Editing Variable valve timing (section)

===Automotive===
The desirability of being able to vary the valve opening duration to match an engine's [[rotational speed]] first became apparent in the 1920s when maximum allowable RPM limits were generally starting to rise. Until about this time an engine's idle RPM and its operating RPM were very similar, meaning that there was little need for variable valve duration. The first use of variable valve timing was on the 1903 [[Cadillac Runabout and Tonneau]] created by [[Alanson Partridge Brush]] Patent 767,794 “INLET VALVE GEAR FOR INTERNAL COMBUSTION ENGINES” filed August 3, 1903, and granted August 16, 1904.<ref>{{cite web |title=The Forgotten Story Of Cadillac's Brass Era VTEC |url=https://jalopnik.com/the-forgotten-story-of-cadillacs-brass-era-vtec-1844463416 |website=Jalopnik |publisher=G/O media |access-date=12 January 2021}}</ref> Some time prior to 1919 Lawrence Pomeroy, Vauxhall's Chief Designer, had designed a 4.4&nbsp;L engine for a proposed replacement for the existing 30-98 model to be called the H-Type.<ref name="coomberbook">{{cite book |last=Coomber |first=Ian |date=5 December 2017 |title=Vauxhall: Britain's Oldest Car Maker |publisher=Fonthill Media |page=46 |isbn=978-1781556405 }}</ref> In this engine the single overhead camshaft was to move longitudinally to allow different camshaft lobes to be engaged. It was in the 1920s that the first [[patent]]s for variable duration valve opening started appearing – for example United States patent {{US-patent|1527456}}.

In 1958 [[Porsche]] made application for a German Patent, also applied for and published as British Patent GB861369 in 1959. The Porsche patent used an oscillating cam to increase the valve lift and duration. The [[desmodromic]] cam driven via a push/pull rod from an eccentric shaft or [[swashplate]]. It is unknown if any working prototype was ever made.

[[Fiat]] was the first auto manufacturer to patent a functional automotive variable valve timing system which included variable lift. Developed by Giovanni Torazza in the late 1960s, the system used hydraulic pressure to vary the fulcrum of the cam followers (US Patent 3,641,988).<ref name="freepatentsonline.com">{{cite web|url=http://www.freepatentsonline.com/3641988.html|title=VALVE-ACTUATING MECHANISM FOR AN INTERNAL COMBUSTION ENGINE |access-date=2011-01-12|work=freepatentsonline.com}}</ref> The hydraulic pressure changed according to engine speed and intake pressure. The typical opening variation was 37%.

[[Alfa Romeo]] was the first manufacturer to use a variable valve timing system in production cars (US Patent 4,231,330).<ref>{{cite web|url=http://www.freepatentsonline.com/4231330.html|title=Timing variator for the timing system of a reciprocating internal combustion engine |access-date=2011-01-12| work=freepatentsonline.com}}</ref><ref>{{Cite book |url=https://onlinelibrary.wiley.com/doi/book/10.1002/9781118354179 |title=Encyclopedia of Automotive Engineering |date=2014-04-17 |publisher=Wiley |isbn=978-0-470-97402-5 |editor-last=Crolla |editor-first=David |edition=1 |language=en |chapter=Trends—Spark Ignition |doi=10.1002/9781118354179.auto143 |editor-last2=Foster |editor-first2=David E. |editor-last3=Kobayashi |editor-first3=Toshio |editor-last4=Vaughan |editor-first4=Nicholas}}</ref> The fuel injected models of the 1980 [[Alfa Romeo Spider]] 2000 had a mechanical VVT system. The system was engineered by Ing Giampaolo Garcea in the 1970s.<ref name="alfaspiderfaq.org">{{cite web|url=http://alfaspiderfaq.org/spdrfaq_v3.pdf|title=Alfa Romeo Spider FAQ| access-date=2008-11-29| work=alfaspiderfaq.org}}</ref> All Alfa Romeo Spider models from 1983 onward used electronic VVT.<ref>{{cite book |last=Rees |first=Chris |title=Original Alfa Romeo Spider |url=https://archive.org/details/originalalfaspid00chri/page/102 |publisher=MBI Publishing 2001 |page=[https://archive.org/details/originalalfaspid00chri/page/102 102] |isbn=0-7603-1162-5 |year=2001 |url-access=registration }}</ref>

In 1989, [[Honda]] released the [[VTEC]] system.<ref>[http://asia.vtec.net/spfeature/vtecimpl/vtec1.html asia.vtec.net]</ref> While the earlier [[Nissan]] [[N-VCT|NVCS]] alters the phasing of the camshaft, VTEC switches to a separate cam profile at high engine speeds to improve peak power. The first VTEC engine Honda produced was the [[Honda Engines (B-series)#B16A|B16A]] which was installed in the [[Honda Integra|Integra]], [[Honda CRX|CRX]], and [[Honda Civic|Civic]] hatchback available in Japan and Europe.{{citation needed|date=July 2014}}

In 1992, Porsche first introduced [[VarioCam]], which was the first system to provide continuous adjustment (all previous systems used discrete adjustment). The system was released in the [[Porsche 968]] and operated on the intake valves only.

====Motorcycles====
Variable valve timing has been applied to motorcycle engines but was considered a non-useful "technological showpiece" as late as 2004 due to the system's weight penalty.<ref>{{cite book|title=Motorcycle Fuel Injection Handbook
|first=Adam |last=Wade|publisher=MotorBooks International|isbn=1610590945|year=2004|pages=149–150|url=https://books.google.com/books?id=wC2dThrY2BMC&pg=PA149}}</ref> Since then, motorcycles including VVT have included the [[Kawasaki 1400GTR|Kawasaki 1400GTR/Concours 14]] (2007), the [[Ducati Multistrada 1200]] (2015), the [[BMW R1250GS]] (2019) and the [[Yamaha YZF-R15]] V3.0 (2017), the Suzuki GSX-R1000R 2017 L7, the Moto Guzzi V85TT, the Harley Davidson Milwaukee-Eight, the KTM 1390 Super Duke.