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<blockquote data-quote="snowflake" data-source="post: 213924" data-attributes="member: 152"><p>google says</p><p>The desirability of being able to vary the valve opening duration to match an engine’s <a href="https://en.wikipedia.org/wiki/Rotational_speed" target="_blank">rotational speed</a> 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. It was in the 1920s that the first <a href="https://en.wikipedia.org/wiki/Patent" target="_blank">patents</a> for variable duration valve opening started appearing – for example United States patent <a href="https://www.google.com/patents/US1527456" target="_blank">U.S. Patent 1,527,456</a>.</p><p></p><p>In 1958 <a href="https://en.wikipedia.org/wiki/Porsche" target="_blank">Porsche</a> 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 <a href="https://en.wikipedia.org/wiki/Desmodromic" target="_blank">desmodromic</a> cam driven via a push/pull rod from an eccentric shaft or <a href="https://en.wikipedia.org/wiki/Swashplate" target="_blank">swashplate</a>. It is unknown if any working prototype was ever made.</p><p></p><p><a href="https://en.wikipedia.org/wiki/Fiat" target="_blank">Fiat</a> 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).<a href="https://en.wikipedia.org/wiki/Variable_valve_timing#cite_note-freepatentsonline.com-5" target="_blank">[5]</a> The hydraulic pressure changed according to engine speed and intake pressure. The typical opening variation was 37%.</p><p></p><p><a href="https://en.wikipedia.org/wiki/Alfa_Romeo" target="_blank">Alfa Romeo</a> was the first manufacturer to use a variable valve timing system in production cars (US Patent 4,231,330).<a href="https://en.wikipedia.org/wiki/Variable_valve_timing#cite_note-6" target="_blank">[6]</a> The fuel injected models of the 1980 <a href="https://en.wikipedia.org/wiki/Alfa_Romeo_Spider" target="_blank">Alfa Romeo Spider</a> 2000 had a mechanical VVT system. The system was engineered by Ing Giampaolo Garcea in the 1970s.<a href="https://en.wikipedia.org/wiki/Variable_valve_timing#cite_note-alfaspiderfaq.org-7" target="_blank">[7]</a></p><p></p><p>In 1987 <a href="https://en.wikipedia.org/wiki/Nissan" target="_blank">Nissan</a> debuted their electronic variable valve timing technology called <a href="https://en.wikipedia.org/wiki/N-VCT" target="_blank">NVCS</a> in their DOHC <a href="https://en.wikipedia.org/wiki/Nissan_VG_engine#VG20DET" target="_blank">VG20DET</a> and <a href="https://en.wikipedia.org/wiki/Nissan_VG_engine#VG30DE" target="_blank">VG30DE</a> engines. In 1989, <a href="https://en.wikipedia.org/wiki/Honda" target="_blank">Honda</a> released the <a href="https://en.wikipedia.org/wiki/VTEC" target="_blank">VTEC</a> system.<a href="https://en.wikipedia.org/wiki/Variable_valve_timing#cite_note-8" target="_blank">[8]</a> While the earlier <a href="https://en.wikipedia.org/wiki/Nissan" target="_blank">Nissan</a> <a href="https://en.wikipedia.org/wiki/N-VCT" target="_blank">NVCS</a> 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 <a href="https://en.wikipedia.org/wiki/Honda_Engines_(B-series)#B16A" target="_blank">B16A</a> which was installed in the <a href="https://en.wikipedia.org/wiki/Honda_Integra" target="_blank">Integra</a>, <a href="https://en.wikipedia.org/wiki/Honda_CRX" target="_blank">CRX</a>, and <a href="https://en.wikipedia.org/wiki/Honda_Civic" target="_blank">Civic</a> hatchback available in Japan and Europe.[<em><a href="https://en.wikipedia.org/wiki/Wikipedia:Citation_needed" target="_blank">citation needed</a></em>]</p><p></p><p>In 1992, Porsche first introduced <a href="https://en.wikipedia.org/wiki/VarioCam" target="_blank">VarioCam</a>, which was the first system to provide continuous adjustment (all previous systems used discrete adjustment). The system was released in the <a href="https://en.wikipedia.org/wiki/Porsche_968" target="_blank">Porsche 968</a> and operated on the intake valves only.</p></blockquote><p></p>
