VTEC
Encyclopedia
VTEC is a valvetrain
system developed by Honda
to improve the volumetric efficiency of a four-stroke internal combustion engine
. The VTEC system uses two camshaft profiles and electronically selects between the profiles. It was invented by Honda R&D engineer Ikuo Kajitani, and was the first system of its kind. Different types of variable valve timing
and lift control systems have also been produced by other manufacturers (MIVEC from Mitsubishi, AVCS
from Subaru
, VVT-i/VVTL-i
from Toyota, VarioCam Plus from Porsche
, NeoVVL from Nissan, etc.).
Japan
levies a tax based on engine displacement, and Japanese auto manufacturers have correspondingly focused their R&D efforts toward improving the performance of smaller engine designs through means other than displacement increases. One method for increasing performance into a static displacement includes forced induction
, as with models such as the Toyota Supra
and Nissan 300ZX
which used turbocharger
applications and the Toyota MR2
which used a supercharger
for some model years. Another approach is an unconventional engine design, such as the rotary engine
used in the Mazda RX-7
and RX-8
. A third option is to change the cam timing profile, of which Honda VTEC was the first successful commercial design for altering the profile in real-time.
The VTEC system provides the engine with multiple camshaft profiles optimized for both low and high RPM operations. In basic form, the single cam profile of a conventional engine is replaced with two profiles: one optimized for low-RPM stability and fuel efficiency, and the other designed to maximize high-RPM power output. The switching operation between the two cam lobes is controlled by the ECU which takes account of engine oil pressure, engine temperature, vehicle speed, engine speed and throttle position. Using these inputs, the ECU is programmed to switch from the low lift to the high lift cam lobes when the conditions mean that engine output will be improved. At the switch point a solenoid is actuated which allows oil pressure from a spool valve to operate a locking pin which binds the high RPM cam follower to the low RPM ones. From this point on, the poppet valve
opens and closes according to the high-lift profile, which opens the valve further and for a longer time. The switch-over point is variable, between a minimum and maximum point, and is determined by engine load. The switch-down back from high to low RPM cams is set to occur at a lower engine speed than the switch-up (representing a hysteresis
cycle) to avoid a situation in which the engine is asked to operate continuously at or around the switch-over point.
The older approach to timing adjustments is to produce a camshaft with a valve timing
profile that is better suited to high-RPM operation. The improvements in high-RPM performance occur in trade for a power and efficiency loss at lower RPM ranges, which is where most street-driven automobiles operate a majority of the time. Correspondingly, VTEC attempts to combine high-RPM performance with low-RPM stability.
, which used a 3 litre DOHC VTEC V6 with 280 bhp. DOHC VTEC engines soon appeared in other vehicles, such as the 1992 Acura Integra GS-R (B17A1 1.7 litre engine), and later in the 1992 Honda Prelude
VTEC (H22A 2.2 litre engine with 195 hp) and Honda Del Sol VTEC (B16A2 1.6 litre engine). The Integra Type R (1997–2001) available in the Japanese market produces 200 bhp using a B18C5 1.8 litre engine. Honda has also continued to develop other varieties and today offers several varieties of VTEC, such as i-VTEC and i-VTEC Hybrid.
However, beginning with the J37A4 3.7L, SOHC V6 engine introduced on all 2009 Acura TL SH-AWD models, SOHC VTEC was incorporated for use with intake and exhaust valves. The intake and exhaust rocker shafts contain primary and secondary intake and exhaust rocker arms, respectively. The primary rocker arm contains the VTEC switching piston, while the secondary rocker arm contains the return spring. The term "primary" does not refer to which rocker arm forces the valve down during low-RPM engine operation. Rather, it refers to the rocker arm which contains the VTEC switching piston and receives oil from the rocker shaft.
The primary exhaust rocker arm contacts a low-profile camshaft lobe during low-RPM engine operation. Once VTEC engagement occurs, the oil pressure flowing from the exhaust rocker shaft into the primary exhaust rocker arm forces the VTEC switching piston into the secondary exhaust rocker arm, thus locking both exhaust rocker arms together. The high-profile camshaft lobe which normally contacts the secondary exhaust rocker arm alone during low-RPM engine operation is able to move both exhaust rocker arms together which are locked as a unit.
