View source for W12 engine

{{refimprove|date=December 2009}}
[[File:LionEngine.jpg|thumb|A [[Napier Lion]] at [[Brooklands]] Motor Museum]]
A '''W12 engine''' is a twelve [[cylinder (engine)|cylinder]] [[reciprocating engine|piston]] [[internal combustion engine]] in a [[W engine|W configuration]].  W12 engines have been manufactured in two distinct configurations.  The original W12 configuration used three banks of four cylinders coupled to a common crankshaft, with 60° angles between the banks.  These were used in some early aircraft engines, notably including the [[Napier Lion]]. The more recent configuration, used in the [[#Volkswagen Group W12|Volkswagen Group W12]], uses four rows of three cylinders merged into two '[[cylinder bank]]s' (two narrow-angle [[VR6 engine]] blocks), coupled to a common [[crankshaft]].<ref name=AutoZine>{{cite web|url=http://www.autozine.org/technical_school/engine/tech_engine_packaging.htm#W12|title=Volkswagen's VR6 and W-engines - W12|first=Mark|last=Wan|work=AutoZine.org|accessdate=31 December 2009}}</ref>

==Aircraft engines (three-bank)==
===Napier Lion===
{{main|Napier Lion}}
The [[Napier Lion]] was a broad arrow-style W12 engine produced by [[Napier & Son|Napier]] at Acton, West London, from 1917 to the late 1930s.  This mostly alloy engine had a capacity of {{convert|24|L|cuin|0}} and produced from {{convert|450|to|900|hp|kW PS|0|lk=in}}.  It was used in many racing cars by [[John Cobb]] and [[Malcolm Campbell]], racing aircraft such as the [[Supermarine S.5]] [[Schneider Cup]] winner, and speed boats such as [[Hubert Scott-Paine]]'s [[Miss Britain III]].

===Other aircraft engines===
[[Lorraine-Dietrich|Lorraine]] manufactured their [[Lorraine 12E Courlis|12E Courlis]] aircraft engine in the 1920s and 1930s.

[[Sunbeam (car company)|Sunbeam]] built a prototype W12 called the "Kaffir", based on their [[Sunbeam Arab|Arab]] [[V8 engine]].

==Motor racing engines (three-bank)==
In the late 1980s, two W12 engines were designed and built for use in [[Formula One]].

===MGN===
In [[France]], [[Guy Negre]] produced the MGN which had three banks of four cylinders offset so that each crankpin accommodated three connecting rods side-by-side.  The MGN also had a novel system of cylindrical rotary valves located at the top of the [[combustion chamber]]s, making the engine notably compact.  The engine was tested in an AGS [[Formula One]] car, and in a Norma sports car, but never raced.

===Life F35===
{{main|Life Racing Engines}}
[[File:W12 Engine .jpg|thumb|[[Life Racing Engines]] F35]]
The other W12 [[Formula One]] engine was the Life F35 built in [[Italy]] by [[Life Racing Engines]].  The chief engineer for this project was [[Franco Rocchi]], who had already designed and built an experimental {{convert|498|cc|1}} W3 engine when he was at Ferrari in 1967 as an investigation into the viability of a [[W18 engine|W18]] F1 engine.<ref name="Ludvigsen, Life" >{{Cite book
 |title=The V12 Engine
 |last=Ludvigsen |first=Karl
 |authorlink=Karl Ludvigsen
 |publisher=Haynes Publishing
 |location=Sparkford, Yeovil
 |year=2005
 |isbn=1-84425-004-0
 |ref={{harvid|Ludvigsen|V12 Engine}}
  |pages=356–358 
}}</ref>  Rocchi's W3 engine used a central master connecting rod, with a slave rod locating onto each side of the master rod, rather than directly onto the crank pin.  This meant that there was no offset between the cylinders, and the crankpin did not have to be unusually long. A similar arrangement was employed for the Life W12 engine.<ref name="Ludvigsen, Life" /> Life Racing Engines failed to attract the interest of an existing team, so they acquired an F1 chassis which had been built for another team and tried to enter F1 on their own account in 1990. The engine proved to be unreliable and lacking in power.<ref name="Ludvigsen, Life" /><ref name="F1FailuresLife">{{cite book |last= Teaters|first= Matthew|year= 2011|title= Formula One Famous Failures|url= {{Google books|CZI9lsySYBkC|Formula One Famous Failures|plainurl=yes}}|chapter= 1990 Life Racing Engines|chapterurl= {{Google books|CZI9lsySYBkC|Formula One Famous Failures|page=62|plainurl=yes}}|location= |publisher= Trafford Publishing|isbn= 978-1-4251-8528-2|accessdate= 2013-12-17|quote= Best Result: 32nd fastest in Pre-Qualifying (Giacomelli, Imola)}}</ref> The car never got out of prequalifying in 14 attempts.<ref name="F1FailuresLife" />

