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  • Timing belt (camshaft)


    Timing belt A timing belt, timing chain, or cambelt is a part of an internal combustion engine that synchronizes the rotation of the crankshaft and the camshaft(s) so that the engine's valves open and close at the proper times during each cylinder's intake and exhaust strokes. In an interference engine the timing belt or chain is also critical to preventing the piston from striking the valves. A timing belt is usually a toothed belt—a drive belt with teeth on the inside surface. A timing chain is a roller chain. Cosworth BDR engine, with timing belt and pulleys Many modern production automobile engines use a timing belt to synchronize crankshaft and camshaft rotation; some engines, particularly cam in block designs, used gears to drive the camshaft, but this was rare for OHC designs. The use of a timing belt or chain instead of gear drive enables engine designers to place the camshaft(s) further from the crankshaft, and in engines with multiple camshafts a timing belt or chain also enables the camshafts to be placed further from each other.

  • Camshaft


    Computer animation of a camshaft operating valves A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.

  • Ignition timing


    Pressure in cylinder pattern in dependence on ignition timing: (a) - misfire, (b) too soon, (c) optimal, (d) too late. In a spark ignition internal combustion engine, Ignition timing refers to the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke. The need for advancing (or retarding) the timing of the spark is because fuel does not completely burn the instant the spark fires, the combustion gases take a period of time to expand and the angular or rotational speed of the engine can lengthen or shorten the time frame in which the burning and expansion should occur. In a vast majority of cases, the angle will be described as a certain angle advanced before top dead center (BTDC). Advancing the spark BTDC means that the spark is energized prior to the point where the combustion chamber reaches its minimum size, since the purpose of the power stroke in the engine is to force the combustion chamber to expand. Sparks occurring after top dead center (ATDC) are usually counter-productive (producing wasted spark, back-fire, engine knock, etc.

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