Variable Valve Timing - Revision history

203.82.79.101: /* VVT Implementations */

2009-06-19T08:10:12Z

VVT Implementations

← Older revision		Revision as of 08:10, 19 June 2009
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	* [[Porsche]] [[VarioCam]] - Varies intake timing by adjusting tension of a cam chain.		* [[Porsche]] [[VarioCam]] - Varies intake timing by adjusting tension of a cam chain.
	* [[Porsche]] [[VarioCam Plus]] - Varies intake valve timing by rotating the cam in relation to the cam sprocket as well as duration, timing and lift of the intake and exhaust valves by switching between two different sets of cam lobes.		* [[Porsche]] [[VarioCam Plus]] - Varies intake valve timing by rotating the cam in relation to the cam sprocket as well as duration, timing and lift of the intake and exhaust valves by switching between two different sets of cam lobes.
	* [[Proton (company)\|Proton]] [[Campro engine#Campro CPS and VIM engine\|Campro CPS]] - said to be based on Lotus technology which developed Porsche's VarioCam. ~~Available since 2008~~. ~~Now fitted~~ in Proton Gen-2, Proton Waja and Proton Exora.		* [[Proton (company)\|Proton]] [[Campro engine#Campro CPS and VIM engine\|Campro CPS]] - said to be based on Lotus technology which developed Porsche's VarioCam. Varies intake valve timing and lift by switching between 2 sets of cam lobes without using rocker arms as in most variable valve timing systems. Debuted in the 2008 Proton Gen-2 CPS, 2008 Proton Waja CPS and 2009 Proton Exora.
	* [[PSA Peugeot Citroën]] CVVT - Continuous variable valve timing.		* [[PSA Peugeot Citroën]] CVVT - Continuous variable valve timing.
	* [[Renault Clio 182, Clio Cup and Clio V6 Mk2]] VVT - variable valve timing.		* [[Renault Clio 182, Clio Cup and Clio V6 Mk2]] VVT - variable valve timing.

203.82.79.101: /* VVT Implementations */

2009-06-19T08:04:26Z

VVT Implementations

← Older revision		Revision as of 08:04, 19 June 2009
Line 58:		Line 58:
	* [[Porsche]] [[VarioCam]] - Varies intake timing by adjusting tension of a cam chain.		* [[Porsche]] [[VarioCam]] - Varies intake timing by adjusting tension of a cam chain.
	* [[Porsche]] [[VarioCam Plus]] - Varies intake valve timing by rotating the cam in relation to the cam sprocket as well as duration, timing and lift of the intake and exhaust valves by switching between two different sets of cam lobes.		* [[Porsche]] [[VarioCam Plus]] - Varies intake valve timing by rotating the cam in relation to the cam sprocket as well as duration, timing and lift of the intake and exhaust valves by switching between two different sets of cam lobes.
	* [[Proton (company)\|Proton]] [[Campro engine#Campro CPS and VIM engine\|Campro CPS]] - ~~Still under development,~~ said to be based on Lotus technology which developed Porsche's VarioCam.		* [[Proton (company)\|Proton]] [[Campro engine#Campro CPS and VIM engine\|Campro CPS]] - said to be based on Lotus technology which developed Porsche's VarioCam. Available since 2008. Now fitted in Proton Gen-2, Proton Waja and Proton Exora.
	* [[PSA Peugeot Citroën]] CVVT - Continuous variable valve timing.		* [[PSA Peugeot Citroën]] CVVT - Continuous variable valve timing.
	* [[Renault Clio 182, Clio Cup and Clio V6 Mk2]] VVT - variable valve timing.		* [[Renault Clio 182, Clio Cup and Clio V6 Mk2]] VVT - variable valve timing.

