|
|
VVT - Variable Valve Timing
Who said that one has to sacrifice power on the altar of fuel efficiency? Questions like these motivate engineers to go beyond the realms of existing technological constraints and develop new benchmark technologies. VVT or Variable Valve Timing is one such technological innovation in today’s gasoline engines.
At a simplistic level it endows the engine with a unique ability to change the timing of opening & closing of the valves. Engine with VVT technology can independently vary the opening & closing of the valves, resulting in greater control over the combustion process, which translates into improved performance.
Vtec from Honda, for all practical purposes assumed to have innovated this technology. Vtec consists of tow unique cams one each for inlet and exhaust respectively. Different manufacturers over time has used variation of this basis theme of varying valve timing and developed their pnw versions of this technology.
How does it work?
The working principle of this tech is similar to the energy requirements of every human being. Quantum of energy required by us changes with the kind of work one had to perform or is performing. Higher energy is required under rigorous working conditions and lesser when we are performing normal duties.
Engines are no different. The amount of load on it is not uniform throughout their span of its working. Engines experiences higher load while going up vs while moving on a flat surface, likewise, load on the engine varies with number of passengers in the car at a given time.
VVT technology is designed to sense these variations and change valve opening and closing timing in accordance with the load conditions. The technology alters valve time to ensure that optimum amount of fuel and air is released in the cylinder according to the load conditions.
VARIATIONS OF THE VALVES
• Late Intake Valve Closing: VVT keeps the intake open slightly longer than the traditional engine technology, as a result high pressure air is pushed back into the intake manifold. So on that the same can be pushed back into the cylinder in subsequent intake cycle.
• Early Intake Valve Closing: Most suited for low load conditions thus reducing pumping losses, by closing the intake valve is closed midway between in its stroke. This is done because low load conditions require lower amount of air/fuel. Thus improving fuel efficiencies and also reducing NO emissions.
• Early Intake Valve Opening: Means some exhaust can flow can flow out of the cylinder into the intake manifold. The same after cooling down in the intake manifold is pumped back into the cylinder in its next cycle. This variation significantly reduces the emission of the vehicle.
• Early/Late Exhaust Valve Closing: By early closing of exhaust valve, more exhaust gases remain inside which can be used to increase the fuel-efficiency. By closing the valves late, more air-fuel mixture can be put into the combustion chamber.
Thus VVT combines the efficiency & performance in optimal way. It not only enhances the performance aspect but also take care of the fuel-efficiency. This helps you to enjoy the performance without compromising the fuel efficiency.
|