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An engine is described as oversquare or short-stroke if its cylinders have a greater bore diameter than its stroke length, giving a bore/stroke ratio greater than 1:1. An oversquare engine allows for more and larger valves in the head of the cylinder, higher possible rpm by lowering maximum piston speed, and lower crank stress due to the lower ...
Consumption map of a 1.5-litre three-cylinder diesel engineA consumption map or efficiency map [1] is a chart that displays the brake-specific fuel consumption of an internal combustion engine at a given rotational speed and mean effective pressure, in grams per kilowatt-hour (g/kWh).
BSFC numbers change a lot for different engine designs, and compression ratio and power rating. Engines of different classes like diesels and gasoline engines will have very different BSFC numbers, ranging from less than 200 g/(kW⋅h) (diesel at low speed and high torque) to more than 1,000 g/(kW⋅h) (turboprop at low power level).
The amount of power generated by a piston engine is related to its size (cylinder volume), whether it is a two-stroke engine or four-stroke design, volumetric efficiency, losses, air-to-fuel ratio, the calorific value of the fuel, oxygen content of the air and speed . The speed is ultimately limited by material strength and lubrication.
The stroke ratio, determined by dividing the bore by the stroke, traditionally indicated whether an engine was designed for power at high engine speeds or torque at lower engine speeds. [ 2 ] [ 3 ] The term "bore" can also be applied to the bore of a locomotive cylinder or steam engine pistons .
For example, if the static compression ratio is 10:1, and the dynamic compression ratio is 7.5:1, a useful value for cylinder pressure would be 7.5 1.3 × atmospheric pressure, or 13.7 bar (relative to atmospheric pressure). The two corrections for dynamic compression ratio affect cylinder pressure in opposite directions, but not in equal strength.
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A gasoline engine burns a mix of gasoline and air, consisting of a range of about twelve to eighteen parts (by weight) of air to one part of fuel (by weight). A mixture with a 14.7:1 air/fuel ratio is stoichiometric, that is when burned, 100% of the fuel and the oxygen are consumed.