Red marquis: /* External links */

2008-10-29T11:12:40Z

External links

← Older revision		Revision as of 11:12, 29 October 2008
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	[[Category:Engine technology]]		[[Category:Engine technology]]
	~~[[Category:Engines]]~~

Red marquis at 07:36, 11 August 2007

2007-08-11T07:36:22Z

← Older revision		Revision as of 07:36, 11 August 2007
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	[[Image:~~K20 head~~.jpg\|thumb\|right\|400px~~\| The [[i-VTEC]] system found in the [[Honda]] [[Honda K engine\|K20Z3]].~~]]		[[Image:Variable Valve engine.jpg\|thumb\|right\|400px]]
	'''Variable Valve Timing''', or '''VVT''', is a generic term for an [[automobile]] [[piston engine]] technology. VVT allows the ''lift'' or ''duration'' or ''timing'' (some or all) of the [[intake]] or [[exhaust]] [[Poppet valve\|valves]] (or both) to be changed while the engine is in operation. [[Two stroke cycle\|Two-stroke]] engines use a [[2-stroke power valve system\|Power valve system]] to get similar results to VVT.		'''Variable Valve Timing''', or '''VVT''', is a generic term for an [[automobile]] [[piston engine]] technology. VVT allows the ''lift'' or ''duration'' or ''timing'' (some or all) of the [[intake]] or [[exhaust]] [[Poppet valve\|valves]] (or both) to be changed while the engine is in operation. [[Two stroke cycle\|Two-stroke]] engines use a [[2-stroke power valve system\|Power valve system]] to get similar results to VVT.
	==Overview==		==Overview==

Red marquis: /* History */

2007-08-11T07:33:59Z

History

← Older revision		Revision as of 07:33, 11 August 2007
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	In 1986, [[Nissan]] developed their own form of VVT with the [[Nissan VG engine\|VG30DE(TT)]] engine for their Mid-4 Concept. [[Nissan]] chose to focus their [[N-VCT#N-VCT\|NVCS]] ([[Nissan]] Valve-Timing Control System) mainly at low and medium speed torque production because the vast majority of the time, engine RPMs will not be at extremely high speeds. The [[N-VCT#N-VCT\|NVCS]] system can produce both a smooth idle, and high amounts of low and medium speed torque. Although it can help a little at the top-end also, the main focus of the system is low and medium range torque production. The [[Nissan VG engine\|VG30DE]] engine was first used in the [[300ZX]] (Z31) 300ZR model in 1987, this was the first production car to use electronically controlled VVT technology.		In 1986, [[Nissan]] developed their own form of VVT with the [[Nissan VG engine\|VG30DE(TT)]] engine for their Mid-4 Concept. [[Nissan]] chose to focus their [[N-VCT#N-VCT\|NVCS]] ([[Nissan]] Valve-Timing Control System) mainly at low and medium speed torque production because the vast majority of the time, engine RPMs will not be at extremely high speeds. The [[N-VCT#N-VCT\|NVCS]] system can produce both a smooth idle, and high amounts of low and medium speed torque. Although it can help a little at the top-end also, the main focus of the system is low and medium range torque production. The [[Nissan VG engine\|VG30DE]] engine was first used in the [[300ZX]] (Z31) 300ZR model in 1987, this was the first production car to use electronically controlled VVT technology.

	Honda's VTEC motorcycle engine employed on the Japanese market-only Honda CBR400F in 1983 provided as a technology basis for VTEC. The next step was taken in 1989 by [[Honda]] with the [[VTEC]] system. [[Honda]] had started production of a system that gives an engine the ability to operate on two completely different cam profiles, eliminating a major compromise in engine design. One profile designed to operate the valves at low engine speeds provides good road manners, low fuel consumption and low emissions output. The second is a high lift, long duration profile and comes into operation at high engine speeds to provide an increase in power output. The [[VTEC]] system was also further developed to provide other functions in engines designed primarily for low fuel consumption. 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. In 1991 the [[Acura]]/[[Honda]] [[Honda NSX\|NSX]] powered by the [[Honda_C_engine#C30A\|C30A]] became the first [[VTEC]] equipped vehicle available in the ~~[[United_States\|~~US]]. [[VTEC]] can be considered the first "cam switching" system and is also one of only a few currently in production.		Honda's VTEC motorcycle engine employed on the Japanese market-only Honda CBR400F in 1983 provided as a technology basis for VTEC. The next step was taken in 1989 by [[Honda]] with the [[VTEC]] system. [[Honda]] had started production of a system that gives an engine the ability to operate on two completely different cam profiles, eliminating a major compromise in engine design. One profile designed to operate the valves at low engine speeds provides good road manners, low fuel consumption and low emissions output. The second is a high lift, long duration profile and comes into operation at high engine speeds to provide an increase in power output. The [[VTEC]] system was also further developed to provide other functions in engines designed primarily for low fuel consumption. 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. In 1991 the [[Acura]]/[[Honda]] [[Honda NSX\|NSX]] powered by the [[Honda_C_engine#C30A\|C30A]] became the first [[VTEC]] equipped vehicle available in the US. [[VTEC]] can be considered the first "cam switching" system and is also one of only a few currently in production.

