Variable valve lift

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Variable valve lift (VVL) is an automotive piston engine technology which varies the height a valve opens in order to improve performance, fuel economy or emissions. There are two main types of VVL: discrete, which employs fixed valve lift amounts, and continuous, which is able to vary the amount of lift. Continuous valve lift systems typically allow for the elimination of the throttle (which is otherwise normally a single valve constricting the entire engine’s intake airway).[ citation needed ]

Contents

When used in conjunction with variable valve timing (VVT), variable valve lift can potentially offer infinite control over the intake and exhaust valve timing.[ citation needed ]

History

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). [1] The hydraulic pressure changed according to engine speed and intake pressure. The typical opening variation was 37%.

In September 1975, General Motors (GM) patented a system intended to vary valve lift. 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. GM encountered problems running at very low lift, and abandoned the project.[ citation needed ]

Discrete

Honda

In 1989, Honda released their Variable Valve Timing and Lift Electronic Control (VTEC) system. Which switches to a separate cam profile at high engine speeds to improve peak power. Later versions added VVT as well as three stage valve lift.

Nissan

Nissan introduced its Nissan Ecology Oriented Variable Valve Lift and Timing on its Nissan VVL engine it featured two-stage valve lift.

Toyota

Toyota's first VVL system was VVTL-i, a two-stage valve lift system that also incorporates variable valve timing. Like VTEC it has a normal and "wild" profile on the same camshaft. This system was only used on the 2ZZ-GE engine.

General Motors

General Motors (GM) introduced Intake Valve Lift Control (IVLC) on the third generation Ecotec engine. The system provides two-stage variable valve lift in addition to continuous variable timing. Continuously commanded by engine control unit, the valve rocker arm switches between high-lift and low-lift profiles on the camshaft, actuated by an oil control valve through a two-feed stationary hydraulic lash adjuster, allowing for either 4.0 or 10.5 mm lift. [2]

Fiat Chrysler Automobiles

Fiat Chrysler Automobiles added two-stage valve lift (VVL) to the 2016 update of its Pentastar engine along with improvements to its variable valve timing (VVT) system. [3]

Porsche

Porsche introduced VarioCam Plus which added two-stage intake valve lift to its VarioCam system.

Subaru

Subaru introduced i-Active Valve Lift System (i-AVLS) on the second-generation EJ25 (EJ253) which features two-stage intake lift, however it is only used on one of the two intake valves. second-generation EZ30 uses two stage lift shims, bucket, on all intake valves. For the EZ36D, it was replaced by D-AVCS, dual VVT on the intake/exhaust cams.

Mitsubishi

Mitsubishi introduced its Mitsubishi Innovative Valve timing and lift Electronic Control (MIVEC) in 1992, it featured two-stage valve lift.

Continuous

BMW

In 2001, BMW introduced the Valvetronic system. The Valvetronic system can continuously and precisely vary intake valve lift, and in addition, the independent Double VANOS system can concurrently vary the 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 pumping loss. The latter alone can boost both power output and fuel economy 10-15%. [4] Furthermore, both systems can also be combined with BMW DIVA (Differentiated Variable Air Intake) system which is the world's first continuously variable length intake manifold. As of 2017 BMW is the only company which can implement all three Variable Valve Timing, Lift and Intake Manifold in continuous adjustment form on production car.

Honda

Honda's Advanced VTEC, which does not appear in any of its production vehicles as of 2018, allows for continuously VVL versus its previous VTEC systems which had discrete lift settings. Although it was speculated that it would first be used in 2008 Honda Accord, the vehicle instead utilizes the existing i-VTEC system.

Mitsubishi

In 2005, Mitsubishi introduced continuously variable valve lift under the existing MIVEC name. [5] The system uses an intermediate, oscillating cam to alter the rocker arm fulcrum. [6]

Nissan

Nissan introduced its Variable Valve Event and Lift (VVEL) in 2007 as the world's second CVVL system. The first application was on the VQ37VHR V6 engine of Skyline Coupe (Infiniti G37). Nissan's system is more compact than BMW’s, involving fewer parts and less energy loss, and is therefore more adaptable to high-performance engines. [7] The VVEL does not use a conventional intake camshaft. Each valve is actuated by a cam which is pivoted on - but not fixed to - the camshaft. While conventional camshafts feature fixed rotating lobes, the cam in VVEL swings up and down; this is why it does not need a symmetric profile. Its movement is driven by the camshaft via a series of components. VVEL varies valve lift by the eccentric control shaft inside the rocker arm. By rotating the eccentric control shaft, the position of rocker arm is shifted, changing the swing angle of cam. The swing angle of cam determines the degree of valve lift. [7]