The secondary intake rocker arm contacts a low-profile camshaft lobe during low-RPM engine operation. Once VTEC engagement occurs, the oil pressure flowing from the intake rocker shaft into the primary intake rocker arm forces the VTEC switching piston into the secondary intake rocker arm, thus locking both intake rocker arms together. The high-profile camshaft lobe which normally contacts the primary intake rocker alone during low-RPM engine operation is able to move both intake rocker arms together which are locked as a unit.
The difficulty of incorporating VTEC for both the intake and exhaust valves in a SOHC engine has been removed on the J37A4 by a novel design of the intake rocker arm. Each exhaust valve on the J37A4 corresponds to one primary and one secondary exhaust rocker arm. Therefore, there are a total of twelve primary exhaust rocker arms and twelve secondary exhaust rocker arms.
However, each secondary intake rocker arm is shaped similar to a "Y" which allows it to contact two intake valves at once. One primary intake rocker arm corresponds to each secondary intake rocker arm. As a result of this design, there are only six primary intake rocker arms and six secondary intake rocker arms.
in the cylinder and thus allowing a leaner mixture to be used. As the engine's speed increases, both valves are needed to supply sufficient mixture. A sliding pin, which is pressured by oil, as in the regular VTEC, is used to connect both valves together and allows the full opening of the second valve. The engine runs at normal performance using the second cam position that would typically be tuned for high-RPM performance in other two-stage VTEC designs.
four cylinder engine family in 2001 (2002 in the U.S.).
In the United States, Honda first debuted the technology on the 2002 Honda CR-V.
VTC controls the timing of valve lift and the timing of valve duration are still limited to distinct low- and high-RPM profiles, but the timing of the intake camshaft is now capable of advancing between 25 and 50 degrees (depending upon engine configuration) during operation. The timing of the VTC intake camshaft phasing changes are implemented by a computer controlled, oil driven adjustable cam gear. Phasing is determined by a combination of engine load and rpm, ranging from fully retarded at idle to somewhat advanced at full throttle and low RPM. The effect is further optimization of torque output, especially at low and midrange RPM. There are two types of i-VTEC K series engines which are explained in the next paragraph.
Type S or the Civic Si
and the other is for economy motors found in the CR-V
or Accord
. The performance i-VTEC system is basically the same as the DOHC VTEC system of the B16A's; both intake and exhaust have 3 cam lobes per cylinder. However the valvetrain has the added benefit of roller rockers and continuously variable intake cam timing. Performance i-VTEC is a combination of conventional DOHC VTEC with VTC.
The economy i-VTEC is more like the SOHC VTEC-E in that the intake cam has only two lobes, one very small and one larger, as well as no VTEC on the exhaust cam. The two types of motor are easily distinguishable by the factory rated power output: the performance motors make around 200 hp or more in stock form and the economy motors do not make much more than 160 hp from the factory.
) that includes Honda's cylinder deactivation technology which closes the valves on one bank of (3) cylinders during light load and low speed (below 80 km/h (49.7 mph)) operation. According to Honda "VCM technology works on the principle that a vehicle only requires a fraction of its power output at cruising speeds. The system electronically deactivates cylinders to reduce fuel consumption. The engine is able to run on 3,4, or all 6 cylinders based on the power requirement. Essentially getting the best of both worlds. V6 power when accelerating or climbing, as well as the efficiency of a smaller engine when cruising." The technology was originally introduced to the US on the Honda Odyssey
minivan, and can now be found on the Honda Accord Hybrid, the 2006 Honda Pilot, and the 2008 Honda Accord. Example: EPA estimates for the 2011 (271hp SOHC 3.5L) V6 Accord are 24mpg combined vs. 27 in the two 4 cylinder equipped models.
i-VTEC VCM was also used in 1.3L 4-cylinder engines used in Honda Civic Hybrid.
It was first used in 2003 Honda Stream
.
Although it was speculated that it would first be used in 2008 Honda Accord, the vehicle instead utilizes the existing i-VTEC system.