	In 1991, Clemson University researchers patented the Clemson Camshaft which was designed to provide continuously variable valve timing independently for both the intake and exhaust valves on a single camshaft assembly. This ability makes it suitable for both [[pushrod]] and [[overhead cam]] engine applications.<ref>American Society of Mechanical Engineers (1991-12-01), Clemson Camshaft improves auto economy, Mechanical Engineering-CIME </ref>		In 1991, Clemson University researchers patented the Clemson Camshaft which was designed to provide continuously variable valve timing independently for both the intake and exhaust valves on a single camshaft assembly. This ability makes it suitable for both [[pushrod]] and [[overhead cam]] engine applications.<ref>American Society of Mechanical Engineers (1991-12-01), Clemson Camshaft improves auto economy, Mechanical Engineering-CIME </ref>

Red marquis: /* History */

2007-08-11T07:33:40Z

History

← Older revision		Revision as of 07:33, 11 August 2007
Line 14:		Line 14:

	==History==		==History==
	[[Fiat]] was the first auto manufacturer to patent a functional 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). The hydraulic pressure changed according to engine speed and intake pressure. The typical opening variation was 37%.		[[Fiat]] was the first auto manufacturer to patent a functional 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). The hydraulic pressure changed according to engine speed and intake pressure. The typical opening variation was 37%.

	In September [[1975]], [[General_Motors\|General Motors]] patented a system intended to vary valve lift. [[General_Motors\|GM]] was interested in throttling the intake valves in order to reduce emissions. This was done by minimizing the amount of lift at low load to keep the intake velocity higher, thereby atomizing the intake charge. [[General_Motors\|GM]] encountered problems running at very low lift, and abandoned the project.		In September 1975, [[General_Motors\|General Motors]] patented a system intended to vary valve lift. [[General_Motors\|GM]] was interested in throttling the intake valves in order to reduce emissions. This was done by minimizing the amount of lift at low load to keep the intake velocity higher, thereby atomizing the intake charge. [[General_Motors\|GM]] encountered problems running at very low lift, and abandoned the project.

	[[Alfa Romeo]] was the first manufacturer to use a variable valve timing system in production cars (US Patent 4,231,330). The [[1980]] [[Alfa Romeo Spider]] 2.0 L had a mechanical VVT system in Spica fuel injected cars sold in the [[USA]]. Later this was also used in the [[1983]] [[Alfa Romeo Alfetta\|Alfetta]] 2.0 Quadrifoglio Oro models as well as other cars.		[[Alfa Romeo]] was the first manufacturer to use a variable valve timing system in production cars (US Patent 4,231,330). The 1980 [[Alfa Romeo Spider]] 2.0 L had a mechanical VVT system in Spica fuel injected cars sold in the USA. Later this was also used in the 1983 [[Alfa Romeo Alfetta\|Alfetta]] 2.0 Quadrifoglio Oro models as well as other cars.

	In [[1986]], [[Nissan]] developed their own form of VVT with the [[Nissan VG engine\|VG30DE(TT)]] engine for their Mid-4 Concept. [[Nissan]] chose to focus their [[N-VCT#N-VCT\|NVCS]] ([[Nissan]] Valve-Timing Control System) mainly at low and medium speed torque production because the vast majority of the time, engine RPMs will not be at extremely high speeds. The [[N-VCT#N-VCT\|NVCS]] system can produce both a smooth idle, and high amounts of low and medium speed torque. Although it can help a little at the top-end also, the main focus of the system is low and medium range torque production. The [[Nissan VG engine\|VG30DE]] engine was first used in the [[300ZX]] (Z31) 300ZR model in [[1987]], this was the first production car to use electronically controlled VVT technology.		In 1986, [[Nissan]] developed their own form of VVT with the [[Nissan VG engine\|VG30DE(TT)]] engine for their Mid-4 Concept. [[Nissan]] chose to focus their [[N-VCT#N-VCT\|NVCS]] ([[Nissan]] Valve-Timing Control System) mainly at low and medium speed torque production because the vast majority of the time, engine RPMs will not be at extremely high speeds. The [[N-VCT#N-VCT\|NVCS]] system can produce both a smooth idle, and high amounts of low and medium speed torque. Although it can help a little at the top-end also, the main focus of the system is low and medium range torque production. The [[Nissan VG engine\|VG30DE]] engine was first used in the [[300ZX]] (Z31) 300ZR model in 1987, this was the first production car to use electronically controlled VVT technology.

