Variable Valve Timing (VVT) Explained

Variable Valve Timing (VVT) is a term that you often hear when talking about modern engines. To understand what it does and why manufacturers use it, we first need to talk about fuel and air.

Every internal combustion engine needs fuel and air to produce power. In very simple terms, the more it gets, the more power it can produce. The way in which an engine manages these two inputs dictates how powerful, efficient, and smooth it is.

This is where Variable Valve Timing (VVT) comes into play. It’s a technology that allows an engine to make the most of the air it takes in. In this article, we discuss this system in detail, from its origins right up to modern-day technology.

What Is Variable Valve Timing (VVT)

VVT is a technology that adjusts cam timing to change:

• Valve Timing
• Valve Duration
• Valve Lift

Variable Valve Timing is a system used in internal combustion engines to adjust the operation of the valves. This is done by altering the camshaft profile, either mechanically, hydraulically, or electronically.

Changing the camshaft profile allows the valve opening duration, lift, and timing to be adjusted throughout the rev range. The result is an optimal air mixture across a broader engine operating range.

What Are The Benefits Of VVT?

• Better power and torque over a broader rev range
• Higher peak power and torque outputs
• Improved fuel economy
• Lower emissions

Allowing the engine to breathe better makes it more efficient. This results in more power over a wider rev range and lower fuel consumption, too.

How Has The VVT System Evolved?

Like any technology, VVT has evolved over the decades. Automotive VVT milestones of note include:

• 1903-1979: Cadillac, Porsche, and Fiat all experimented with VVT designs, but none made it to series production.
• 1980: Alfa Romeo Spider 2000 gets mechanical VVT system
• 1983: VVT upgraded to an electronic version for the Alfa Spider
• 1987: Nissan introduces NVTCS (Nissan Valve Timing Control System). Electronically controlled valve timing only.
• 1989: Honda introduces the VTEC system. Camshaft phasing allowed for two distinct camshaft profiles for low and high rev situations. This allowed for both valve timing and lift to be adjusted.
• 1992: Porsche releases VarioCam on its 4-cylinder 968 models. First VVT system to offer continuous adjustment of valves. Initially, only altered intake valve timing.
• 1992: BMW offers VANOS on certain 3 and 5 Series models. Initially offering continuous adjustment of the intake valve timing.
• 2000s-onwards: VVT technology becomes more mainstream.

The earliest use of VVT in production vehicles was by Alfa Romeo on its 1980 Spider 2000 models. Like most early VVT systems, it was a mechanical design that only adjusted the timing of the intake valves.

Newer systems introduced electronic management and control of both the intake and exhaust valves. BMW’s VANOS and Porsche’s VarioCam were the first to offer continuous adjustment across a broader rev range. Honda used a simple but effective dual-cam profile system that delivered big power at high revs, while maintaining drivability at lower engine speeds.

While VVT was a relative anomaly in the ‘90s and even the early 2000s, just about every modern engine has some form of valve control. Since then, Honda, BMW, and Porsche have evolved their VVT system to work with modern direct injection and turbocharged engines. Chrysler introduced dual VVT to its lineup when it launched its ‘World Engine’ range in 2006. Today, most auto manufacturers have their own Variable Valve Control Systems.

Which Manufacturers Offer VVT Systems?

Most auto enthusiasts will associate Variable Valve Timing with Honda and its iconic VTEC system. And while it was fun to experience those screaming high-revving early VTEC systems, they certainly weren’t the only manufacturer to offer this technology. Honda just marketed their VVT system better than anyone else.

Nowadays, you would struggle to find an engine that doesn’t have VVT. Each manufacturer has either developed or licensed valve timing technology to work with their engines and uses its own acronym.

VVT Acronyms

Whatever the name, the end result of VVT is a more efficient engine that produces more power and torque across a wider operating range. You may recognize these other names or acronyms, depending on your vehicle make and model:

• BMW – Variable Nockenwellensteuerung (VANOS)
• Chrysler, General Motors – Variable Valve Timing (VVT)
• Ford – Twin Independent Variable Camshaft Timing (Ti-VCT)
• Nissan – Continuous Variable Valve Timing Control System (CVVCTS)
• Subaru – Active Valve Control System (AVCS)
• Toyota, Lexus – Variable Valve Timing with Intelligence (VVT-i)

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