Choose Your Variable Valve Timing (VVT) Help Topic Below
Today, Variable Valve Timing (VVT); is the next step to enhance engine output.
As you know; valves activate the breathing of the engine. The timing of the breathing, is controlled by the shape and angle of camshafts. To optimize the breathing; engines require different valve timing, at different speeds.
When the (RPM) increases; the duration of intake and exhaust stroke decreases. This allows the fresh air to come in slower. In turn slowing down the exhaust air as well. Therefore, the best solution is to; open the inlet valves earlier; and close the exhaust valves later.
In other words; the Overlapping between intake period and exhaust period; should be increased as (RPM) increases.
Without (VVT) technology; engineers used to choose the best compromise timing. For example, a van may adopt less overlapping; for the benefits of low speed output. A racing engine may adopt considerable overlapping; for high speed power. An ordinary sedan; may adopt valve timing optimize for midrange speed. That way both the low speed drivability and high speed output will not be sacrificed. No matter which one; the result is just optimized for a particular speed.
With Variable Valve Timing (VVT); power and torque can be optimized; across a wider (RPM) band.
With (VVT) The most noticeable results are:
- The engine can rev higher; thus raises peak power.
- Low speed torque increases; thus improves drivability.
Moreover, all these benefits come without any drawback.
In some designs; valve lift can also be varied; according to engine speed. At high speed, higher lift quickens air intake and exhaust. As a result, further optimize the breathing with Variable Valve Timing (VVT). Of course, at lower speed such lift will generate counter effects. Consequently, deteriorating the mixing process of fuel and air. Consequently, decreasing output and leading to misfires. Therefore, the lift should be variable according to engine speed.
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