	Honda's ~~[[VTEC#VTEC_in_motorcycles\|~~ VTEC motorcycle engine]] employed on the Japanese market-only Honda CBR400F in [[1983]] provided as a technology basis for VTEC. The next step was taken in [[1989]] by [[Honda]] with the [[VTEC]] system. [[Honda]] had started production of a system that gives an engine the ability to operate on two completely different cam profiles, eliminating a major compromise in engine design. One profile designed to operate the valves at low engine speeds provides good road manners, low fuel consumption and low emissions output. The second is a high lift, long duration profile and comes into operation at high engine speeds to provide an increase in power output. The [[VTEC]] system was also further developed to provide other functions in engines designed primarily for low fuel consumption. 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. In [[1991]] the [[Acura]]/[[Honda]] [[Honda NSX\|NSX]] powered by the [[Honda_C_engine#C30A\|C30A]] became the first [[VTEC]] equipped vehicle available in the [[United_States\|US]]. [[VTEC]] can be considered the first "cam switching" system and is also one of only a few currently in production.		Honda's VTEC motorcycle engine employed on the Japanese market-only Honda CBR400F in 1983 provided as a technology basis for VTEC. The next step was taken in 1989 by [[Honda]] with the [[VTEC]] system. [[Honda]] had started production of a system that gives an engine the ability to operate on two completely different cam profiles, eliminating a major compromise in engine design. One profile designed to operate the valves at low engine speeds provides good road manners, low fuel consumption and low emissions output. The second is a high lift, long duration profile and comes into operation at high engine speeds to provide an increase in power output. The [[VTEC]] system was also further developed to provide other functions in engines designed primarily for low fuel consumption. 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. In 1991 the [[Acura]]/[[Honda]] [[Honda NSX\|NSX]] powered by the [[Honda_C_engine#C30A\|C30A]] became the first [[VTEC]] equipped vehicle available in the [[United_States\|US]]. [[VTEC]] can be considered the first "cam switching" system and is also one of only a few currently in production.

	In [[1991]], [[Clemson University]] researchers patented the Clemson Camshaft which was designed to provide continuously variable valve timing independently for both the intake and exhaust valves on a single camshaft assembly. This ability makes it suitable for both [[pushrod]] and [[overhead cam]] engine applications.<ref>American Society of Mechanical Engineers (1991-12-01), Clemson Camshaft improves auto economy, Mechanical Engineering-CIME </ref>		In 1991, Clemson University researchers patented the Clemson Camshaft which was designed to provide continuously variable valve timing independently for both the intake and exhaust valves on a single camshaft assembly. This ability makes it suitable for both [[pushrod]] and [[overhead cam]] engine applications.<ref>American Society of Mechanical Engineers (1991-12-01), Clemson Camshaft improves auto economy, Mechanical Engineering-CIME </ref>

	In [[1992]] [[BMW]] introduced the [[VANOS]] system. Like the [[Nissan]] [[N-VCT#N-VCT\|NVCS]] system it could provide timing variation for the intake cam in steps (or phases), the [[VANOS]] system differed in that it could provide one additional step for a total of three. Then in [[1998]] the [[VANOS#Double_VANOS\|Double Vanos]] system was introduced which significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy. [[VANOS#Double_VANOS\|Double Vanos]] was the first system which could provide electronically controlled, continuous timing variation for both the intake and exhaust valves. In [[2001]] [[BMW]] introduced the [[Valvetronic]] system. The [[Valvetronic]] system is unique in that it can continuously vary intake valve lift, in addition to timing for both the intake and exhaust valves. The precise control the system has over the intake valves allows for the intake charge to be controlled entirely by the intake valves, eliminating the need for a [[throttle]] valve and greatly reducing [[Parasitic loss\|pumping loss]]. The reduction of [[Parasitic loss\|pumping loss]] accounts for more than a 10% increase in power output and fuel economy.		In 1992 [[BMW]] introduced the [[VANOS]] system. Like the [[Nissan]] [[N-VCT#N-VCT\|NVCS]] system it could provide timing variation for the intake cam in steps (or phases), the [[VANOS]] system differed in that it could provide one additional step for a total of three. Then in 1998 the [[VANOS#Double_VANOS\|Double Vanos]] system was introduced which significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy. [[VANOS#Double_VANOS\|Double Vanos]] was the first system which could provide electronically controlled, continuous timing variation for both the intake and exhaust valves. In 2001 [[BMW]] introduced the [[Valvetronic]] system. The [[Valvetronic]] system is unique in that it can continuously vary intake valve lift, in addition to timing for both the intake and exhaust valves. The precise control the system has over the intake valves allows for the intake charge to be controlled entirely by the intake valves, eliminating the need for a [[throttle]] valve and greatly reducing [[Parasitic loss\|pumping loss]]. The reduction of [[Parasitic loss\|pumping loss]] accounts for more than a 10% increase in power output and fuel economy.

