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57-584: MIVEC was first introduced in 1992 in their 4G92 powerplant, a 1,597 cc naturally aspirated DOHC 16 valve straight-4 . At the time, the first generation of the system was named Mitsubishi Innovative Valve timing and lift Electronic Control . The first cars to use this were the Mitsubishi Mirage hatchback and the Mitsubishi Lancer sedan . While the conventional 4G92 engine provided 145 PS (107 kW; 143 hp) at 7000  rpm ,

114-709: A gasoline direct injection (GDI) version of the 4G93. This GDI model saw a production of over a million units though it was a heavy polluter therefore only sold in the Japanese market. A partially cleaned up version (with less power) was later sold in Europe, and was among the first of the modern GDI engines. It brought good fuel economy and, if well serviced, long engine life. 4G93 SOHC 16 Valve MPI 4G93 SOHC 16 Valve Carburetor 4G93 DOHC 16 Valve MPI 4G93T DOHC 16 Valve Turbo 4G93 DOHC 16 Valve GDI 4G93 DOHC 16 Valve GDI Turbo Applications The 4G94

171-480: A power valve system to get similar results to VVT. The valves within an internal combustion engine are used to control the flow of the intake and exhaust gases into and out of the combustion chamber . The timing, duration and lift of these valve events has a significant impact on engine performance. Without variable valve timing or variable valve lift , the valve timing is the same for all engine speeds and conditions, therefore compromises are necessary to achieve

228-474: A 4.4 L engine for a proposed replacement for the existing 30-98 model to be called the H-Type. 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 patents for variable duration valve opening started appearing – for example United States patent U.S. patent 1,527,456 . In 1958 Porsche made application for

285-478: 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

342-415: A VVT system requires a complex system, such as multiple cam profiles or oscillating cams. Late intake valve closing (LIVC) The first variation of continuous variable valve timing involves holding the intake valve open slightly longer than a traditional engine. This results in the piston actually pushing air out of the cylinder and back into the intake manifold during the compression stroke. The air which

399-480: A bore and stroke of 78.4 mm × 77.5 mm (3.09 in × 3.05 in) for a total displacement of 1.5 L (1,496 cc). With a 9.5:1 compression ratio and DOHC, four-valve-per-cylinder head and multi-point EFI , this engine produces 115 PS (85 kW; 113 hp) at 6,000  rpm and 135 N⋅m (100 lb⋅ft) at 5,000 rpm. The 4G91 was a short-lived model, mainly built between 1991 and 1995 and rarely seen in export markets. There

456-467: A brief period, boosting torque. From the 4B1 engine family onward, MIVEC has evolved into a continuous variable valve timing (CVVT) system (dual VVT on intake and exhaust valves). Many older implementations only vary the valve timing (the amount of time per engine revolution that the intake port is open) and not the lift. Timing is continuously independently controlled to provide four optimized engine-operating modes: Mitsubishi's 4N1 engine family

513-533: A cam phaser, controlled by the ECM, which continuously varies advancement or retardation of the camshaft timing. In 2007, Caterpillar developed the C13 and C15 Acert engines which used VVT technology to reduce NOx emissions, to avoid the use of EGR after 2002 EPA requirements. In 2010, Mitsubishi developed and started mass production of its 4N13 1.8 L DOHC I4, the world's first passenger car diesel engine that features

570-420: A centrally located high-lift cam. Each of the intake valves is operated by a low-lift cam and rocker arm, while placing a T-lever between them allows the valves to follow the action of the high-lift cam. At low speeds, The T-lever's wing section floats freely, enabling the low-lift cams to operate the valves. The intake rocker arms contain internal pistons, which are retained by springs in a lowered position while

627-540: A claimed 10–20 percent improvement in fuel economy. Modulated Displacement was dropped around 1996. Mitsubishi 4G9 engine The Mitsubishi 4G9 engine is a series of straight-4 automobile engines produced by Mitsubishi Motors . All are 16-valve, and use both single- and double- overhead camshaft heads. Some feature MIVEC variable valve timing , and it was the first modern gasoline direct injection engine upon its introduction in August 1996. The 4G91 uses

