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The lobe separation angle (LSA, also called lobe centreline angle) is the angle between the centreline of the intake lobes and the centreline of the exhaust lobes. [23] A higher LSA reduces overlap, which improves idle quality and intake vacuum, [22] however using a wider LSA to compensate for excessive duration can reduce power and torque ...
The cam can be seen as a device that converts rotational motion to reciprocating (or sometimes oscillating) motion. [clarification needed] [3] A common example is the camshaft of an automobile, which takes the rotary motion of the engine and converts it into the reciprocating motion necessary to operate the intake and exhaust valves of the cylinders.
Oil under constant pressure is supplied to the lifter via an oil channel, through a small hole in the lifter body. When the engine valve is closed (lifter in a neutral position), the lifter is free to fill with oil. As the camshaft lobe enters the lift phase of its travel, it compresses the lifter piston, and a valve shuts the oil inlet.
In an overhead valve engine the tappets (on right) are sandwiched between pushrods and the camshaft. In an internal combustion engine, a tappet (also called a 'valve lifter' or 'cam follower') [3] [4] [5] is the component which converts the rotation of the camshaft into vertical motion to open and close an intake or exhaust valve.
The mechanism is a coaxial shaft arrangement where the outer shaft carries the main body of the cam lobe. The main body of the cam lobe is in its maximum duration form. Typically the main lobe body would have a duration of about 450°. The lobe is very long axially, about 45 mm (1.8 in), and its profile consists of conventional opening and ...
The ratio is determined by the ratio of the distances from the rocker arm's pivot point to the point where it touches the valve and the point where it touches the pushrod/camshaft. A rocker ratio greater than one essentially increases the camshaft's lift. Current automotive design favors rocker arm ratios of about 1.5:1 to 1.8:1.
Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft (located in the engine block) to the valves (located in the cylinder head). The bottom end of a pushrod is fitted with a lifter, upon which the camshaft makes contact. The camshaft lobe moves the lifter upwards, which moves the ...
The cam's shape determines the piston's stroke length, timing, and speed. These factors directly influence the engine's performance characteristics. In a cam engine, the cam is connected to a drive mechanism, usually a shaft. This shaft rotates the cam at a specific speed. The rotation of the cam is synchronized with the engine's combustion cycle.