Well Greg… sounds pretty obvious… the timing of a valve varies?… Yep, it’s true but why?
Many car companies today are utilizing some type of V.V.T. systems. The reason they do is to squeeze better performance from a smaller engine over a wider variation of conditions.
Think of it sort of like the way your body increases blood flow and respiration when you are exercising. Your body adjusts to varying demands on it.
The camshaft can be considered “brain” of an internal combustion engine. It determines when a intake or exhaust valve opens in the combustion cycle (timing), how far open it will go (called lift), how long it will stay open (called duration). The cam is important to control how much air and exhaust can pass through the engine at a given speed. And, with every machine design, there are compromises. When the cam is made for maximum power (high lift and long duration), the engine suffers at low speeds, light throttle and idle. When the cam is made for smooth idle and low speed operation, the amount of maximum power suffers.
Most vehicles that we work on use some sort of computer controlled, hydraulically actuated (by engine oil pressure) system to adjust the timing of the camshaft to allow for the best of both worlds.
Without getting into the minutia of how this is accomplished on each different engine, let’s just say that it works…very well! Word to the wise… since these systems depend on engine oil pressure, keeping your engine oil clean is critical to the function of these systems, as well as the longevity of the engine.
For more detail, just ask and one of our resident geeks will talk your ear off.
“My VTEC kicked in, yo!”