[QUOTE="snowflake, post: 213924, member: 152"] google says The desirability of being able to vary the valve opening duration to match an engine’s [URL='https://en.wikipedia.org/wiki/Rotational_speed']rotational speed[/URL] 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. It was in the 1920s that the first [URL='https://en.wikipedia.org/wiki/Patent']patents[/URL] for variable duration valve opening started appearing – for example United States patent [URL='https://www.google.com/patents/US1527456']U.S. Patent 1,527,456[/URL]. In 1958 [URL='https://en.wikipedia.org/wiki/Porsche']Porsche[/URL] 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 [URL='https://en.wikipedia.org/wiki/Desmodromic']desmodromic[/URL] cam driven via a push/pull rod from an eccentric shaft or [URL='https://en.wikipedia.org/wiki/Swashplate']swashplate[/URL]. It is unknown if any working prototype was ever made. [URL='https://en.wikipedia.org/wiki/Fiat']Fiat[/URL] 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).[URL='https://en.wikipedia.org/wiki/Variable_valve_timing#cite_note-freepatentsonline.com-5'][5][/URL] The hydraulic pressure changed according to engine speed and intake pressure. The typical opening variation was 37%. [URL='https://en.wikipedia.org/wiki/Alfa_Romeo']Alfa Romeo[/URL] was the first manufacturer to use a variable valve timing system in production cars (US Patent 4,231,330).[URL='https://en.wikipedia.org/wiki/Variable_valve_timing#cite_note-6'][6][/URL] The fuel injected models of the 1980 [URL='https://en.wikipedia.org/wiki/Alfa_Romeo_Spider']Alfa Romeo Spider[/URL] 2000 had a mechanical VVT system. The system was engineered by Ing Giampaolo Garcea in the 1970s.[URL='https://en.wikipedia.org/wiki/Variable_valve_timing#cite_note-alfaspiderfaq.org-7'][7][/URL] In 1987 [URL='https://en.wikipedia.org/wiki/Nissan']Nissan[/URL] debuted their electronic variable valve timing technology called [URL='https://en.wikipedia.org/wiki/N-VCT']NVCS[/URL] in their DOHC [URL='https://en.wikipedia.org/wiki/Nissan_VG_engine#VG20DET']VG20DET[/URL] and [URL='https://en.wikipedia.org/wiki/Nissan_VG_engine#VG30DE']VG30DE[/URL] engines. In 1989, [URL='https://en.wikipedia.org/wiki/Honda']Honda[/URL] released the [URL='https://en.wikipedia.org/wiki/VTEC']VTEC[/URL] system.[URL='https://en.wikipedia.org/wiki/Variable_valve_timing#cite_note-8'][8][/URL] While the earlier [URL='https://en.wikipedia.org/wiki/Nissan']Nissan[/URL] [URL='https://en.wikipedia.org/wiki/N-VCT']NVCS[/URL] 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 [URL='https://en.wikipedia.org/wiki/Honda_Engines_(B-series)#B16A']B16A[/URL] which was installed in the [URL='https://en.wikipedia.org/wiki/Honda_Integra']Integra[/URL], [URL='https://en.wikipedia.org/wiki/Honda_CRX']CRX[/URL], and [URL='https://en.wikipedia.org/wiki/Honda_Civic']Civic[/URL] hatchback available in Japan and Europe.[[I][URL='https://en.wikipedia.org/wiki/Wikipedia:Citation_needed']citation needed[/URL][/I]] In 1992, Porsche first introduced [URL='https://en.wikipedia.org/wiki/VarioCam']VarioCam[/URL], which was the first system to provide continuous adjustment (all previous systems used discrete adjustment). The system was released in the [URL='https://en.wikipedia.org/wiki/Porsche_968']Porsche 968[/URL] and operated on the intake valves only. [/QUOTE]
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