A related US patent (6,968,819) was filed in 2005-01-05.
occurred with the introduction of Honda's VFR800
sportbike in 2002. Similar to the SOHC VTEC-E style, one intake valve remains closed until a threshold of 7000 rpm is reached, then the second valve is opened by an oil-pressure actuated pin. The dwell of the valves remains unchanged, as in the automobile VTEC-E, and little extra power is produced but with a smoothing-out of the torque curve. Critics maintain that VTEC adds little to the VFR experience while increasing the engine's complexity. Honda seemed to agree as their VFR1200, a model announced in October 2009, came to replace the VFR800; which abandons the V-TEC concept in favour of a large capacity narrow-vee "unicam" (i.e. sohc) motor.
Valvetrain
Valvetrain is an all-encompassing term used to describe the mechanisms and parts which control the operation of the valves. A traditional reciprocating internal combustion engine uses valves to control air and fuel flow into and out of the cylinders, facilitating combustion.-Layout:Valvetrain: The...
system developed by Honda
Honda
is a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...
to improve the volumetric efficiency of a four-stroke internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
. The VTEC system uses two camshaft profiles and electronically selects between the profiles. It was invented by Honda R&D engineer Ikuo Kajitani, and was the first system of its kind. Different types of variable valve timing
Variable valve timing
In internal combustion engines, variable valve timing , also known as Variable valve actuation , is a generalized term used to describe any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine...
and lift control systems have also been produced by other manufacturers (MIVEC from Mitsubishi, AVCS
Active Valve Control System
Active Valve Control System is an automobile variable valve timing technology used by Subaru. It varies the timing of the intake valves by using hydraulic oil pressure to rotate the camshaft in order to provide optimal air flow in and out of the engine...
from Subaru
Subaru
; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...
, VVT-i/VVTL-i
VVT-i
VVT-i, or Variable Valve Timing with intelligence, is an automobile variable valve timing technology developed by Toyota, similar in performance to the BMW's VANOS. The Toyota VVT-i system replaces the Toyota VVT offered starting in 24 December 1991 on the 5-valve per cylinder 4A-GE engine. The...
from Toyota, VarioCam Plus from Porsche
Porsche
Porsche Automobil Holding SE, usually shortened to Porsche SE a Societas Europaea or European Public Company, is a German based holding company with investments in the automotive industry....
, NeoVVL from Nissan, etc.).
Context, and description
VTEC was initially designed to increase the power output of an engine to 100 HP/litre or more while maintaining practicality for use in mass production vehicles. Some later variations of the system were designed solely to provide improvements in fuel efficiency.Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
levies a tax based on engine displacement, and Japanese auto manufacturers have correspondingly focused their R&D efforts toward improving the performance of smaller engine designs through means other than displacement increases. One method for increasing performance into a static displacement includes forced induction
Forced induction
Forced induction is the process of compressing air on the intake of an internal combustion engine . A forced induction engine uses a gas compressor to increase the pressure, temperature and density of the air...
, as with models such as the Toyota Supra
Toyota Supra
The Toyota Supra is a sports car/grand tourer that was produced by Toyota Motor Company from 1979 to 2002. The styling of the Toyota Supra was derived from the Toyota Celica, but it was both longer and wider. Starting in mid-1986, the Supra became its own model and was no longer based on the Celica...
and Nissan 300ZX
Nissan 300ZX
The Z31 chassis designation was first introduced in 1983 as a 1984 Nissan/Datsun 300ZX in the US only. The 300ZX, as its predecessors, was known as a Nissan in other parts of the world. This continued in the US until 1985 model year when Nissan standardized their brand name worldwide and dropped...
which used turbocharger
Turbocharger
A turbocharger, or turbo , from the Greek "τύρβη" is a centrifugal compressor powered by a turbine that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine , thereby resulting in greater performance...
applications and the Toyota MR2
Toyota MR2
The Toyota MR2 is a two-seat, mid-engined, rear wheel drive sports car produced by Central Motors, a part of Toyota, from 1984 until July 2007 when production stopped in Japan...
which used a supercharger
Supercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
for some model years. Another approach is an unconventional engine design, such as the rotary engine
Wankel engine
The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle takes place in a space between the inside of an oval-like epitrochoid-shaped housing and a rotor that...
used in the Mazda RX-7
Mazda RX-7
Series 1 is commonly referred to as the "SA22C" from the first alphanumerics of the vehicle identification number. This series of RX-7 had exposed steel bumpers and a high-mounted indentation-located license plate, called by Werner Buhrer of Road & Track magazine a "Baroque depression."In 1980...
and RX-8
Mazda RX-8
The Mazda RX-8 is a sports car manufactured by Mazda Motor Corporation. It first appeared in 2001 at the North American International Auto Show. It is the successor to the RX-7 and, like its predecessors in the RX range, it is powered by a Wankel engine. The RX-8 began North American sales in the...