	Ford became the first manufacturer to use variable valve timing in a pickup-truck, with the top-selling [[Ford F-series]] in the [[2004]] model year. The engine used was the [[Ford_Triton#3-valve\|5.4L 3-valve Triton]].		Ford became the first manufacturer to use variable valve timing in a pickup-truck, with the top-selling [[Ford F-series]] in the 2004 model year. The engine used was the [[Ford_Triton#3-valve\|5.4L 3-valve Triton]].

	In [[2005]] [[General Motors Corporation\|General Motors]] offered the first Variable Valve timing system for [[pushrod engine\|I-head]] V6 engines, [[GM High Value engine #3.5\|''LZE'' and ''LZ4'']].		In 2005 [[General Motors Corporation\|General Motors]] offered the first Variable Valve timing system for [[pushrod engine\|I-head]] V6 engines, [[GM High Value engine #3.5\|''LZE'' and ''LZ4'']].

	In [[2007]] [[DaimlerChrysler]] became the first manufacturer to produce a cam-in-block engine with independent control of exhaust cam timing relative to the intake. The 2008 [[Dodge Viper]] uses Mechadyne's concentric camshaft assembly to help boost power output to 600 Bhp.		In 2007 [[DaimlerChrysler]] became the first manufacturer to produce a cam-in-block engine with independent control of exhaust cam timing relative to the intake. The 2008 [[Dodge Viper]] uses Mechadyne's concentric camshaft assembly to help boost power output to 600 Bhp.

	==VVT Implementations==		==VVT Implementations==

Red marquis at 07:31, 11 August 2007

2007-08-11T07:31:24Z

New page

[[Image:K20 head.jpg|thumb|right|400px| The [[i-VTEC]] system found in the [[Honda]] [[Honda K engine|K20Z3]].]]
'''Variable Valve Timing''', or '''VVT''', is a generic term for an [[automobile]] [[piston engine]] technology. VVT allows the ''lift'' or ''duration'' or ''timing'' (some or all) of the [[intake]] or [[exhaust]] [[Poppet valve|valves]] (or both) to be changed while the engine is in operation. [[Two stroke cycle|Two-stroke]] engines use a [[2-stroke power valve system|Power valve system]] to get similar results to VVT.
==Overview==

[[Piston engine]]s normally use [[Poppet valve#Internal combustion engine|poppet valve]]s for intake and exhaust. These are driven (directly or indirectly) by [[cam]]s on a [[camshaft]]. The cams open the valves (''lift'') for a certain amount of time (''duration'') during each intake and exhaust cycle. The ''timing'' of the valve opening and closing is also important. The camshaft is driven by the crankshaft through [[timing belt]]s, [[gear]]s or [[Roller chain|chain]]s.

The profile, or position and shape of the cam lobes on the shaft, is optimized for a certain engine [[rpm]], and this tradeoff normally limits low-end [[torque]] or high-end [[Horsepower|power]]. VVT allows the cam profile to change, which results in greater efficiency and power.

At high engine speeds, an engine requires large amounts of air. However, the intake valves may close before all the air has been given a chance to flow in, reducing performance.

On the other hand, if the cam keeps the valves open for longer periods of time, as with a racing cam, problems start to occur at the lower engine speeds. This will cause unburnt fuel to exit the engine since the valves are still open. This leads to lower engine performance and increased emissions.