==Audi Avus show car (three-bank)==
{{main|Audi Avus quattro}}
The Audi Avus prototype was shown at the 1991 [[Tokyo Motor Show]].<ref>Patton, Phil. {{Google books|SP7Sx5ps2F0C|Bug: The Strange Mutations of the World's Most Famous Automobile|page=240}}</ref> The engine was described as a traditional W12 with three banks of four cylinders each set at 60° to each other. The [[Overhead camshaft#Double overhead camshaft|DOHC]] W12 engine was said to produce {{convert|509|hp|kW|abbr=on}} at 5800&nbsp;rpm.<ref>{{cite journal |date= February 1992|chapterurl= {{Google books|uQEAAAAAMBAJ|Popular Science February 1992|page=29|plainurl=yes}}|editor1-last= Fred|editor1-first= Abatemarco|editor2-last= McCosh|editor2-first= Dan|title= Audi's bombshell|url= http://books.google.com.jm/books?id=uQEAAAAAMBAJ&source=gbs_navlinks_s|deadurl= no|chapter= Automotive Newsfront|journal= Popular Science|type= Scientific interest magazine|edition= US|location= New York, NY USA|publisher= Times Mirror Magazines|volume= 240|issue= 2|page= 29|issn= 0161-7370|accessdate= 2013-12-17|quote= Three sets of four cylinders are arranged in 60° intervals; the 12 connecting rods share four crankshaft journals, creating an unusually short block.|ref= }}</ref>

==Volkswagen Group W12==
[[File:Volkswagen W12.jpg|thumb|[[Volkswagen Group]] W12 engine from the [[Volkswagen Phaeton|Volkswagen Phaeton W12]]]]
At the 2001 Tokyo Motor Show, [[Volkswagen Group]] showcased a prototype [[Volkswagen Nardo|Volkswagen Nardo W12 Coupé]], a [[mid-engined]], [[rear-wheel drive]] [[supercar]] powered by a 6.0&nbsp;litre W12 engine, producing {{convert|600|hp|kW PS|0|lk=in}}.  A week before, the W12 Coupe broke the 24&nbsp;hour world endurance record.  A total distance of {{convert|7085.7|km|1}} was covered at an average speed of {{convert|295.24|km/h|2}}, breaking the old record by {{convert|12|km/h|1}}.  Production of the W12 Coupé was considered, but was subsequently cancelled.

[[Volkswagen Group]] currently produces [[list of Volkswagen Group petrol engines#W12|W12 engines]]. It is constructed by mating two narrow-angle 15° [[VR6 engine]]s at an inclined angle of 72°.<ref name=AutoZine/>  The narrow angle of each set of cylinders allows just two [[overhead camshaft]]s to drive each pair of banks, so just four are needed in total.  Note that this design differs from the [[W18 engine]] that Volkswagen Group produced for its [[Bugatti]] concept cars of 1998 and 1999.  Due to this distinction, the Volkswagen Group's W12 engine is sometimes described as a "WR12".

The 2011 Audi A8 debuted a revised 6.3 litre version of the W12 (WR12) engine with 500 PS.

The advantage of the W12 engine is its compact packaging, allowing Audi to build a 12-cylinder sedan with all-wheel drive, whereas a conventional [[V12 engine]] could only have a rear-wheel drive configuration as it would have no space in the engine bay for a differential and other components required to power the front wheels. The 6.0L W12 in the Audi A8L W12 (only offered in the long-wheelbase models) appears slightly smaller overall than the 4.2L V8 that powers the Audi A8 4.2 variants. 
<ref>{{cite web|url=http://www.newcartestdrive.com/review-intro.cfm?Vehicle=2005_Audi_A8&ReviewID=2934 |title=2005 Audi A8 Review and Photos |publisher=New Car Test Drive |date= |accessdate=2011-12-06}}</ref> 

The Volkswagen Group W12 engine is used in some high-end luxury models:
*[[Audi Avus quattro]] (concept version only)
*[[Audi A8|Audi A8L W12]]<ref>{{cite web|title=Audi A8L details|url=http://www.worldcarfans.com/104011211032/3|date=2004-01-12|publisher=Audi of America|work=WorldCarFans.com|accessdate=2009-08-26}}</ref>
*[[Bentley Continental GT]]
*[[Bentley_Continental_Flying_Spur_(2005)|Bentley Continental Flying Spur]]<ref>{{cite web|title=Continental Flying Spur specification|url=http://www.bentleymotors.com/models/continental_series/continental_flying_spur/specification/default.aspx|publisher=[[Bentley|Bentley Motors Limited]]|work=BentleyMotors.com|accessdate=2 September 2009}}</ref><ref>{{cite web|title=Continental Flying Spur Speed specification|url=http://www.bentleymotors.com/models/continental_series/continental_flying_spur_speed/specifications/default.aspx|publisher=[[Bentley|Bentley Motors Limited]]|work=BentleyMotors.com|accessdate=2 September 2009}}</ref>
*[[Spyker C12 La Turbie]]
*[[Spyker C12 Zagato]]
*[[Spyker D12|Spyker D12 Peking-to-Paris]] (prototype version only)
*[[Volkswagen Phaeton|Volkswagen Phaeton W12]]<ref>{{cite web|title=Volkswagen Phaeton - in depth|url=http://www.worldcarfans.com/102030111810/3|date=2002-03-01|publisher=[[Volkswagen Group|Volkswagen AG]]|work=WorldCarFans.com|accessdate=2009-08-26}}</ref>
*[[Volkswagen Touareg|Volkswagen Touareg W12]]
*[[Volkswagen Golf Mk5#GTI W12-650|Volkswagen GTI W12-650]] (prototype only)
*[[Volkswagen W12]]

==Museums==
Examples of these engines can be seen in some museums featuring collections of automotive engines or Aircraft engines such as:-
* [[Brooklands Museum]]

==References==
{{commons category|W12 engines}}
{{reflist}}

{{Piston engine configurations}}

{{wikipedia|W12 engine}}

[[Category:Piston engine configurations]]
[[Category:Engines with 12 cylinders]]
[[Category:W engines]]