 2006 |access-date=2025-08-15 |archive-url=https://web.archive.org/web/20150228202806/http://www.artsa.com.au/assets/library/ARTSA_Truck_Fires_Nov06.pdf |archive-date=2015-02-28 |url-status=dead}}</ref>
[[Image:Corvair turbo engine.jpg|right|thumb|250px|The [[Chevrolet Corvair|Corvair]]'s innovative turbocharged [[flat-6]] [[Chevrolet Corvair engine|engine]]; 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 [[General Motors Corporation|General Motors]]. The [[GM A platform|A-body]] [[Oldsmobile Cutlass]] Jetfire and [[Chevrolet Corvair]] 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 ''[[Oldsmobile V8 engine#Turbo Jetfire|Turbo Jetfire]]'' was a 215&nbsp;in³ (3.5&nbsp;L) [[V8]], while the [[Chevrolet Corvair engine|Corvair engine]] was either a 145&nbsp;in³ (2.3&nbsp;L)(1962-63) or a 164&nbsp;in³ (2.7&nbsp;L) (1964-66) [[flat-6]]. Both of these engines were abandoned within a few years, and GM's next turbo engine came more than ten years later.
 
Failure of the seals will cause oil to leak into the exhaust system causing blue-gray smoke or a [[runaway diesel]].
[[Offenhauser]]'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 [[Porsche]] dominated the [[Can-Am]] series with a 1100&nbsp;hp [[Porsche 917|917/30]]. Turbocharged cars dominated the [[24 Hours of Le Mans|Le Mans]] between [[1976]] and [[1994]].
 
==See also==
[[BMW]] led the resurgence of the automobile turbo with the [[1973]] [[BMW 2002|2002 Turbo]], with Porsche following with the [[Porsche 911|911 Turbo]], introduced at the [[1974]] [[Paris Motor Show]]. Buick was the first GM division to bring back the turbo, in the [[1978]] [[Buick Regal]], followed by the [[Mercedes-Benz]] [[Mercedes-Benz 300D|300D]] and [[Saab 99]] in [[1978]]. The worlds first production turbodiesel automobile was also introduced in [[1978]] by [[Peugeot]] with the launch of the [[Peugeot 604]] turbodiesel. Today, nearly all automotive diesels are turbocharged.
{{Commons category|Turbochargers}}
 
* [[Boost gauge]]
[[Alfa Romeo]] introduced first Italian (mass produced) turbocharged car Alfetta GTV 2000 Turbodelta in 1979, [[Pontiac]] also introduced a turbo in [[1980]] and [[Volvo Cars]] followed in [[1981]]. [[Renault]] however gave another step and installed a turbocharger to the smallest and lightest car they had, the [[Renault R5|R5]], making it the first [[Supermini car|Supermini]] 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 incredibly fast [[Ferrari 308]].
* [[Engine downsizing]]
 
* [[Exhaust pulse pressure charging]]
In [[Formula One]], 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 F1|Renault]], [[Honda F1|Honda]], [[BMW]]). 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 [[Fédération Internationale de l'Automobile|FIA]] 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}}.
* [[Hot vee turbocharged engine]]
 
In [[Rallying]], turbocharged engines of up to 2000cc have long been the preferred motive power for the Group A/[[WRC|World Rally Car]] (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 [[FIA]], 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, [[four-wheel-drive]] vehicles in rally competition, beginning with the [[Audi Quattro]], has led to exceptional road cars in the modern era such as the [[Subaru Impreza WRX]] and [[Mitsubishi Lancer Evolution]].
 
Although late to use turbocharging, [[Chrysler|Chrysler Corporation]] 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 liter four-cylinder engines in minivans, sedans, and coupes. Their 2.2 liter 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 liter engines had about 150 horsepower and had no intercooler. Though the company stopped using turbocharges in 1993, they returned to turbocharged engines in 2002 with their 2.4 liter engines, boosting output by 70 horsepower. <ref>[http://www.allpar.com/mopar/22t.html Chrysler turbocharged engines (Allpar)]</ref>
 
==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=[[Automobile Magazine]]
| date=February 2006
}}
<references/>
 
== See also ==
*[[Boost gauge]]
*[[Boost controller]]
*[[Twin-turbo]]
*[[Intercooler]]
*[[Turbo timer]]
*[[Supercharger]]
*[[Blow off valve]]
*[[Forced Induction]]
 
== External links ==
*[http://auto.howstuffworks.com/turbo.htm How turbochargers work at HowStuffWorks.com]
*[http://mohawkinnovative.com Mohawk Innovative Technology Inc.]
 
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