Pressure to meet environmental goals and fuel efficiency standards is forcing car manufacturers to turn to VVT as a solution. Most simple VVT systems (like [[Mazda]]'s [[S-VT]]) advance or retard the timing of the intake or exhaust valves. Others (like [[Honda]]'s [[VTEC]]) switch between two sets of cam lobes at a certain engine RPM. Still others (like [[BMW]]'s [[Valvetronic]]) can alter timing and lift continuously, which is called [[Continuous variable valve timing]] or CVVT.

==History==
[[Fiat]] was the first auto manufacturer to patent a functional 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). The hydraulic pressure changed according to engine speed and intake pressure. The typical opening variation was 37%.

In September [[1975]], [[General_Motors|General Motors]] patented a system intended to vary valve lift. [[General_Motors|GM]] was interested in throttling the intake valves in order to reduce emissions. This was done by minimizing the amount of lift at low load to keep the intake velocity higher, thereby atomizing the intake charge. [[General_Motors|GM]] encountered problems running at very low lift, and abandoned the project.

[[Alfa Romeo]] was the first manufacturer to use a variable valve timing system in production cars (US Patent 4,231,330). The [[1980]] [[Alfa Romeo Spider]] 2.0 L had a mechanical VVT system in Spica fuel injected cars sold in the [[USA]]. Later this was also used in the [[1983]] [[Alfa Romeo Alfetta|Alfetta]] 2.0 Quadrifoglio Oro models as well as other cars.

In [[1986]], [[Nissan]] developed their own form of VVT with the [[Nissan VG engine|VG30DE(TT)]] engine for their Mid-4 Concept. [[Nissan]] chose to focus their [[N-VCT#N-VCT|NVCS]] ([[Nissan]] Valve-Timing Control System) mainly at low and medium speed torque production because the vast majority of the time, engine RPMs will not be at extremely high speeds. The [[N-VCT#N-VCT|NVCS]] system can produce both a smooth idle, and high amounts of low and medium speed torque. Although it can help a little at the top-end also, the main focus of the system is low and medium range torque production. The [[Nissan VG engine|VG30DE]] engine was first used in the [[300ZX]] (Z31) 300ZR model in [[1987]], this was the first production car to use electronically controlled VVT technology.

Honda's [[VTEC#VTEC_in_motorcycles| VTEC motorcycle engine]] employed on the Japanese market-only Honda CBR400F in [[1983]] provided as a technology basis for VTEC. The next step was taken in [[1989]] by [[Honda]] with the [[VTEC]] system. [[Honda]] had started production of a system that gives an engine the ability to operate on two completely different cam profiles, eliminating a major compromise in engine design. One profile designed to operate the valves at low engine speeds provides good road manners, low fuel consumption and low emissions output. The second is a high lift, long duration profile and comes into operation at high engine speeds to provide an increase in power output. The [[VTEC]] system was also further developed to provide other functions in engines designed primarily for low fuel consumption. 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. In [[1991]] the [[Acura]]/[[Honda]] [[Honda NSX|NSX]] powered by the [[Honda_C_engine#C30A|C30A]] became the first [[VTEC]] equipped vehicle available in the [[United_States|US]]. [[VTEC]] can be considered the first "cam switching" system and is also one of only a few currently in production.

In [[1991]], [[Clemson University]] researchers patented the Clemson Camshaft which was designed to provide continuously variable valve timing independently for both the intake and exhaust valves on a single camshaft assembly. This ability makes it suitable for both [[pushrod]] and [[overhead cam]] engine applications.<ref>American Society of Mechanical Engineers (1991-12-01), Clemson Camshaft improves auto economy, Mechanical Engineering-CIME </ref>

In [[1992]] [[BMW]] introduced the [[VANOS]] system. Like the [[Nissan]] [[N-VCT#N-VCT|NVCS]] system it could provide timing variation for the intake cam in steps (or phases), the [[VANOS]] system differed in that it could provide one additional step for a total of three. Then in [[1998]] the [[VANOS#Double_VANOS|Double Vanos]] system was introduced which significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy. [[VANOS#Double_VANOS|Double Vanos]] was the first system which could provide electronically controlled, continuous timing variation for both the intake and exhaust valves. In [[2001]] [[BMW]] introduced the [[Valvetronic]] system. The [[Valvetronic]] system is unique in that it can continuously vary intake valve lift, in addition to timing for both the intake and exhaust valves. The precise control the system has over the intake valves allows for the intake charge to be controlled entirely by the intake valves, eliminating the need for a [[throttle]] valve and greatly reducing [[Parasitic loss|pumping loss]]. The reduction of [[Parasitic loss|pumping loss]] accounts for more than a 10% increase in power output and fuel economy.