. A third option is to change the cam timing profile, of which Honda VTEC was the first successful commercial design for altering the profile in real-time.
The VTEC system provides the engine with multiple camshaft profiles optimized for both low and high RPM operations. In basic form, the single cam profile of a conventional engine is replaced with two profiles: one optimized for low-RPM stability and fuel efficiency, and the other designed to maximize high-RPM power output. The switching operation between the two cam lobes is controlled by the ECU which takes account of engine oil pressure, engine temperature, vehicle speed, engine speed and throttle position. Using these inputs, the ECU is programmed to switch from the low lift to the high lift cam lobes when the conditions mean that engine output will be improved. At the switch point a solenoid is actuated which allows oil pressure from a spool valve to operate a locking pin which binds the high RPM cam follower to the low RPM ones. From this point on, the poppet valve
Poppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
opens and closes according to the high-lift profile, which opens the valve further and for a longer time. The switch-over point is variable, between a minimum and maximum point, and is determined by engine load. The switch-down back from high to low RPM cams is set to occur at a lower engine speed than the switch-up (representing a hysteresis
Hysteresis
Hysteresis is the dependence of a system not just on its current environment but also on its past. This dependence arises because the system can be in more than one internal state. To predict its future evolution, either its internal state or its history must be known. If a given input alternately...
cycle) to avoid a situation in which the engine is asked to operate continuously at or around the switch-over point.
The older approach to timing adjustments is to produce a camshaft with a valve timing
Valve timing
In a piston engine, the valve timing is the precise timing of the opening and closing of the valves.In four-stroke cycle engines and some two-stroke cycle engines, the valve timing is controlled by the camshaft. It can be varied by modifying the camshaft, or it can be varied during engine operation...
profile that is better suited to high-RPM operation. The improvements in high-RPM performance occur in trade for a power and efficiency loss at lower RPM ranges, which is where most street-driven automobiles operate a majority of the time. Correspondingly, VTEC attempts to combine high-RPM performance with low-RPM stability.
History
VTEC, the original Honda variable valve control system, originated from REV (Revolution-modulated valve control) introduced on the CBR400 in 1983 known as HYPER VTEC. In the regular four-stroke automobile engine, the intake and exhaust valves are actuated by lobes on a camshaft. The shape of the lobes determines the timing, lift and duration of each valve. Timing refers to an angle measurement of when a valve is opened or closed with respect to the piston position (BTDC or ATDC). Lift refers to how much the valve is opened. Duration refers to how long the valve is kept open. Due to the behavior of the working fluid (air and fuel mixture) before and after combustion, which have physical limitations on their flow, as well as their interaction with the ignition spark, the optimal valve timing, lift and duration settings under low RPM engine operations are very different from those under high RPM. Optimal low RPM valve timing, lift and duration settings would result in insufficient filling of the cylinder with fuel and air at high RPM, thus greatly limiting engine power output. Conversely, optimal high RPM valve timing, lift and duration settings would result in very rough low RPM operation and difficult idling. The ideal engine would have fully variable valve timing, lift and duration, in which the valves would always open at exactly the right point, lift high enough and stay open just the right amount of time for the engine speed in use.DOHC VTEC
Introduced as a DOHC system in Japan in the 1989 Honda Integra XSi and the Honda CR-X SiR, which both used the 160 bhp B16A engine. The same year, Europe saw the arrival of VTEC in the Honda CRX 1.6i-VT, using a 150 bhp variant (B16A1). The US market saw the first VTEC system with the introduction of the 1991 Honda NSXHonda NSX
The Honda NSX, or Acura NSX, is a sports car that was produced between 1990 and 2005 by the Japanese automaker Honda. It is equipped with a mid-engine, rear-wheel drive layout, powered by an all-aluminium V6 gasoline engine featuring Honda's Variable Valve Timing and Lift Electronic Control ...