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684-521: A conventional cam lobe, while others use an eccentric cam lobe and a connecting rod. The principle is similar to steam engines, where the amount of steam entering the cylinder was regulated by the steam "cut-off" point. The advantage of this design is that adjustment of lift and duration is continuous. However, in these systems, lift is proportional to duration, so lift and duration cannot be separately adjusted. The BMW ( valvetronic ), Nissan ( VVEL ), and Toyota ( valvematic ) oscillating cam systems act on

741-447: A mechanical VVT system. The system was engineered by Ing Giampaolo Garcea in the 1970s. All Alfa Romeo Spider models from 1983 onward used electronic VVT. In 1989, Honda released the VTEC system. While the earlier Nissan 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

798-400: A passenger car diesel engine . Variable valve control systems optimize more power and torque by varying valve opening times and/or duration. Some of these valve control systems optimize performance at low and mid-range engine speeds, while others focus on enhancing only high-rpm power. The MIVEC system provides both of these benefits by controlling valve timing and lift. The basic operation of

855-403: A variable valve timing system. Manufacturers use many different names to describe their implementation of the various types of variable valve timing systems. These names include: This method uses two cam profiles, with an actuator to swap between the profiles (usually at a specific engine speed). Cam switching can also provide variable valve lift and variable duration, however the adjustment

912-673: Is a 2.0 L (1,999 cc) version built in Japan , used in the Mitsubishi Lancer . It has a cast iron engine block with Multi-point fuel injection and an aluminum SOHC cylinder head with forged steel connecting rods and four valves per cylinder. The 4G94 Also comes in the GDI DOHC variant which can be found in the Mitsubishi Galant. 4G94 SOHC 16 Valve MPI 4G94 DOHC 16 Valve GDI Applications Applications Continuous variable valve timing Variable valve timing ( VVT )

969-471: Is acted on by two lobes simultaneously. Each camshaft has a phasing mechanism which allows its angular position relative to the engine's crankshaft to be adjusted. One lobe controls the opening of a valve and the other controls the closing of the same valve, therefore variable duration is achieved through the spacing of these two events. The drawbacks to this design include: This system is not known to be used in any production engines. The operating principle

1026-419: Is discrete rather than continuous. The first production use of this system was Honda's VTEC system. VTEC changes hydraulic pressure to actuate a pin that locks the high lift, high duration rocker arm to an adjacent low lift, low duration rocker arm(s). Many production VVT systems are the cam phasing type, using a device known as a variator which changes the phase (Phase refers to the relative timing between

1083-429: Is driven by the crankshaft through timing belts , gears or chains . An engine requires large amounts of air when operating at high speeds. However, the intake valves may close before enough air has entered each combustion chamber, reducing performance. On the other hand, if the camshaft keeps the valves open for longer periods of time, as with a racing cam, problems start to occur at the lower engine speeds. Opening

1140-449: Is expelled fills the manifold with higher pressure, and on subsequent intake strokes the air which is taken in is at a higher pressure. Late intake valve closing has been shown to reduce pumping losses by 40% during partial load conditions, and to decrease nitric oxide ( NOx ) emissions by 24%. Peak engine torque showed only a 1% decline, and hydrocarbon emissions were unchanged. Early intake valve closing (EIVC) Another way to decrease

1197-413: Is freed from this constraint, allowing performance to be improved over the engine operating range. Piston engines normally use valves which are driven by camshafts . The cams open ( lift ) the valves kind for a certain amount of time ( duration ) during each intake and exhaust cycle. The timing of the valve opening and closing, relative to the position of the crankshaft, is important. The camshaft

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1254-446: Is of this type. Also known as "combined two shaft coaxial combined profile with helical movement", this system is not known to be used in any production engines. It has a similar principle to the previous type, and can use the same base duration lobe profile. However instead of rotation in a single plane, the adjustment is both axial and rotational giving a helical or three-dimensional aspect to its movement. This movement overcomes

1311-405: Is that it significantly lowers the temperature of the combustion chamber, which can increase hydrocarbon emissions. Early intake valve opening Early intake valve opening is another variation that has significant potential to reduce emissions. In a traditional engine, a process called valve overlap is used to aid in controlling the cylinder temperature. By opening the intake valve early, some of

