| How does Camshaft works? |
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A camshaft is a part which rotates in sync with the crankshaft. It's function is to cause the valves to open and close for each cylinder at the proper time to support the introduction of the air charge to each cylinder, support compression of the air charge, support combustion of the air charge, and exhaust of the air charge.
It has a lobe, or off concentric protrusion, for each valve. In our cars that is 12 lobes. On top of the lobes are the pushrods which move in concert with the lobes as the camshaft is rotated. This rotational motion of the cam is translated to "up and down" motion of the pushrod.
The other end of the pusrod contacts one side of the rocker arm. The rocker arm moves up and down as the pushrod pushes it. The other end on the rocker arm sits on top of the top end of the valve. As one end of the rocker arm moves the other end moves in the opposite direction like a seesaw. This causes the valve to open and close.
The valve springs push against the rocker arm and have a tendency to cause the valves to want to stay shut. It also helps the pushrod stay in
contact with the cam since it is always under tension.
Now....depending on how the cam is designed will determine when each
valve opens and shuts. Depending on the parameters choosen this will change the operating characteristics of the engine.
The cam is always a series of design compromises. What makes good HP changes where the engine makes that HP. What makes good torque may limit the peak HP of the engione.
Generally, duration is the amount of time the valve stays open during a
revolution(s) of the crankshaft. More duration - better peak HP; peaker HP curve and lower fuel economy and more loppy idle. This is a gross simplification since there are many varibles to camshaft design.
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