Editing Napier Lion (section)

==Design and development==
{{More citations needed section|date=December 2013}}
Early in the First World War, Napier were contracted to build aero engines to designs from other companies, initially a [[Royal Aircraft Establishment|Royal Aircraft Factory]] model and then [[Sunbeam Motor Car Company#Sunbeam-Coatalen engines|Sunbeams]]. Both engines proved to be unreliable and in 1916 Napier decided to design an engine with high power, light weight and low frontal area. Napier's engineers laid out the engine with its 12 cylinders in what they called a [[Broad arrow#In characterisation of internal combustion engines|"broad arrow"]]—three banks of four cylinders sharing a common crankshaft. The configuration is also known as a [[W engine]].<ref name="Wiley1936">{{cite book |last1=Domonoske |first1=Arthur Boquer |last2=Finch |first2=Volney Cecil |year=1936 |title=Aircraft Engines: Theory, Analysis, Design and Operation |url=https://books.google.com/books?id=qrc7AAAAMAAJ|type=Engineering textbook |publisher= J. Wiley & Sons |page=7 |quote=The W, or broad arrow engine, has three rows of cylinders of which the central row is vertical with the other two rows forming equal angles with the vertical.}}</ref> The engine was also advanced in form, the heads using four valves per cylinder with twin overhead [[camshaft]]s on each bank of cylinders and a single block being milled from [[aluminium]] instead of the common separate-cylinder steel construction used on almost all other designs. In contrast to the long stroke small bore engine designs typical of the period, the Lion engine was also well ahead of its time in being [[oversquare]], the cylinder bore diameter being larger than the crankshaft stroke, this allowing higher engine speeds and greater efficiency. 

[[File:Napier Lion cambox.jpg|thumb|left|Cutaway view showing the [[Overhead camshaft|double overhead camshaft]] arrangement]]

Under [[Arthur Rowledge]], the design of the engine, renamed Lion, was completed in 1917; hand-built prototypes ran later that year. It was fitted to an [[Airco DH.9]] in early 1918, and many cooling problems were observed during testing. The milled block was difficult to build with the required accuracy and the design reverted to separate aluminium cylinders. Both problems were solved by the middle of the year and the engine entered production in June 1918. The first Lion I versions delivered {{convert|450|hp|kW}} from their 24 [[litre]]s. The power output made the Lion the most powerful Allied aircraft engine, which had previously been the [[Liberty L-12]], producing {{convert|400|hp|kW}}.

As the most powerful engine available (particularly after a [[turbocharger]] became an option in 1922), the Lion went on to commercial success. Through the years between the wars the Lion was ubiquitous and Napier manufactured little else. They stopped making cars in 1925 and little thought was given to replacing their world-famous product. Between the wars the Lion engine powered over 160 different aircraft types.

[[File:Napier-Railton Engine Bay.jpg|thumb|The Napier Lion installed in the [[Napier-Railton]] car]]
In [[engine tuning|highly tuned]] racing versions, the engine could reach {{convert|1300|hp|kW|abbr=on}} and it was used to break many world height, air speed and distance records in aircraft and boats, delivering {{convert|1375|hp|kW|abbr=on}} in a highly tuned Lion for a water speed record of {{convert|100|mph|abbr=on}} in 1933. In land speed records, Lion engines powered many of [[Sir Malcolm Campbell]]'s [[:Category:Bluebird record-breaking vehicles|record breakers]] including a record of over {{convert|250|mph|abbr=on}} in 1932 and [[John Cobb (motorist)|John Cobb]]'s {{convert|394|mph|abbr=on}} ''[[Railton Mobil Special]]'' in 1947—a record that came well after the Lion had passed its prime and stood until the 1960s. The record had been held by British drivers for 32 years. Lions powered successful entrants in the most prestigious event in air racing, the [[Schneider Trophy]], in 1922 and 1927 but were dropped by [[Supermarine]] in favour of a new engine, the [[Rolls-Royce R]], which had been designed for racing.

During the 1930s a new generation of much larger and more powerful engines appeared and the Lion became uncompetitive. By the time the [[Bristol Hercules]] and the [[Rolls-Royce Merlin]] arrived in the late 1930s, the Lion was obsolete. The Sea Lion, a marine version of the Lion, was used to power high speed [[RAF Rescue Launch]]es.  The Lion aero engine was also adapted to power propeller-driven motor sleighs, which were used for high-speed transport and SAR duties on sea ice by the [[Finnish Air Force]] and Navy.

Turning away from the broad arrow layout, Napier designed new engines using the more compact [[H engine]] layout. The 16-cylinder [[Napier Rapier]] produced {{convert|400|hp|kW|abbr=on}} and the 24-cylinder [[Napier Dagger]] delivered just under {{convert|1000|hp|kW|abbr=on}}. The engines were smaller than contemporary designs from other companies and Napier started afresh with a new [[sleeve valve]] design, which evolved into the [[Napier Sabre]].