, which used a 3 litre DOHC VTEC V6 with 280 bhp. DOHC VTEC engines soon appeared in other vehicles, such as the 1992 Acura Integra GS-R (B17A1 1.7 litre engine), and later in the 1992 Honda Prelude
Honda Prelude
The Honda Prelude was a sports coupe produced by Japanese automaker Honda from 1978 until 2001. It replaced the Honda S800, a front-engined, front wheel drive sports car...
VTEC (H22A 2.2 litre engine with 195 hp) and Honda Del Sol VTEC (B16A2 1.6 litre engine). The Integra Type R (1997–2001) available in the Japanese market produces 200 bhp using a B18C5 1.8 litre engine. Honda has also continued to develop other varieties and today offers several varieties of VTEC, such as i-VTEC and i-VTEC Hybrid.
SOHC VTEC
As popularity and marketing value of the VTEC system grew, Honda applied the system to SOHC (Single Over Head Cam) engines, which share a common camshaft for both intake and exhaust valves. The trade-off was that Honda's SOHC engines only benefitted from the VTEC mechanism on the intake valves. This is because VTEC requires a third center rocker arm and cam lobe (for each intake and exhaust side), and in the SOHC engine, the spark plugs are situated between the two exhaust rocker arms, leaving no room for the VTEC rocker arm. Additionally, the center lobe on lized by either the intake or the exhaust, limiting the VTEC feature to one side.However, beginning with the J37A4 3.7L, SOHC V6 engine introduced on all 2009 Acura TL SH-AWD models, SOHC VTEC was incorporated for use with intake and exhaust valves. The intake and exhaust rocker shafts contain primary and secondary intake and exhaust rocker arms, respectively. The primary rocker arm contains the VTEC switching piston, while the secondary rocker arm contains the return spring. The term "primary" does not refer to which rocker arm forces the valve down during low-RPM engine operation. Rather, it refers to the rocker arm which contains the VTEC switching piston and receives oil from the rocker shaft.
The primary exhaust rocker arm contacts a low-profile camshaft lobe during low-RPM engine operation. Once VTEC engagement occurs, the oil pressure flowing from the exhaust rocker shaft into the primary exhaust rocker arm forces the VTEC switching piston into the secondary exhaust rocker arm, thus locking both exhaust rocker arms together. The high-profile camshaft lobe which normally contacts the secondary exhaust rocker arm alone during low-RPM engine operation is able to move both exhaust rocker arms together which are locked as a unit.
The secondary intake rocker arm contacts a low-profile camshaft lobe during low-RPM engine operation. Once VTEC engagement occurs, the oil pressure flowing from the intake rocker shaft into the primary intake rocker arm forces the VTEC switching piston into the secondary intake rocker arm, thus locking both intake rocker arms together. The high-profile camshaft lobe which normally contacts the primary intake rocker alone during low-RPM engine operation is able to move both intake rocker arms together which are locked as a unit.
The difficulty of incorporating VTEC for both the intake and exhaust valves in a SOHC engine has been removed on the J37A4 by a novel design of the intake rocker arm. Each exhaust valve on the J37A4 corresponds to one primary and one secondary exhaust rocker arm. Therefore, there are a total of twelve primary exhaust rocker arms and twelve secondary exhaust rocker arms.
However, each secondary intake rocker arm is shaped similar to a "Y" which allows it to contact two intake valves at once. One primary intake rocker arm corresponds to each secondary intake rocker arm. As a result of this design, there are only six primary intake rocker arms and six secondary intake rocker arms.
VTEC-E
VTEC-E is a variation of SOHC VTEC which was used to increase efficiency at low RPM. At low RPM, one of the two intake valves is only allowed to open a very small amount, increasing the fuel/air atomizationAtomization
Atomization or Atomizer may refer to:* The conversion of a vaporized sample into atomic components in atomic spectroscopy* An apparatus using an atomizer nozzle* Atomizer Geyser, a cone geyser in Yellowstone National Park...
in the cylinder and thus allowing a leaner mixture to be used. As the engine's speed increases, both valves are needed to supply sufficient mixture. A sliding pin, which is pressured by oil, as in the regular VTEC, is used to connect both valves together and allows the full opening of the second valve. The engine runs at normal performance using the second cam position that would typically be tuned for high-RPM performance in other two-stage VTEC designs.