1368-435: Is that the cam and follower profiles must be carefully designed to minimise contact stress (due to the varying profile). Ferrari is commonly associated with this system, however it is unknown whether any production models to date have used this system. This system is not known to be used in any production engines. It consists of two (closely spaced) parallel camshafts, with a pivoting follower that spans both camshafts and

1425-408: Is that the one follower spans the pair of closely spaced lobes. Up to the angular limit of the nose radius the follower 'sees' the combined surface of the two lobes as a continuous, smooth surface. When the lobes are exactly aligned the duration is at a minimum (and equal to that of each lobe alone) and when at the extreme extent of their misalignment the duration is at a maximum. The basic limitation of

1482-506: 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. Two-stroke engines use

1539-418: Is the world's first to feature a variable valve timing system applied to passenger car diesel engines . In the early years of developing its MIVEC technology, Mitsubishi also introduced a variant dubbed MIVEC-MD (Modulated Displacement), a form of variable displacement . Under a light throttle load, the intake and exhaust valves in two of the cylinders would remain closed, and the reduced pumping losses gave

1596-414: Is two eccentric drives and controllers are needed for each cylinder (one for the intake valves and one for the exhaust valves), which increases complexity and cost. MG Rover is the only manufacturer that has released engines using this system. This system consists of a cam lobe that varies along its length (similar to a cone shape). One end of the cam lobe has a short duration/reduced lift profile, and

1653-610: The B16A which was installed in the Integra , CRX , and Civic hatchback available in Japan and Europe. 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. Variable valve timing has been applied to motorcycle engines but

1710-417: The camshaft 25 times per second, so the valve timing events have to occur at precise times to offer performance benefits. Electromagnetic and pneumatic camless valve actuators offer the greatest control of precise valve timing, but, in 2016, are not cost-effective for production vehicles. The history of the search for a method of variable valve opening duration goes back to the age of steam engines when

1767-421: The "cam swap" occurs automatically at a fixed engine speed . The Cam Switch operation is transparent to the driver, who is simply rewarded with a smooth flow of power. Two distinct cam profiles are used to provide two engine modes: a low-speed mode, consisting of low-lift cam profiles; and a high-speed mode. The low-lift cams and rocker arms - which drive separate intake valves - are positioned on either side of

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1824-548: 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. Some time prior to 1919 Lawrence Pomeroy, Vauxhall's Chief Designer, had designed

1881-495: The MIVEC system is altering the cam profiles and thus tailoring engine performance in response to driver input. In essence, MIVEC serves the same function as "swapping cams", something that car racers might do when modifying older-design engines to produce more power. However, such swaps come with a compromise - generally yielding either greater low-end torque or more high-end horsepower, but not both. MIVEC achieves both goals. With MIVEC,

1938-607: The MIVEC-equipped engine could achieve 175 PS (129 kW; 173 hp) at 7500 rpm. Similar improvements were seen when the technology was applied to the 1994 Mitsubishi FTO , whose top-spec GPX variant had a 6A12 1997 cc DOHC 24 valve V6 with peak power of 200 PS (147 kW; 197 hp) at 7500 rpm. The GR model, whose otherwise identical powerplant was not MIVEC-equipped, produced 170 PS (125 kW; 168 hp) at 7000 rpm by comparison. Although initially designed to enhance performance,

1995-493: The camshaft by the governor. The Serpollet steamcars produced very hot high pressure steam, requiring poppet valves, and these used a patented sliding camshaft mechanism, which not only varied the inlet valve cut-off but allowed the engine to be reversed. An early experimental 200 hp Clerget V-8 from the 1910s used a sliding camshaft to change the valve timing . Some versions of the Bristol Jupiter radial engine of

2052-430: The desired result in intake and exhaust efficiency . This has been described in simulations. Practical results will vary based on available ambient combustion cycle gases in a naturally aspirated system, or forced air geometry as well as fuel pulse width timing and other factors which may or may not be available on vehicles equipped with variable valve timing. An engine equipped with a variable valve timing actuation system

