Variable Valve Timing Systems: Development Trends Among Japanese Automotive Manufacturers
Toyota increases availability of its Dual VVT-i; Nissan develops continuously variable lift system

  Reported below are the recent trends among Japanese automotive manufacturers with regard to their development efforts of the variable valve timing systems that are said to effectively enhance a petro-fueled engine's torque and output while reducing fuel consumption and exhaust gas emissions.

  There are two types of variable valve timing systems, one in which the valve opening and closing timing is controlled continuously (variable valve timing) and the other in which the amount of valve lift and the duration during which the valve stays open are controlled (variable lift system).

  The continuously variable valve timing systems are used in nearly three out of every four passenger cars that were sold in Japan in 2005 by Japanese automotive manufacturers. The variable lift systems are used by Honda in its main models powered by its VTEC engine, and are also used by Toyota, Fuji Heavy Industries and Mitsubishi Motors.

  Japanese automotive manufacturers are relying on varying ways to satisfy contradicting goals of higher engine performances and higher fuel efficiency along with cleaner emissions:

(Note) Variable valve timing system: Valve timing refers to the timing of opening and closing of the intake and exhaust valves. Since the desired valve timing varies by the engine revolution, load and other factors, a valve timing catered to a low speed range necessarily leads to lower power when the vehicle is running at high speed. Similarly, the valve timing set to a high speed range results in low torques or lack of idling stability when the vehicle is running at low speed. Variable valve timing is designed to optimize the valve timing according to the vehicle's running conditions. The variable valve lift also offers a similar control so that the engine runs in optimum condition at all times.

■Phases of variable valve system development among Japanese manufacturers of passenger cars

Continuously variable valve timing system	Intake	Already used widely by all manufacturers
	Intake + Exhaust (Dual)	Toyota (greater availability planned; electric VVT-i used in Lexus LS460 in the intake side), Nissan (to be incorporated in the new VQ engine for FR models), Mitsubishi (used in Outlander for Japanese markets), Fuji Heavy (used in turbocharged DOHC 2000cc engine)
Variable intake valve lift system		Toyota (VVTL-i), Honda (i-VTEC), Mitsubishi (used in Grandis, to be used in Outlander for North American markets), Fuji Heavy (used in DOHC 3000cc engine for Legacy and SOHC 2500cc for Outback)
Continuously variable intake valve lift system		Toyota (said to be in the midst of development), Nissan (VEL development announced), Honda (an evolved version of VTEC to be developed in 2007FY), Mitsubishi (being developed as a system for the next-generation MIVEC engine)

■Trends of variable valve system development among Japanese manufacturers of passenger cars

	Description
Toyota	In 2006 fall, Toyota will start selling (1) the new Lexus LS460 powered by the newly-developed V8 engine with an intake and exhaust Dual VVT-i (Toyota's first electric VVT is used in the intake side), and (2) the new Corolla carrying the new 1800cc power plant featuring the Dual VVT-i.   The Dual VVT-i is already used in the V6 engines that were introduced in 2003. Toyota reportedly plans to substantially increase its availability by 2010.   Toyota is said to be developing a continuously variable valve lift control system also.
	■Effects on fuel efficiency: 5% or more improvement achieved by the new Dual VVT-i 1800cc engine over the conventional model.
Nissan	Has developed a continuously variable valve operating angle and valve lift control system (VEL).   Has developed the VQ engine designed exclusively for the new V6 3500cc front-drive vehicles featuring an intake and exhaust VTC.
	■Effects on fuel efficiency: 7-13% improvement by the VEL.
Honda	Plans to develop the evolved version of the VTEC engine by the end of 2007FY featuring a continuously variable control of the valve lift, coupled with 13% improvement in fuel efficiency compared to that of the 2005MY i-VTEC engine.   The 1800cc engine for the new Civic put on the market in 2005 fall features a variable intake air volume control (evolved version of the i-VTEC engine) and achieved a 6% improvement in fuel efficiency (in standalone tests).
	■Effects on fuel efficiency: 13% improvement thanks to the evolved version of the VTEC engine; 6% improvement thanks to the variable intake air volume control compared to the previous 1700cc engine.
Mitsubishi	The Outlander put on sale in 2005 fall is powered by an engine that has a variable intake and exhaust valve timing system. A continuously variable control system that controls three elements (intake valve lift, duration of valve opening, and valve opening and closing timing) is being developed (exhibited at 2005 Tokyo Motor Show).
Mazda	A variable valve timing is featured in all passenger car engines other than minicars, RX-8 and the 2000cc engines on Premacy (among the minicars, the variable valve timing is featured in the natural intake engine used in the AZ Wagon).
Fuji	A variable valve lift system is used in the SOHC 2500cc engine on the Legacy after major remodeling in May 2006. Fuji plans to adopt variable valve timing also in the future.   A variable valve timing is featured in all DOHC engines including those for minicars. A variable valve lift system is already used in the DOHC 3000cc engine.
Suzuki	A variable valve timing mechanism is used in the 1300-1800cc M engine and engines for minicars including MR Wagon, Wagon R, etc (other than the turbocharged engines).
Daihatsu	A variable valve timing (DVVT) is used in all engines other than those for minicars and in nearly all engines for minicars (other than the turbocharged engines).