Ford became the first manufacturer to use variable valve timing in a pickup-truck, with the top-selling [[Ford F-series]] in the [[2004]] model year. The engine used was the [[Ford_Triton#3-valve|5.4L 3-valve Triton]].

In [[2005]] [[General Motors Corporation|General Motors]] offered the first Variable Valve timing system for [[pushrod engine|I-head]] V6 engines, [[GM High Value engine #3.5|''LZE'' and ''LZ4'']].

In [[2007]] [[DaimlerChrysler]] became the first manufacturer to produce a cam-in-block engine with independent control of exhaust cam timing relative to the intake. The 2008 [[Dodge Viper]] uses Mechadyne's concentric camshaft assembly to help boost power output to 600 Bhp.

==VVT Implementations==
* Aftermarket Modifications - Conventional hydraulic tappet can be engineered to rapidly bleed-down for variable reduction of valve opening and duration.
* [[Alfa Romeo]] [[Alfa Romeo Twin Spark engine|Twin Spark]] - TS stands for "Twinspark" engine, it is equipped with Variable Valve Timing technology.
* [[BMW]] [[Valvetronic]] - Provides continuously variable lift for the intake valves; used in conjunction with Double VANOS.
* [[BMW]] [[VANOS]] - Varies intake timing by rotating the [[camshaft]] in relation to the gear.
* [[BMW]] [[VANOS#Double_VANOS|Double VANOS]] - Continuously varies the timing of the intake and exhaust valves.
* [[Ford Motor Company|Ford]] [[Variable Cam Timing (Ford)|Variable Cam Timing]] - Varies valve timing by rotating the camshaft.
* [[DaimlerChrysler]] - Varies valve timing thought the use of concentric camshafts developed by Mechadyne enabling dual-independent inlet/exhaust valve adjustment on the 2008 [[Dodge Viper]].
* [[General Motors Corporation|GM]] VVT - Varies valve timing continuously throughout the RPM range for both intake and exhaust for improved performance in both [[pushrod|overhead valve]] and [[overhead cam]] engine applications.(See also [[Northstar System]]).
* [[General Motors Corporation|GM]] [[GM Family 1 engine#DCVCP|DCVCP]] (Double Continuous Variable Cam Phasing) - Varies timing with [[hydraulic]] vane type phaser (see also [[GM Family II engine#LE5|Ecotec LE5]]).
* [[Holden]] [[Alloytec]] - Continuously variable camshaft phasing for inlet cams. Continuously variable camshaft phasing for inlet cams and exhaust cams (High Output Alloytec).
* [[Honda]] [[VTEC]] - Varies duration, timing and lift by switching between two different sets of cam [[lobe]]s.
* [[Honda]] [[VTEC#i-VTEC|i-VTEC]] - In high-output [[Overhead_cam#Double_overhead_camshafts|DOHC]] [[Straight-4|4 cylinder]] engines the [[VTEC#i-VTEC|i-VTEC]] system adds continuous intake cam phasing (timing) to traditional [[VTEC]]. In economy oriented [[Overhead_cam#Single_overhead_camshaft|SOHC]] and [[Overhead_cam#Double_overhead_camshafts|DOHC]] [[Straight-4|4 cylinder]] engines the [[VTEC#i-VTEC|i-VTEC]] system increases engine efficiency by delaying the closure of the intake valves under certain conditions and by using an electronically controlled throttle valve to reduce [[Parasitic loss|pumping loss]]. In [[Overhead_cam#Single_overhead_camshaft|SOHC]] [[V6]] engines the [[VTEC#i-VTEC|i-VTEC]] system is used to provide [[Variable Cylinder Management]] which deactivates one bank of 3 cylinders during low demand operation.
* [[Honda]] [[VTEC#SOHC_VTEC-E|VTEC-E]] - Unlike most [[VTEC]] systems [[VTEC#SOHC_VTEC-E|VTEC-E]] is not a cam switching system, instead it uses the [[VTEC]] mechanism to allow for a lean intake charge to be used by closing one intake valve under certain conditions.
* [[Hyundai Motor Group|Hyundai]] MPI CVVT - Varies power, torque, exhaust system, and engine response.
