MIVEC on:
[Wikipedia]
[Google]
[Amazon]
MIVEC (Mitsubishi Innovative Valve timing Electronic Control system) is the
MIVEC (Mitsubishi Innovative Valve timing Electronic Control system) is the brand name
A brand is a name, term, design, symbol or any other feature that distinguishes one seller's good or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create an ...
of a variable valve timing
In internal combustion engines, variable valve timing (VVT) is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with var ...
(VVT) engine
An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.
Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...
technology developed by Mitsubishi Motors
is a Japanese multinational automobile manufacturer headquartered in Minato, Tokyo, Japan.4G92'' powerplant, a 1,597 cc naturally aspirated
, Mitsubishi Motors North America press release 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, 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 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 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 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 a brief period, boosting torque. From the '' 4B1'' engine family onward, MIVEC has evolved into a
, Mitsubishi Motors North America press release 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: *Under most conditions, to ensure highest fuel efficiency, valve overlap is increased to reduce pumping losses. The exhaust valve opening timing is retarded for higher expansion ratio, enhancing fuel economy. *When maximum power is demanded (high engine speed and load), intake valve closing timing is retarded to synchronize the intake air pulsations for larger air volume. *Under low-speed, high load, MIVEC ensures optimal torque delivery with the intake valve closing timing advanced to ensure sufficient air volume. At the same time, the exhaust valve opening timing is retarded to provide a higher expansion ratio and improved efficiency. *At idle, valve overlap is eliminated to stabilize combustion. Mitsubishi's '' 4N1'' engine family is the world's first to feature a
, Mitsubishi Motors South Africa website a form of
DOHC
An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion c ...
16 valve straight-4
A straight-four engine (also called an inline-four) is a four-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.
The vast majority of automotive four-cylinder engines use a straight-four layout (with the ...
. 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
The Mitsubishi Mirage is a range of cars produced by the Japanese manufacturer Mitsubishi from 1978 until 2003 and again since 2012. The hatchback models produced between 1978 and 2003 were classified as subcompact cars, while the sedan and s ...
hatchback
A hatchback is a car body configuration with a rear door that swings upward to provide access to a cargo area. Hatchbacks may feature fold-down second row seating, where the interior can be reconfigured to prioritize passenger or cargo volume. ...
and the Mitsubishi Lancer
The Mitsubishi Lancer is an automobile produced by the Japanese manufacturer Mitsubishi Motors since 1973.
The Lancer has been marketed as the Colt Lancer, Dodge Colt, Plymouth Colt, Chrysler Valiant Lancer, Chrysler Lancer, Eagle Summit, Hin ...
sedan. While the conventional ''4G92'' engine provided at 7000 rpm
Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines.
Standards
ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
, the MIVEC-equipped engine could achieve at 7500 rpm. Similar improvements were seen when the technology was applied to the 1994 Mitsubishi FTO
The Mitsubishi FTO is a front engined, front-wheel drive coupe produced by Mitsubishi Motors between 1994 and 2000. It was originally planned to be exclusively for the Japanese domestic market, although its popularity as a grey market import to th ...
, whose top-spec GPX variant had a '' 6A12'' 1997 cc DOHC
An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion c ...
24 valve V6 with peak power of at 7500 rpm. The GR model, whose otherwise identical powerplant was not MIVEC-equipped, produced at 7000 rpm by comparison.
Although initially designed to enhance performance, the system has subsequently been developed to improve economy
An economy is an area of the production, distribution and trade, as well as consumption of goods and services. In general, it is defined as a social domain that emphasize the practices, discourses, and material expressions associated with the ...
and emissions, and has been introduced across Mitsubishi's range of vehicles, from the i kei car
Kei car (or , kanji: , "light automobile", ), known variously outside Japan as Japanese city car or Japanese microcar, is the Japanese vehicle category for the smallest highway-legal passenger cars with restricted dimensions and engine capacit ...
to the high-performance Lancer Evolution
The Mitsubishi Lancer Evolution, popularly referred to as the 'Evo', is a sports sedan and rally car based on the Lancer that was manufactured by Japanese manufacturer Mitsubishi Motors from 1992 until 2016. There have been ten official versi ...
sedan to the Mirage/Space Star global economy car.
Newest developments have led to MIVEC system being evolved into a continuous variable valve timing
Continuity or continuous may refer to:
Mathematics
* Continuity (mathematics), the opposing concept to discreteness; common examples include
** Continuous probability distribution or random variable in probability and statistics
** Continuous g ...
and also being the first VVT system to be used into a passenger car diesel engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...
.
Operation
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 the MIVEC system is altering the cam profiles and thus tailoring engine performance in response to driver input."2007 Mitsubishi Outlander Debuts New-Generation V-6 Engine And Segment-Exclusive Six-Speed Sportronic(R) Transmission", Mitsubishi Motors North America press release 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, 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 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 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 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 a brief period, boosting torque. From the '' 4B1'' engine family onward, MIVEC has evolved into a
continuous variable valve timing
Continuity or continuous may refer to:
Mathematics
* Continuity (mathematics), the opposing concept to discreteness; common examples include
** Continuous probability distribution or random variable in probability and statistics
** Continuous g ...
(CVVT) system (dual VVT on intake and exhaust valves)."All-New 2008 Mitsubishi Lancer Delivers Driven-To-Thrill Performance from New 152-HP Engine and Optional CVT", Mitsubishi Motors North America press release 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: *Under most conditions, to ensure highest fuel efficiency, valve overlap is increased to reduce pumping losses. The exhaust valve opening timing is retarded for higher expansion ratio, enhancing fuel economy. *When maximum power is demanded (high engine speed and load), intake valve closing timing is retarded to synchronize the intake air pulsations for larger air volume. *Under low-speed, high load, MIVEC ensures optimal torque delivery with the intake valve closing timing advanced to ensure sufficient air volume. At the same time, the exhaust valve opening timing is retarded to provide a higher expansion ratio and improved efficiency. *At idle, valve overlap is eliminated to stabilize combustion. Mitsubishi's '' 4N1'' engine family is the world's first to feature a
variable valve timing
In internal combustion engines, variable valve timing (VVT) is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with var ...
system applied to passenger car diesel engines.Mitsubishi Motors UK Geneva motor show 2010 presskit
MIVEC-MD
In the early years of developing its MIVEC technology, Mitsubishi also introduced a variant dubbed MIVEC-MD (Modulated Displacement),"Mitsubishi Motors History - Engine Technology", Mitsubishi Motors South Africa website a form of
variable displacement Variable displacement is an automobile engine technology that allows the engine displacement to change, usually by deactivating cylinders, for improved fuel economy. The technology is primarily used in large, multi-cylinder engines. Many automobil ...
. Under a light throttle load, the intake and exhaust valves in two of the cylinders would remain closed, and the reduced pumping losses gave a claimed 10–20 percent improvement in fuel economy. Modulated Displacement was dropped around 1996.
Current implementations
Past implementations
Footnotes
{{Mitsubishi Motors technologies Variable valve timing Mitsubishi Motors technologies