Toyota

Toyota introduced its Valvematic technology in 2008. Valvematic employs an intermediate shaft to achieve continuous variable valve lift. The intermediate shaft has an actuating member for each cylinder. [8] Each actuating member is made of two finger followers on either side of a roller bearing member. The followers can rotate in relation to the roller member by means of internal gear threads and an electric motor attached to the end of the intermediate shaft. The gear threads of the roller member and finger followers are in opposing directions. This means when the shaft swivels, the roller member and finger followers will move in opposing directions, moving either apart or closer together. In this way, the axle angle between them can be varied infinitely by the electric motor. The intake valve is actuated by camshaft via the intermediate shaft. [8] Specifically, the camshaft acts on the roller member of intermediate shaft, transferring the movement to both finger followers, then towards the roller rocker arms and ultimately to the intake valves. When the angle of the finger followers is narrow with respect to the roller member, valve lift is low. As the angle increases, so does valve lift. In this way, Valvematic can vary valve lift by adjusting the angle of the finger followers in relation to the roller bearing member.

Fiat Chrysler Automobiles

Fiat's Multiair technology which allows not only variable valve timing (VVT) and variable valve lift (VVL) but also a variable cam profile.

See also

Related Research Articles

<span class="mw-page-title-main">Camshaft</span> Mechanical component that converts rotational motion to reciprocal motion

A camshaft is a shaft that contains a row of pointed cams in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines, mechanically controlled ignition systems and early electric motor speed controllers.

<span class="mw-page-title-main">VTEC</span> Automobile variable valve timing technology

VTEC is a system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine, resulting in higher performance at high RPM, and lower fuel consumption at low RPM. The VTEC system uses two camshaft profiles and hydraulically selects between profiles. It was invented by Honda engineer Ikuo Kajitani. It is distinctly different from standard VVT systems which change only the valve timings and do not change the camshaft profile or valve lift in any way.

<span class="mw-page-title-main">Variable valve timing</span> Process of altering the timing of a valve lift event

Variable valve timing (VVT) is the process of altering the timing of a valve lift event in an internal combustion engine, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with variable valve lift systems. There are many ways in which this can be achieved, ranging from mechanical devices to electro-hydraulic and camless systems. Increasingly strict emissions regulations are causing many automotive manufacturers to use VVT systems.

<span class="mw-page-title-main">VVT-i</span> Automobile variable valve timing technology

VVT-i, or Variable Valve Timing with intelligence, is an automobile variable valve timing petrol engine technology manufactured by Toyota Group and used by brands Groupe PSA, Toyota, Lexus, Scion, Daihatsu, Subaru, Aston Martin, Pontiac and Lotus Cars. It was introduced in 1995 with the 2JZ-GE engine found in the JZS155 Toyota Crown and Crown Majesta.

<span class="mw-page-title-main">VANOS</span> BMW variable valve timing system

VANOS is a variable valve timing system used by BMW on various automotive petrol engines since 1992. The name is an abbreviation of the German words for variable camshaft timing.

<span class="mw-page-title-main">Nissan VVL engine</span> Reciprocating internal combustion engine

Nissan Ecology Oriented Variable Valve Lift and Timing is an automobile variable valve timing technology developed by Nissan. VVL varies the duration, and lift of valves by using hydraulic pressure switch between two different sets of camshaft lobes. VVT varies the valve timing throughout the RPM range. Together they function similarly to Honda's VTEC system.

VarioCam is an automobile variable valve timing technology developed by Porsche. VarioCam varies the timing of the intake valves by adjusting the tension on the timing chain connecting the intake and exhaust camshafts. VarioCam was first used on the 1992 3.0 L engine in the Porsche 968.