* [[Kawasaki]] - Varies position of cam by changing oil pressure thereby advancing and retarding the valve timing, [[Kawasaki_ZG-1000_Concours#2008_Concours14|2008 Concours 14]].
* [[Lexus]] [[VVT-iE]] - Continuously varies the intake camshaft timing using an electric actuator.
* [[Mazda]] [[S-VT]] - Varies timing by rotating the [[camshaft]].
* [[Mitsubishi Motors|Mitsubishi]] [[MIVEC]] - Continuously varies valve timing, duration and lift by switching between two different sets of cam lobes. The [[Mitsubishi 4B1 engine|4B1]] engine series uses a different variant of MIVEC which varies timing (phase) of both intake and exhaust camshafts continuously.
* [[Nissan]] [[N-VCT]] - Varies the rotation of the cam(s) only, does not alter lift or duration of the valves.
* [[Nissan]] [[VVL]] - Varies timing, duration, and lift of the intake and exhaust valves by using two different sets of cam [[lobe]]s.
* [[Nissan]] [[VVT]] introduced with the HR15DE HR16DE [[MR18DE MR20DE]] new engines in September 2004 on the [[Nissan Tiida]] and north american version named [[Nissan Versa]] (in 2007); and finally the [[Nissan Sentra]] (in 2007).
* [[Porsche]] [[VarioCam]] - Varies intake timing by adjusting tension of a cam chain.
* [[Porsche]] [[VarioCam Plus]] - Varies intake valve timing by rotating the cam in relation to the cam sprocket as well as duration, timing and lift of the intake and exhaust valves by switching between two different sets of cam lobes.
* [[Proton (company)|Proton]] [[Campro engine#Campro CPS and VIM engine|Campro CPS]] - Still under development, said to be based on Lotus technology which developed Porsche's VarioCam.
* [[PSA Peugeot Citroën]] CVVT - Continuous variable valve timing.
* [[Renault Clio 182, Clio Cup and Clio V6 Mk2]] VVT - variable valve timing.
* [[MG Rover Group|Rover]] [[VVC]] - Varies timing with an eccentric disc.
* [[Suzuki]] - VVT - [[Suzuki M engine]]
* [[Subaru]] [[AVCS]] - Varies timing (phase) with [[hydraulic]] pressure, used on turbocharged and six-cylinder Subaru engines.
* [[Subaru]] [[AVLS]] - Varies duration, timing and lift by switching between two different sets of cam lobes (similar to Honda VTEC). Used by non-turbocharged Subaru engines.
* [[Toyota]] [[VVT]] - Toyota [[Toyota A engine#20_Valve_4A-GE|4A-GE 20-Valve engine]] introduced VVT in the 1992 Corolla GT-versions.
* [[Toyota]] [[VVT-i]] - Continuously varies the timing of the intake camshaft, or both the intake and exhaust camshafts (depending on application).
* [[Toyota]] [[VVTL-i]] - Continuously varies the timing of the intake valves. Varies duration, timing and lift of the intake and exhaust valves by switching between two different sets of cam lobes.
* [[Volkswagen]] - VVT introduced with the 1.8T engine. The intake timing intentionally runs advanced and a retard point is calculated by the ECU. A hydraulic tensioner retards the intake timing.
* [[Volvo]] - VVT
* [[Yamaha]] - VCT (Variable Cam Timing) Varies position of cam thereby advancing and retarding the valve timing.

==See also ==
*[[Camless|Camless engine technology]]
*[[Variable Length Intake Manifold]]
*[[Continuous variable valve timing]]

==References==
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<references />
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==External links==
*[http://powrehaus.com/2007/01/26/powre-valvz/ Powre Haus Powre Valvz retrofit almost any engine]
*[http://www.mechadyne-int.com/vva-home/dodge-viper Mechadyne International's information on the Dodge Viper VVT system]
*[http://world.honda.com/automobile-technology/VTEC/ Honda Technology Picture Book, VTEC]
*[http://delphi.com/manufacturers/auto/powertrain/gas/valvetrain/vcp/ Delphi Variable Cam Phasers (VCP)]

[[Category:Engine technology]]
[[Category:Engines]]