Sources: PR materials from each company, printed information distributed and displayed during the 2006 Automotive Engineering Exposition, etc.

(Note)

Each manufacturer has a proprietary name for their variable valve timing system: Toyota: VVT (Variable Valve Timing System), Nissan and Honda: VTC (Variable Timing Control), Mitsubishi Motors: MIVEC (Mitsubishi Innovative Valve timing Electronic Control System), Fuji Heavy Industries: AVCS (Active Valve Control System), Suzuki: VVT (Variable Valve Timing), Daihatsu: DVVT (Dynamic Variable Valve Timing).

■Toyota: Increasing availability of the Dual VVT-i engines

  Toyota has its continuously variable valve timing system in the gasoline-fueled engines for nearly all passenger cars and SUVs, from the V8 engine to the 1000cc 1KR-FE engine used in Vitz, Passo and Belta (other than the 2000cc twin-turbocharged models of the Caldina, and Land Cruiser Cygnus/100).

  The V6 2500cc, 3000cc, and 3500cc GR engines, used in Toyota cars starting with the Harrier first put on sale in February 2003, feature the Dual VVT-i system that offers continuously variable control of the exhaust valve timing, in addition to the conventional, similar control of the intake valves.

  In June 2006, Toyota announced that the company's gasoline-fueled engine and transmission renewal project, started with the introduction of the GR engines in 2003, would be completed by 2010. With a plan to substantially increase the availability of the Dual VVT-i, Toyota added that the company has developed a new inline, 4-cylinder 1800cc 2ZR-FE engine featuring the Dual VVT-i. The new engine is to be used in the new Corolla to be released for marketing in 2006 fall.

  Toyota will also make the Dual VVT-i available on the V8 4600cc to be used in the new Lexus LS460 slated for sale in 2006 fall, which will be the first Toyota car with an electric variable valve timing control of the intake valves (the conventional, hydraulic control is used in the exhaust valves).

  Toyota is said to be in the process of developing a continuously variable valve lift control system also.

  Toyota has introduced a variable valve lift control system (VVTL-i, in which the valve lift is switched between high and low speed ranges as needed) in the 1800cc 2ZZ-GE engine used on Corolla, Celica, Will VS, etc. As of July 2006, the VVTL-i is available with Corolla Fielder/Runx and Allex.

■Toyota Dual VVT-i: Available on the V8 engine for the new Lexus LS and the new 1800cc engine
■V8 engine for the new Lexus LS460

The Dual VVT-i will be available with the new V8 engine to be used in the new Lexus LS460 slated for marketing in 2006 fall. By introducing the electric VVT-i in the intake side for the first time among Toyota vehicles (the exhaust valves are controlled by the conventional hydraulic system), the company claims that more sophisticated valve control will be achieved directly after the engine start unlike the conventional hydraulic control that takes some time before the control takes effect.

■New, inline 4-cylinder 1800cc engine

Toyota will introduce advanced mechanisms, such as the Dual VVT-i, in the new 1800cc 2ZR-FE engine to be used starting with the new models being put on sale in 2006 fall, in an effort to attain enough fuel efficiency to reduce CO2 emissions and increase the cleanliness of the exhaust gas while ensuring enough torque to maintain dynamic performance for the car. Toyota's development targets include the maximum power output of 100kW (compared to 97kW from the current 1800cc 1ZZ-FE engine), the maximum torque of 175Nm (compared to 170Nm), and at least 5% higher fuel efficiency over the existing engine.