<span class="mw-page-title-main">MIVEC</span> Automobile variable valve timing technology

MIVEC (Mitsubishi Innovative Valve timing Electronic Control system) is the brand name of a variable valve timing (VVT) engine technology developed by Mitsubishi Motors. MIVEC, as with other similar systems, varies the timing of the intake and exhaust camshafts which increases the power and torque output over a broad engine speed range while also being able to help spool a turbocharger more quickly and accurately.

<span class="mw-page-title-main">Overhead camshaft engine</span> Valvetrain configuration

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<span class="mw-page-title-main">BMW N62</span> Reciprocating internal combustion engine

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<span class="mw-page-title-main">Nissan VK engine</span> Reciprocating internal combustion engine

The VK engine is a V8 piston engine from Nissan. It is an aluminum DOHC 4-valve design.

<span class="mw-page-title-main">Valvetronic</span> Automotive engine technology

The Valvetronic system is a BMW variable valve lift system which, in combination with VANOS, allows infinite adjustment of the intake valve timing and lift. The system claims to improve fuel economy and emissions, and negates the need for a throttle body in regular use.

Nissan Variable Timing control or Nissan Valve Timing Control System is an automobile variable valve timing technology developed by Nissan. N-VTC was first introduced in 1987 on the VG30DE and VG20DET engine.

<span class="mw-page-title-main">BMW N73</span> Reciprocating internal combustion engine

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<span class="mw-page-title-main">Mitsubishi 4A9 engine</span> Reciprocating internal combustion engine

The Mitsubishi 4A9 engine is the newest family range of all-alloy inline four-cylinder engines from Mitsubishi Motors, introduced in the 2004 version of their Mitsubishi Colt supermini, and built by DaimlerChrysler-owned MDC Power in Germany.

<span class="mw-page-title-main">Mitsubishi 4B1 engine</span> Reciprocating internal combustion engine

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<span class="mw-page-title-main">Variable Valve Event and Lift</span> Automobile variable valve timing technology

Nissan Variable Valve Event and Lift is an automobile variable valve timing technology developed by Nissan.

A helical camshaft is a type of mechanical variable valve actuation (VVA) system. More specifically, it is a camshaft that allows the valve opening duration to be varied over a wide, continuous, step-less range, with all of the added duration being at full valve lift.

<span class="mw-page-title-main">MultiAir</span> Automobile variable valve timing technology

MultiAir or Multiair is a hydraulically-actuated variable valve timing (VVT) and variable valve lift (VVL) engine technology enabling "cylinder by cylinder, stroke by stroke" control of intake air directly via a gasoline engine's inlet valves. Developed by Fiat Powertrain Technologies, the technology addresses a primary engine inefficiency: pumping losses caused by restricting intake passage by the throttle plate that regulates air feeding the cylinders.

Variable valve timing (VVT) is a system for varying the valve opening of an internal combustion engine. This allows the engine to deliver high power, but also to work tractably and efficiently at low power. There are many systems for VVT, which involve changing either the relative timing, duration or opening of the engine's inlet and exhaust valves.

References

  1. ↑ "VALVE-ACTUATING MECHANISM FOR AN INTERNAL COMBUSTION ENGINE". freepatentsonline.com. Retrieved 2011-01-12.
  2. ↑ "2014 Impala Engine Gets a High-Tech Lift". 17 September 2012.
  3. ↑ Swan, Tony. "Chrysler Reveals Major Revisions to Pentastar V-6". blog.caranddriver.com. Retrieved 22 January 2016.
  4. ↑ Interone Worldwide GmbH (2008-06-17). "Valvetronic | BMW Canada". Bmw.ca. Retrieved 2011-06-30.
  5. ↑ "Mitsubishi Innovative Valve Timing Electronic Control System". 2018-03-10. Archived from the original on 2018-03-10. Retrieved 2021-08-19.
  6. ↑ Stewart, Taj (2019-12-01). "Mitsubishi MIVEC (How it Works)" . Retrieved 2021-07-22.
  7. 1 2 Kiga, S. (2007). Development of Innovative Variable Valve Event and Lift (VVEL) System. Society of Automotive Engineers, 400 Commonwealth Dr, Warrendale, PA, 15096, USA. SAE Technical Paper Series.
  8. 1 2 Moriya, Y. (1996). Newly developed intelligent variable valve timing system - continuously controlled cam phasing as applied to a new 3 liter inline 6 engine. SAE Special Publications, (1171)
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