3-Stage VTEC
3-Stage VTEC is a version that employs 3 different cam profiles to control intake valve timing and lift. Due to this version of VTEC being designed around a SOHC valve head, space was limited and so VTEC can only modify the opening and closing of the intake valves. The low-end fuel economy improvements of VTEC-E and the performance of conventional VTEC are combined in this application. From idle to 2500-3000RPM, depending on load conditions, one intake valve fully opens while the other opens just slightly, enough to prevent pooling of fuel behind the valve, also called 12 valve mode. This 12 Valve mode results in swirl of the intake charge which increases combustion efficiency resulting in improved low end torque and better fuel economy. At 3000-5400 RPM, depending on load, one of the VTEC solenoids engages which causes the 2nd valve to lock onto the first valve's camshaft lobe. Also called 4 valve mode, this method resembles a normal engine operating mode and improves the mid-range power curve. At 5500-7000 RPM, the second VTEC solenoid engages (both solenoids now engaged) so that both intake valves are using a middle, third camshaft lobe. The third lobe is tuned for high performance and provides peak power at the top end of the RPM range.i-VTEC
(intelligent-VTEC) has VTC (Variable Valve Timing Control) introduced continuously variable timing of camshaft phasing on the intake camshaft of DOHC VTEC engines. The technology first appeared on Honda's K-seriesHonda K engine
The Honda K series engine is a four-cylinder four-stroke engine introduced in 2001. The K series engines are equipped with DOHC valvetrains and use roller rockers to reduce friction. The engines use a coil-on-plug, distributorless ignition system with a coil for each spark plug...
four cylinder engine family in 2001 (2002 in the U.S.).
In the United States, Honda first debuted the technology on the 2002 Honda CR-V.
VTC controls the timing of valve lift and the timing of valve duration are still limited to distinct low- and high-RPM profiles, but the timing of the intake camshaft is now capable of advancing between 25 and 50 degrees (depending upon engine configuration) during operation. The timing of the VTC intake camshaft phasing changes are implemented by a computer controlled, oil driven adjustable cam gear. Phasing is determined by a combination of engine load and rpm, ranging from fully retarded at idle to somewhat advanced at full throttle and low RPM. The effect is further optimization of torque output, especially at low and midrange RPM. There are two types of i-VTEC K series engines which are explained in the next paragraph.
K-series
The K-Series motors have two different types of i-VTEC systems implemented. The first is for the performance motors like in the RSXAcura RSX
The Honda Integra DC5 is a Japanese performance sports car, which was also known as the Acura RSX in North America . It is available in base and "Type-S" models in North America, and a "Integra iS / Integra Type S" and "Type R" version sold in Japan and Oceania...
Type S or the Civic Si
Honda Civic Si
The Honda Civic Si is a sport compact / hot hatch version of the Civic built by the Japanese automaker Honda. The Si trim, which stands for "Sport Injected," was introduced for the third generation of Honda Civics in both Japan and North America...
and the other is for economy motors found in the CR-V
Honda CR-V
The Honda CR-V is a compact suv, now called crossover, manufactured since 1995 by Honda. It was loosely derived from the Honda Civic to satisfy a public demand for a sport-utility vehicle from Honda. There are discrepancies as to what "CR-V" stands for, with Honda sources in different markets...
or Accord
Honda Accord
The Honda Accord is a series of compact, mid-size and full-size automobiles manufactured by Honda since 1976, and sold in a majority of automotive markets throughout the world....
. The performance i-VTEC system is basically the same as the DOHC VTEC system of the B16A's; both intake and exhaust have 3 cam lobes per cylinder. However the valvetrain has the added benefit of roller rockers and continuously variable intake cam timing. Performance i-VTEC is a combination of conventional DOHC VTEC with VTC.