Sources: Toyota PR material dated June 13, 2006, etc

■Toyota: Availability of the Dual VVT-i
■Lexus brand

	Release timing	Engine	Displacement	Dual VVT-I(note)
GS430 GS350	August 2005	3UZ-FE 2GR-FSE	V8 4300cc V6 3500cc	Dual VVT-i
SC430	August 2005	3UZ-FE	V8 4300cc
IS350 IS250	September 2005	2GR-FSE 4GR-FSE	V6 3500cc V6 2500cc	Dual VVT-i Dual VVT-i

■Toyota brand

	Release timing	Engine	Displacement	Dual VVT-i (note)
Crown Majesta	July 2004	3UZ-FE	V8 4300cc
Crown Athlete	December 2003	2GR-FSE 4GR-FSE	V6 3500cc V6 2500cc	Dual VVT-i Dual VVT-i
Crown Royal	December 2003	3GR-FSE 4GR-FSE	V6 3000cc V6 2500cc	Dual VVT-i Dual VVT-i
Mark X	November 2004	3GR-FSE 4GR-FSE	V6 3000cc V6 2500cc	Dual VVT-i Dual VVT-i
Estima	January 2006	2GR-FE 2AZ-FE	V6 3500cc Inline-4 2400cc	Dual VVT-i
Harrier	February 2003	2GR-FE 2AZ-FE	V6 3500cc Inline-4 2400cc	Dual VVT-i

Source: Toyota's on-line catalogs as of early July 2006
(Note) Blanks under "Dual VVT-i" represent engines with VVT-i on the intake side only.

■Toyota engines with variable valve lift control (VVTL-i)

	Model	Engine	Displacement
Corolla Fielder	Z AEROTOURER	2ZZ-GE	Inline-4 1800cc
Corolla Runx	Z AEROTOURER
Allex	RS180

Source: Toyota's on-line catalogs as of early July 2006
(Note)	VVTL-i stands for Variable Valve Timing and Lift-intelligent, a continuously variable valve timing and lift mechanism. In addition to the VVT-i function, the mechanism controls the intake and exhaust efficiencies precisely by switching the valve lift between one for high engine revolutions and another for low.

■Nissan: Has developed a continuously variable valve operating angle and valve lift control system (VEL)

  Nissan is using its variable valve timing control on all passenger cars and SUV (registered vehicles) other than the coaches and certain sports models.

  In March 2006, Nissan announced that the company had developed, jointly with Hitachi, a continuously variable valve operating angle and valve lift control system (VEL: Variable Valve Event & Lift System), which was exhibited during the 2006 Automotive Engineering Exposition held in May. The company claims that the new system will lead to a 7-13% increase in fuel efficiency and a 1-9% increase in torque as the result of reduced intake and exhaust resistances.

  Nissan's PR material refers to a throttle valve but the system adjusts the intake amount mainly by the valve lift and Nissan will reportedly discontinue the throttle valve in due time. The new system will be put to commercial application in 2-3 years mainly in 2000cc and larger petro-fueled engines.

■Nissan: Has developed Variable Valve Event & Lift System (VEL)

	Description
Aim	Reduce intake and exhaust resistances that normally lead to loss of the engine's energy
Main features	(1) Improved fuel efficiency and engine torque: Intake resistance, associated with the smaller throttle opening during low power operation, is reduced substantially, thereby realizing higher fuel efficiency and engine torque.
	(2) Improved throttle response: Unlike the conventional intake volume control by means of the throttle valve, intake is controlled directly by the intake valve, thereby increasing the throttle response.
	(3) Reduced HC emissions: The intake flow rate is increased by reducing the valve lift to break fuel into smaller particles for complete combustion, thereby reducing HC emissions normally caused by imperfect combustion.
System configuration	Rotational movement of the driveshaft (corresponds to an ordinary camshaft) having an eccentric cam is transmitted to the output cam by means of a rocker arm and two types of link to push down the engine valve. The control shaft located on the driveshaft is turned by a DC motor to move the link's fulcrum, thereby changing the output cam movement, thus varying the valve lift continuously.
Effects	1-9% higher torque, 40% faster response, 7-13% higher fuel efficiency, and 50% less HC emissions.

Sources: Nissan exhibits during the 2006 Automotive Engineering Exposition, etc.

■Nissan adopts intake and exhaust VTC in new VQ engines for the FR models

  Nissan has developed the new VQ 3500cc engine for the FR models. The engine features an intake and exhaust VTC (Variable Timing Control) with an electromagnetic eVTC in the exhaust valve (conventional hydraulic type is used in the intake valve). The new engine will be used in the new Infiniti G35 sedan slated for release in the North American markets in November 2006.

■Hitachi: Announces mid- to long-range plans of its variable valve timing system

  Hitachi exhibited its mid- to long-range plans of its variable valve timing system at the 2006 Automotive Engineering Exposition. As far as the continuously variable valve operating angle and valve lift control system (VEL: Variable Valve Event & Lift System) is concerned, the company plans to discontinue the throttle valve by around 2008 when the system will evolve into an intake and exhaust VEL. Similarly, the VTC (Variable Timing Control) will change from the intake VTC to an intake and exhaust VTC, and eventually evolve into an electronically controlled VTC capable of functioning under low engine revolution and oil temperature.

