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VarioCam is an automobile variable valve timing technology developed by Porsche. VarioCam varies the timing of the intake valves by adjusting the tension on the timing chain connecting the intake and exhaust camshafts. VarioCam was first used on the 1992 3.0 L engine in the Porsche 968.
Four-stroke cycle used in gasoline/petrol engines: intake (1), compression (2), power (3), and exhaust (4). The right blue side is the intake port and the left brown side is the exhaust port. The cylinder wall is a thin sleeve surrounding the piston head which creates a space for the combustion of fuel and the genesis of mechanical energy.
Variable valve lift (VVL) is an automotive piston engine technology which varies the height a valve opens in order to improve performance, fuel economy or emissions. There are two main types of VVL: discrete, which employs fixed valve lift amounts, and continuous, which is able to vary the amount of lift.
A possible downside to early intake valve closing is that it significantly lowers the temperature of the combustion chamber, which can increase hydrocarbon emissions. [3] Early intake valve opening Early intake valve opening is another variation that has significant potential to reduce emissions. In a traditional engine, a process called valve ...
With traditional fixed valve timing, an engine will have a period of "valve overlap" at the end of the exhaust stroke, when both the intake and exhaust valves are open. The intake valve is opened before the exhaust gases have completely left the cylinder, and their considerable velocity assists in drawing in the fresh charge. Engine designers ...
Under low-speed, high load, MIVEC ensures optimal torque delivery with the intake valve closing timing advanced to ensure sufficient air volume. At the same time, the exhaust valve opening timing is retarded to provide a higher expansion ratio and improved efficiency. At idle, valve overlap is eliminated to stabilize combustion.
A pair of poppet valves bent by collision with a piston after timing belt failure. The engine was running at 4500 RPM. In interference engine designs, replacing a timing belt in regular intervals (manufacturers recommend intervals ranging from 60,000 to 104,000 miles) or repairing chain issues as soon as they are discovered is essential, as incorrect timing may result in the pistons and valves ...
The induction stroke is the first phase in a four-stroke (e.g. Otto cycle or Diesel cycle) engine.It involves the downward movement of the piston, creating a partial vacuum that draws an air-fuel mixture (or air alone, in the case of a direct injection engine) into the combustion chamber.