The economy i-VTEC is more like the SOHC VTEC-E in that the intake cam has only two lobes, one very small and one larger, as well as no VTEC on the exhaust cam. The two types of motor are easily distinguishable by the factory rated power output: the performance motors make around 200 hp or more in stock form and the economy motors do not make much more than 160 hp from the factory.
i-VTEC with Variable Cylinder Management (VCM)
In 2003, Honda introduced an i-VTEC V6 (an update of the J-seriesHonda J engine
The J-series was Honda's second V6 engine family, introduced in 1996. It is a 60° V6 – Honda's existing C-series was a 90° engine. The J-series was designed for transverse mounting. It has a shorter bore spacing , shorter connecting rods, and a special smaller crankshaft than the C-series for...
) that includes Honda's cylinder deactivation technology which closes the valves on one bank of (3) cylinders during light load and low speed (below 80 km/h (49.7 mph)) operation. According to Honda "VCM technology works on the principle that a vehicle only requires a fraction of its power output at cruising speeds. The system electronically deactivates cylinders to reduce fuel consumption. The engine is able to run on 3,4, or all 6 cylinders based on the power requirement. Essentially getting the best of both worlds. V6 power when accelerating or climbing, as well as the efficiency of a smaller engine when cruising." The technology was originally introduced to the US on the Honda Odyssey
Honda Odyssey
Honda Odyssey can refer to three motor vehicles manufactured by Honda:* Honda Odyssey , a minivan sold in Japan and other parts of the world* Honda Odyssey , a minivan sold primarily in the United States and Canada...
minivan, and can now be found on the Honda Accord Hybrid, the 2006 Honda Pilot, and the 2008 Honda Accord. Example: EPA estimates for the 2011 (271hp SOHC 3.5L) V6 Accord are 24mpg combined vs. 27 in the two 4 cylinder equipped models.
i-VTEC VCM was also used in 1.3L 4-cylinder engines used in Honda Civic Hybrid.
i-VTEC i
It is a version of i-VTEC with direct injection.It was first used in 2003 Honda Stream
Honda Stream
The Honda Stream is a compact MPV manufactured by the Japanese automaker Honda since 2001. Japanese models have gasoline direct injection 1.7 L and 2.0 L engines with improved fuel efficiency...
.
AVTEC
The AVTEC (Advanced VTEC) engine was first announced in 2006. It combines continuously variable valve lift and timing control with continuously variable phase control. Honda originally planned to produce vehicles with AVTEC engines within next 3 years.Although it was speculated that it would first be used in 2008 Honda Accord, the vehicle instead utilizes the existing i-VTEC system.
A related US patent (6,968,819) was filed in 2005-01-05.
VTEC in motorcycles
Apart from the Japanese market-only Honda CB400SF Super Four HYPER VTEC, introduced in 1999, the first worldwide implementation of VTEC technology in a motorcycleMotorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
occurred with the introduction of Honda's VFR800
Honda VFR800
The Honda VFR800, also known as the Interceptor, is a motorcycle introduced by Honda in 1998. It is a successor to the VFR750F , which was preceded by the VF750.From its first sales in 1986, the VFR750F scored highly on many press reviews...
sportbike in 2002. Similar to the SOHC VTEC-E style, one intake valve remains closed until a threshold of 7000 rpm is reached, then the second valve is opened by an oil-pressure actuated pin. The dwell of the valves remains unchanged, as in the automobile VTEC-E, and little extra power is produced but with a smoothing-out of the torque curve. Critics maintain that VTEC adds little to the VFR experience while increasing the engine's complexity. Honda seemed to agree as their VFR1200, a model announced in October 2009, came to replace the VFR800; which abandons the V-TEC concept in favour of a large capacity narrow-vee "unicam" (i.e. sohc) motor.
External links
- Honda tech pages: VTEC, i-VTEC DOHC, S2000 2.0L DOHC VTEC, Type-R 2.0L DOHC i-VTEC, 2.0L DOHC i-VTEC I, V6 3.0L i-VTEC, V6 3.5L VTEC
- Honda Technology Picture Book, VTEC
- Paul Tan : Honda's i-VTEC I Direct Injection Engine
- Temple of VTEC Asia Special Feature : The Basic VTEC Mechanism
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- Animation of how VTEC works on YouTube
- World Honda: New i-VTEC Technology