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A cylinder with longitudinal draft Profile view of a drafted cylinder with the draft dimension. In engineering, draft is the amount of taper for molded or cast parts perpendicular to the parting line. It can be measured in degrees or mm/mm (in/in). Consider the fabrication of a hollow plastic box, without lid.
Absolute cylinder pressure is used to calculate the dynamic compression ratio, using the following formula: = where is a polytropic value for the ratio of specific heats for the combustion gases at the temperatures present (this compensates for the temperature rise caused by compression, as well as heat lost to the cylinder)
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 is 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.
VR5 and VR6 engines are very compact and light, having a narrow V angle which allows a single cylinder block and cylinder head. These engines use a single cylinder head so are technically a straight engine with the name "VR" coming from the combination of German words “Verkürzt” and “Reihenmotor” meaning “shortened inline engine”.
In a multi-cylinder engine, pistons may reach top dead centre simultaneously or at different times depending on the engine configuration. For example: In the V-twin configuration, the two pistons reach TDC at different times, equal to the angular displacement between the cylinders.
The pitch surface of a gear is the imaginary toothless surface that you would have by averaging out the peaks and valleys of the individual teeth. The pitch surface of an ordinary gear is the shape of a cylinder. The pitch angle of a gear is the angle between the face of the pitch surface and the axis.
In an engine designed to use the squish effect, at top dead centre the piston crown comes very close (typically less than 1 mm [2]) to the cylinder head. The gases are suddenly "squished" out within the combustion chamber , creating turbulence which promotes thorough air-fuel mixing, a factor beneficial to efficient combustion .
The volume ratio / is called the "isentropic expansion ratio". (For the Otto cycle is the same as the compression ratio V 1 / V 2 {\displaystyle V_{1}/V_{2}} ). Mechanically this is the expansion of the hot gaseous mixture in the cylinder known as expansion (power) stroke.