2109-479: The development of the Corliss valve . These were widely used in constant speed variable load stationary engines, with admission cutoff, and therefore torque, mechanically controlled by a centrifugal governor and trip valves . As poppet valves came into use, a simplified valve gear using a camshaft came into use. With such engines, variable cutoff could be achieved with variable profile cams that were shifted along

2166-470: The early 1920s incorporated variable valve timing gear, mainly to vary the inlet valve timing in connection with higher compression ratios. The Lycoming R-7755 engine had a Variable Valve Timing system consisting of two cams that can be selected by the pilot. One for take off, pursuit and escape, the other for economical cruising. The desirability of being able to vary the valve opening duration to match an engine's rotational speed first became apparent in

2223-564: The engine speed is below the MIVEC switchover point, to avoid contacting the high-lift T-shaped levers. At high speeds, hydraulic pressure elevates the hydraulic pistons, causing the T-lever to push against the rocker arm, which in turn makes the high-lift cam operate the valves. MIVEC switches to the higher cam profile as engine speed increases, and drops back to the lower cam profile as engine speed decreases. The reduced valve overlap in low-speed mode provides stable idling, while accelerated timing of

2280-421: The exhaust valve opens, and exhaust gas is pushed out of the cylinder and into the exhaust manifold by the piston as it travels upward. By manipulating the timing of the exhaust valve, engineers can control how much exhaust gas is left in the cylinder. By holding the exhaust valve open slightly longer, the cylinder is emptied more and ready to be filled with a bigger air/fuel charge on the intake stroke. By closing

2337-550: The inert/combusted exhaust gas will back flow out of the cylinder via the intake valve, where it cools momentarily in the intake manifold. This inert gas then fills the cylinder in the subsequent intake stroke, which aids in controlling the temperature of the cylinder and nitric oxide emissions. It also improves volumetric efficiency, because there is less exhaust gas to be expelled on the exhaust stroke. Early/late exhaust valve closing Early and late exhaust valve closing timing can be manipulated to reduce emissions. Traditionally,

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2394-437: The inlet and exhaust camshafts, expressed as an angular measure.) of the camshaft and valves. This allows continuous adjustment of the cam timing (although many early systems only used discrete adjustment), however the duration and lift cannot be adjusted. These designs use an oscillating or rocking motion in a part cam lobe, which acts on a follower. This follower then opens and closes the valve. Some oscillating cam systems use

2451-687: The intake valve while the exhaust valve is still open may cause unburnt fuel to exit the engine, leading to lower engine performance and increased emissions. According to engineer David Vizard's book "Building Horsepower", when both intake & exhaust are open simultaneously, the much-higher-pressure exhaust pushes the intake-charge back, out from the cylinder, polluting the intake-manifold with exhaust, in worst cases. Early variable valve timing systems used discrete (stepped) adjustment. For example, one timing would be used below 3500 rpm and another used above 3500 rpm. More advanced "continuous variable valve timing" systems offer continuous (infinite) adjustment of

2508-446: The intake valve's closing reduces backflow to improve volumetric efficiency, which helps increase engine output as well as reduce lift friction. High-speed mode takes advantage of the pulsating intake effect created by the mode's high lift and retarded timing of intake valve closure. The resulting reduced pumping loss of the larger valve overlap yields higher power output and a reduction in friction. The low- and high-speed modes overlap for

2565-412: The intake valves only. Eccentric cam drive systems operates through an eccentric disc mechanism which slows and speeds up the angular speed of the cam lobe during its rotation. Arranging the lobe to slow during its open period is equivalent to lengthening its duration. The advantage of this system is that duration can be varied independent of lift (however this system does not vary lift). The drawback

2622-421: 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%. Alfa Romeo was the first manufacturer to use a variable valve timing system in production cars (US Patent 4,231,330). The fuel injected models of the 1980 Alfa Romeo Spider 2000 had

