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Valve timing diagram for a 4-stroke engine. 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 ...
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.
The timing and lift profile of the valve opening events are controlled by the camshafts, through use of a carefully shaped lobe on a rotating shaft. The camshaft is driven by the crankshaft and, in the case of a four-stroke engine, rotates at half the speed of the crankshaft.
Many modern engines now use unconventional valve timing to produce the effect of a shorter compression stroke/longer power stroke. Miller applied this technique to the four-stroke engine, so it is sometimes referred as the Atkinson/ Miller cycle , US patent 2817322 dated Dec 24, 1957. [ 2 ]
The difference in displacement is achieved by variance in bore and stroke. [4] The 4B1 engine family is the first to have the continuously variable valve timing MIVEC system applied not only to its intake valves but also to its exhaust valves. The intake and exhaust cam timing is continuously independently controlled and provide four optimized ...
Scavenging is equally important for both two-stroke and four-stroke engines. Most modern four-stroke engines use crossflow cylinder heads and valve timing overlap to scavenge the cylinders. Modern two-stroke engines use either Schnuerle scavenging (also known as "loop scavenging") or uniflow scavenging.
Late intake valve closing (LIVC) The first variation of continuous variable valve timing involves holding the intake valve open slightly longer than a traditional engine. This results in the piston actually pushing air out of the cylinder and back into the intake manifold during the compression stroke.
Valves per cylinder 4 ; Variable valve timing Camshaft adjustment on both the inlet and outlet side; Displacement 3,982 cc (4.0 L; 243.0 cu in) Bore x stroke 83 mm × 92 mm (3.27 in × 3.62 in) Cylinder spacing 90 mm (3.54 in) Compression ratio 10.5:1