Variable Valve Timing and Variable Valve Lift session

In internal combustion engines, variable valve timing, often abbreviated to VVT, is a generic term for an automobile piston engine technology. VVT allows the lift, duration or timing (some or all) of the intake or exhaust valves (or both) to be changed while the engine is in operation.

Most of the VVT technology designed to achieve better fuel consumption and better power output while some are designed solely to achieve ultimate peak power. Before we start, it is history lessons now.

Fiat was the first auto manufacturer to patent a functional automotive variable valve timing system which included variable lift.

Honda's REV motorcycle engine employed on the Japanese market-only Honda CBR400F in 1983 provided a technology base for VTEC.

In 1986, Nissan developed their own form of VVT with the VG30DE(TT) engine for their Mid-4 Concept. Nissan chose to focus their NVCS (Nissan Valve-Timing Control System) mainly on torque production at low to medium engine speeds, because, the vast majority of the time, automobile engines will not be operated at extremely high speeds.

The next step was taken in 1989 by Honda with the VTEC system. Honda had started production of a system that gives an engine the ability to operate on two completely different cam profiles, eliminating a major compromise in engine design. One profile designed to operate the valves at low engine speeds provides good road manners, low fuel consumption and low emissions output. The second is a high lift, long duration profile and comes into operation at high engine speeds to provide an increase in power output. The VTEC system was also further developed to provide other functions in engines designed primarily for low fuel consumption. The first VTEC engine Honda produced was the B16A which was installed in the Integra, CRX, and Civic hatchback available in Japan and Europe. In 1991 the Acura NSX powered by the C30A became the first VTEC equipped vehicle available in the US. VTEC can be considered the first "cam switching" system and is also one of only a few currently in production.

And then, we have all sorts of technology today such as from BMW Vanos, Toyota VVT-i etc etc…

Below here we start to list some examples that is common in our region. First and foremost, we will start with the biggest hits that sparked the flame, the ever “torqueless wonder” VTEC system by Honda.

• VTEC (Variable Valve Timing and lift Electronic Control)It varies duration, timing and lift by switching between two different sets of cam lobes.
• i-VTEC (Intelligent VTEC) Simply add continuous intake cam phasing (timing) to high-output DOHC 4 cylinder engines, such as the K20A than traditional VTEC, such as B16A. i-VTEC does not necessarily have two sets of cam lobes like traditional VTEC. In economy oriented SOHC and DOHC 4 cylinder engines such as L15A, R18A, and K20Z2 the i-VTEC system increases engine efficiency by delaying the closure of the intake valves under certain conditions and by using an electronically controlled throttle valve to reduce pumping loss. In SOHC V6 engines the i-VTEC system is used to provide Variable Cylinder Management (VCM) which deactivates one bank of 3 cylinders during low demand operation.
• VTEC-E, unlike most VTEC systems VTEC-E is not a cam switching system, instead it uses the VTEC mechanism to allow for a lean intake charge to be used by closing one intake valve under certain conditions, also called as 12v-16v system.
• A-VTEC (Advanced VTEC) Latest from Honda, continuously varies the valve timing and valve lifting.

Next comes the ever ever Toyota.

• VVT (Variable Valve Timing) Toyota 4A-GE 20-Valve engine introduced VVT in the 1992 Corolla GT-versions, also featuring in the ever famous and best Toyota Levin AE86.
• VVT-i (Variable Valve Timing Intelligent) Continuously varies the timing of the intake camshaft, or both the intake and exhaust camshafts, features in most of the Toyota’s production lineup.
• VVTL-i (Variable Valve Timing and Lift Intelligent)Continuously varies the timing of the intake valves. Varies duration, timing and lift of the intake and exhaust valves by switching between two different sets of cam lobes. Such application is similar to Honda’s i-VTEC. Example such as the 2ZZ-GE 1.8 litre engine that powers Toyota Celica, also serve as the engine for the Lotus Exige S.
• Valvematic is the latest technology by Toyota. Same as A-VTEC, it varies valve timing and valve lift continuously.

Next is the Mitsubishi.

• MIVEC (Mitsubishi Innovative Valve timing Electronic Control) Varies valve timing, duration and lift by switching between two different sets of cam lobes. However the latest 4B1 engine series uses a different variant of MIVEC which varies timing of both intake and exhaust camshafts continuously.

Now here comes our national P1, Proton.

• Campro (Cam Profile) Varies valve lift, and half done engine by Proton, which later completed with the CPS. Campro can be fitted either with CPS and VIM, or IAFM.
• Campro CPS (Cam Profile Switching) with VIM (Variable Intake Manifold) Varies valve lift by using 2 different cam profiles, one for low lift and one for high lift, similar to VTEC and MIVEC. Just that instead of using rocker arm to switch between 2 cams, it uses direct tappets with locking pins. VIM switches between long intake manifolds for normal cruising and short intake manifolds for high speed cruising.
• Campro IAFM (Integrated Air Fuel Module) Just a simple variable length air intake gimmick.

Followed by our national P2, Perodua.

• DVVT (Dynamic Variable Valve Timing) Essentially it is a Toyota’s VVT-i, just without the refinement. Toyota owns Daihatsu, and Daihatsu supports Perodua.

Now for some western, BMW.

• Valvetronic - Provides continuously variable lift for the intake valves; used in conjunction with Double VANOS.
• VANOS (Variable Nockenwellen Steuerung) Varies intake timing by rotating the camshaft in relation to the gear.
• Double VANOS - Continuously varies the timing of the intake and exhaust valves.

Back to Toyota’s higher level, Lexus.

• VVT-iE (Variable Valve Timing Intelligent by Electric motor)Continuously varies the intake camshaft timing using an electric actuator.

Going to Mazda.

• S-VT (Sequential Valve Timing) Continually varies intake timing and crank angle using an oil control valve actuated by the ECU to control oil pressure.

The very “swift” Suzuki.

• VVT (Variable Valve Timing) Same as Toyota.

The Inokom and Hyundai.

• CVVT (Continuously Variable Valve Timing) Same as Toyota VVT-i.

Sky in the line Nissan.

• N-VCT (Nissan Variable Cam Timing) Varies the rotation of the cam only, does not alter lift or duration of the valves.
• VVL (Nissan Ecology Oriented Variable Valve Lift and Timing) Varies timing, duration, and lift of the intake and exhaust valves by using two different sets of cam lobes.
• CVTC (Continuously Variable Timing Control) Similar to N-VCT, just continuously variable.
• VVEL (Variable Valve Event and Lift) A rocker arm and two types of links close the intake-valves by transferring the rotational movement of a drive shaft with an eccentric cam to the output cam. The movement of the output cam is varied by rotating the control shaft within the DC motor and changing the fulcrums of the links. This makes a continuous adjustment of the valve lift amount possible. C-VTC and VVEL together control the valve phases and its valve events and lifts, allowing free-control of the valve timing and lift. It performs similarly to BMW's Valvetronic system but with less parts operates to a higher engine speed (RPM), other similar systems are offered from Honda (A-VTEC) and Toyota (Valvematic).

The king of the automobile industry, Porsche.

• VarioCam - Varies intake timing by adjusting tension of a cam chain.
• VarioCam Plus - Varies intake valve timing by rotating the cam in relation to the cam sprocket as well as duration, timing and lift of the intake and exhaust valves by switching between two different sets of cam lobes.

Finally, we end here with some videos.