2679-493: The most powerful 1.6-litre naturally aspirated engines . A modular displacement (MD) version of the 4G92 MIVEC was also produced – MD is Mitsubishi's cylinder deactivation system which helps improve fuel consumption. 4G92P SOHC 16 Valve 4G92 DOHC 16 Valve 4G92-MIVEC DOHC 16 Valve Applications The 4G93 is a 1.8 L (1,834 cc) engine available in both SOHC and DOHC versions. Turbocharged variants are also produced. In mid 1996 Mitsubishi released

2736-475: The original DOHC 16V form it produces 120 PS (88 kW; 118 hp). Later, a fuel-efficient SOHC version was added, but the 4G92 is best known in its high-performance MIVEC equipped DOHC version, which fully replaced "ordinary" DOHC in 1993. Power output was raised as high as 170 PS (125 kW; 168 hp), as found in the JDM Mirage Cyborg-ZR and 1992 Lancer MR, making it one of

2793-483: The other end has a longer duration/greater lift profile. In between, the lobe provides a smooth transition between these two profiles. By shifting area of the cam lobe which is in contact with the follower, the lift and duration can be continuously altered. This is achieved by moving the camshaft axially (sliding it across the engine) so a stationary follower is exposed to a varying lobe profile to produce different amounts of lift and duration. The downside to this arrangement

2850-616: The pumping losses associated with low engine speed, high vacuum conditions is by closing the intake valve earlier than normal. This involves closing the intake valve midway through the intake stroke. Air/fuel demands are so low at low-load conditions and the work required to fill the cylinder is relatively high, so Early intake valve closing greatly reduces pumping losses. Studies have shown early intake valve closing reduces pumping losses by 40%, and increases fuel economy by 7%. It also reduced nitric oxide emissions by 24% at partial load conditions. A possible downside to early intake valve closing

2907-493: The scheme is that only a duration variation equal to that of the lobe nose true radius (in camshaft degrees or double this value in crankshaft degrees) is possible. In practice this type of variable cam has a maximum range of duration variation of about forty crankshaft degrees. This is the principle behind what seems to be the very first variable cam suggestion appearing in the USPTO patent files in 1925 (1527456). The "Clemson camshaft"

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2964-474: The system has subsequently been developed to improve economy and emissions, and has been introduced across Mitsubishi's range of vehicles, from the i kei car to the high-performance Lancer Evolution sedan to the Mirage/Space Star global economy car. Newest developments have led to MIVEC system being evolved into a continuous variable valve timing and also being the first VVT system to be used into

3021-435: The valve opening duration was referred to as "steam cut-off ”. The Stephenson valve gear , as used on early steam locomotives, supported variable cutoff , that is, changes to the time at which the admission of steam to the cylinders is cut off during the power stroke. Early approaches to variable cutoff coupled variations in admission cutoff with variations in exhaust cutoff. Admission and exhaust cutoff were decoupled with

3078-437: The valve slightly early, more exhaust gas remains in the cylinder which increases fuel efficiency. This allows for more efficient operation under all conditions. The main factor preventing this technology from wide use in production automobiles is the ability to produce a cost-effective means of controlling the valve timing under the conditions internal to an engine. An engine operating at 3000 revolutions per minute will rotate

3135-422: The valve timing. Therefore, the timing can be optimized to suit all engine speeds and conditions. The simplest form of VVT is cam-phasing , whereby the phase angle of the camshaft is rotated forwards or backwards relative to the crankshaft. Thus the valves open and close earlier or later; however, the camshaft lift and duration cannot be altered solely with a cam-phasing system. Achieving variable duration on

3192-446: Was also a carbureted model, with 97 PS (71 kW; 96 hp) at 6,000  rpm and 126 N⋅m (93 lb⋅ft) at 3,500 rpm. Applications The 4G92 displaces 1.6 L (1,597 cc). It first appeared in the late-1991 Japanese-spec Mirage RS and Super R in DOHC form. The 4G92 is basically a version of the 4G91 with the bore increased to 81 mm (3.19 in). In

3249-986: Was considered a non-useful "technological showpiece" as late as 2004 due to the system's weight penalty. Since then, motorcycles including VVT have included the 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. Variable valve timing has begun to trickle down to marine engines. Volvo Penta 's VVT marine engine uses

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