The present-day engines are considered an engineering miracle, which do more with less. One of the technologies that have made this possible is Variable Valve Timing, or VVT. The smart system is able to change the personality of an engine real-time so that it can be frugal in daily usage and can demand power when needed. We shall see how VVT manages to attain this excellent duality.
What Is Variable Valve Timing and How Does It Work
An engine is essentially a pump which pumps air. It has inhalation of air and fuel and exhalation of exhaust. This breathing process is controlled by the valves in the cylinder head which provide gates. Their introduction and conclusion points are decisive.
In standard engines, these events of the valves are predetermined. The camshaft fixes it and cannot be altered. This is a tradeoff - a design that is efficient at high engine speeds is inefficient at low speeds, and the reverse.
Variable Valve Timing does away with this trade off. The system is dynamically adjustable in the relationship between the crankshaft and the camshaft using a complicated hydraulic or electronic actuator. Simply, it can either hasten or slow down the opening and closing of the valves when the engine is in motion. This enables the computer on the engine to keep adjusting the valves operation to suit the driving conditions at the time so that the engine is always breathing as efficiently as possible.
Fuel Economy Benefits of VVT in Daily Driving
Most drivers feel the greatest effect in increased efficiency in their fuel consumption particularly in the stop and go city traffic. VVT plays a significant role in a number of ways.
VVT is capable of maximizing valve overlap at low engine speeds like when idle or when the acceleration is mild. This is the short duration over which the intake and the exhaust valves are open. Through a very close regulation of this overlap, the engine is able to minimize pumping losses the energy that is wasted by drawing air into the cylinder. This allows the engine to work less directly saving fuel.
Moreover, optimized valve timing enhances high stability of combustion at low RPM. This enables the engineers to provide more aggressive methods such as operation of a leaner air-fuel mixture during light loads, which will further optimize the fuel consumption. VVT is a fastidious control over the combustion process, that is, by making certain that the engine only inhales that much air required at a particular time, which results in the minimum amount of wasted air, and the maximum amount of fuel.
Performance Gains How VVT Optimizes Power Across RPM Range
Although it is economical at low speeds, VVT does indeed make an engine realize its potential when you need it. It addresses a traditional performance dilemma, how to have high end torque and high RPM horsepower with the same engine.
The engine must take deep quick breaths at high engine speed. In this case, VVT is able to regulate the opening and closing time of the intake valves. This enables increased air and fuel to be crammed into the cylinders during high RPM which is called volumetric efficiency. What comes out is a high increase in high-end horsepower which enables the engine to rev much easier and make more power.
On the other hand, to get high low-end and mid-range response, the system uses timing to maximize torque. It also improves the swirl of the mixture of air-fuel, by timing the valve events to lower the RPMs and guaranteeing more complete combustion the instant the driver releases the accelerator. This removes the preferable flat spot or lag that is experienced in older engines, offering a smooth, responsive and powerful pull throughout the rev range.