■Hitachi's mid- to long-range plans for the variable valve system

	2005~2010	2010~2015
Continuously variable lift system (VEL)	Develop swing-arm type VEL	Develop intake and exhaust VEL
	Throttle-less design (Note 1)
Variable valve lift control in low and high speed ranges (VVL)	Idle cylinders VVL (Note 2)
Variable valve timing system (VTC)	Intake and exhaust VTC
	Electronically-controlled VTC (Note 3)

Sources: Hitachi exhibits during the 2006 Automotive Engineering Exposition
(Notes) 1.	VEL: Throttle valve will remain in use for some time but the main source of control will shift to the valve lift and the throttle valve may be out of use by around 2008.
2.	VVL: Valve lift control system at high and low speed ranges. Will remain in use in engines, along with the idle cylinder function, after popular introduction of the VEL.
3.	Electronically-controlled VTC: Operational at low engine revolution and oil temperature (200 rpm, 0°C) that are too low for the conventional hydraulic VTC.

Hitachi's mid- to long-range plans for evolution of the variable valve systems

■Honda: Introduces variable intake volume control in i-VTEC engines for Civic and Stream

  In 1989, Honda completed VTEC that changes the amount of valve opening according to the engine revolution range (low, high) and adopted the new system in the Integra. In 2000, Honda developed i-VTEC, a combination of the VTEC and the VTC (continuously variable valve timing control), which is now installed in engines with piston displacement of 1800cc or larger used in STEPWGN, Odyssey and a few other main makes.

  The 1800cc i-VTEC engine for the new Civic, put on sale in 2005, features a variable intake volume control that reduces the pumping loss by delaying the intake valve closing event and increasing the throttle valve opening when the car is running in low-load condition. This system contributes to a 6% improvement in fuel efficiency compared to the previous 1700cc engine.

  The variable intake volume control i-VTEC is also made available in the 1800cc and 2000cc engines for the Stream at the time of full remodeling in July 2006.

  In July 2005, Honda announced the company's goals for its fuel efficiency improvement efforts through the 2007FY. According to the announcement, Honda will complete an evolved version of the VTEC, capable of continuously varying both the intake valve timing and valve lift, which the company claims will lead to a 13% improvement in fuel efficiency.

■Honda: Evolved VTEC, capable of continuously varying both the intake valve timing and valve lift
■Adopts variable intake volume control in the i-VTEC engines for the new Civic and the new Stream

Honda features variable intake volume control with a delayed closing cam in the i-VTEC engine for the new Civic put on sale in September 2005. By optimum control of the throttle valve by means of DBW (drive by wire), in addition to the valve control by means of a delayed closing cam (cam for delaying the closing timing of the intake valve), the new system contributes to up to 16% reduction of the pumping loss associated with the air intake, and 6% improvement in fuel efficiency (standalone testing of the engine) compared to the previous 1700cc engine. As a result, the new Civic registers fuel efficiency of 17.0km/L (5AT model) and 16.2km/L (5MT model).

The variable intake volume control i-VTEC engines are also used in the new Stream out on sale in July 2006. The 1800cc engine features a variable-length intake manifold that offers an optimum intake air inertia effect while the 2000cc engine has a three-stage variable-length intake manifold that offers full of torque in all ranges. Both engines register the fuel efficiency of 14.8km/L.

■Evolved VTEC gives continuously variable control of the valve timing and valve lift

The evolved VTEC, which Honda plans to introduce toward the end of the 2007FY, is characterized by intake volume control based on continuously variable control of the intake valve timing and the valve lift. The system will drastically reduce the pumping loss arising in the throttle valve, thereby achieving a 13% improvement in fuel efficiency compared to the ordinary i-VTEC engines available in 2005.

Sources: Honda PR materials dated July 13, 2006, July 20, 2005, July 5, 2005, etc

(Note)

Honda's VTEC system (variable valve timing and lift mechanism) features two types of rocker arms that are used to push the valve down so as to regulate the intake valve timing and lift in two stages, one for high speed range and the other for the low (first used with Integra in 1989). The i-VTEC system is a combination of the VTEC and VTC (Variable Timing Control) which, as far as the intake valve timing is concerned, offers continuously variable control of the timing according to the engine revolution and load (first featured in Stream in 2000).

■Mitsubishi Motors: Intake and exhaust continuously variable valve timing control featured in the Outlander engines

  Mitsubishi Motors uses MIVEC (Mitsubishi Innovative Valve timing Electronic Control system; a generic term of Mitsubishi Motors' engines with a variable valve timing control) in the engines for Colt/Colt Plus, Outlander, Grandis, and Lancer Evolution IX. The same system is also used in "i" which is a new minicar put on sale in January 2006.

  The SOHC 2400cc MIVEC engine used in Grandis and the SOHC 3000cc engines used in the Outlander for North American markets and exhibited at the New York Auto Show 2006 also feature a variable lift mechanism.

  The engine for the Outlander, put on sale in 2005 fall, features a system that offers continuously variable control of both the intake and exhaust valves.

■Mitsubishi Motors: Dual continuously variable valve timing used in the Outlander engine

The DOHC 2400cc engine for Mitsubishi Motors' new Outlander put on sale in 2005 fall features a variable valve timing control that continuously controls the timing of both the intake and exhaust valves. The system allows a more detailed control according to the engine revolution and load and, according to the company, realizes high performance and fuel efficiency that rivals the best in its class.

The intake cam phase is shifted continuously to any angle up to 40° and the exhaust cam phase up to 35° so as to control the valve timing according to the vehicle's running conditions: (1) low-speed and low-load condition: idling combustion is stabilized without overlapping; (2) normal condition: pumping loss is reduced by larger overlapping and high expansion ratio is secured by delaying the exhaust valve opening event in the combustion stroke; (3) low engine revolution and high-load condition: enough air is secured by early closing of the intake valve and high expansion ratio is secured by delaying the exhaust valve opening event, etc.

Sources: Mitsubishi Motors website

■Continuously variable valve timing and valve lift control system

  Mitsubishi Motors is in the process of developing a continuously variable valve timing and lift control system for the SOHC 2400cc engine. The system, called the next-generation MIVEC, was exhibited at the Tokyo Motor Show 2005.

■Mitsubishi Motors: Continuously variable valve timing and lift control system

Mitsubishi Motors is in the process of developing a next-generation of MIVEC, capable of continuously controlling three elements from a single mechanism (intake valve lift, period during which the valve remains open, and the valve opening and closing timing). The system was exhibited at the Tokyo Motor Show 2005.

The system being developed drastically reduces the pumping loss by regulating the amount of intake air by means of substantially changing the valve closing timing while the valve opening timing remains virtually unchanged. The system is based on the SOHC engine which, the company claims, will lead to low cost and compact design as a whole.

Sources: Mitsubishi Motors displays at the Tokyo Motor Show 2005

■Fuji Heavy Industries: Variable valve lift featured in the 2500cc engine for the Outback

  Fuji Heavy Industries has adopted a variable valve timing system, AVCS (Active Valve Control System), in most of its DOHC engines, including the engines for minicars. The DOHC 2000cc engine for the Legacy features an intake and exhaust DUAL AVCS. The company is said to have plans to adopt the AVCS in SOHC engines as well.

  The DOHC 3000cc has a variable valve lift mechanism (Direct Variable Valve Lift). The company adopted its first variable valve lift system, i-AVLS (i-Active Valve Lift System), in the SOHC 2500cc engine in the Legacy Outback at the time of major change in May 2006.

■Fuji Heavy Industries; Variable valve lift system in SOHC 2500cc engine for Outback

Fuji Heavy Industries adopted a variable valve lift system, i-AVLS (i-Active Valve Lift System), in the opposing SOHC 4-cylinder 2500cc engine in the Legacy Outback at the time of major change in May 2006. This system changes the amount of lift of one of the two intake valves according to the engine revolution (low-mid and mid-high ranges).

While in low-mid range, one of the intake valves is put in low-lift mode so that the generated swirl increases the velocity of intake air flow thereby improving the admixture fill-up and combustion efficiencies. This also improves exhaust gas performance. While in mid-high range, both intake valves are put in high-lift mode simultaneously so as to increase power.

Fuji Heavy Industries has for some time been using a variable intake valve timing system (AVCS) and variable intake valve lift system (DVVL: Direct Variable Valve Lift) in the opposing 6-cylinder DOHC 3000cc engines for the Legacy series.

Sources: Fuji Heavy Industries PR material dated May 24, 2006, Legacy catalog.

■Fuji Heavy Industries: Availability of variable intake valve timing system (AVCS) and Direct Variable Valve Lift system (DVVL) in Legacy engines

	DOHC			SOHC
	3000cc	2000cc turbocharged	2000cc	2500cc	2000cc
Variable valve timing system	AVCS	Dual AVCS	AVCS
Variable valve lift system	DVVL			i-AVLS

Source: Legacy catalog
(Note)	The AVCS is also available in Fuji Heavy Industries' DOHC engines for Forester, Impreza and minicars (other than the supercharged models).

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