vassego
Här kommer en förklaring med bland annat vad 5 cylindrar har för fördelar mot 4 och 6 cylindrar. Och att 3 cylindrar har 17% "dövarv".
Källa: "http://en.wikipedia.org/wiki/Straight-5"
The 5-cylinder engine's advantage over a comparable 4-cylinder engine is best understood by considering power strokes and their frequency. A 4-cycle engine fires all its cylinders every 720 degrees — the crankshaft makes two complete rotations. If we assume an even firing engine, we can divide 720 degrees by the number of cylinders to determine how often a power stroke occurs. 720 degrees ÷ 4 = 180 degrees, so a 4-cylinder engine gets a power stroke every 180 degrees. A V8 engine gets a power stroke every 90 degrees, (720° ÷ 8 = 90°).
A given power stroke can last no more than 180 degrees of crankshaft rotation, so the power strokes of a 4-cylinder engine are sequential, with no overlap. At the end of one cylinder's power stroke another cylinder fires.
In a 1-, 2-, or 3-cylinder engine there are times when no power stroke is occurring. In a 3-cylinder engine a power stroke occurs every 240 degrees, (720° ÷ 3 = 240°). Since a power stroke cannot last longer than 180 degrees, this means that a 3-cylinder engine has 60 degrees of "silence" when no power stroke takes place.
A 5-cylinder engine gets a power stroke every 144 degrees (720° ÷ 5 = 144°). Since each power stroke lasts 180 degrees, this means that a power stroke is always in effect. Because of uneven levels of torque during the expansion strokes divided among the 5 cylinders, there is increased secondary-order vibrations. At higher engine speeds, there is an uneven third-order vibration from the crankshaft which occurs every 144 degrees. Because the power strokes have some overlap, a 5-cylinder engine may run more smoothly than a non-overlapping 4-cylinder engine, but only at limited mid-range speeds where second and third-order vibrations are lower.
Every cylinder added beyond five increases the overlap of firing strokes and makes for less primary order vibration. An inline-6 gets a power stroke every 120 degrees. So there is more overlap (180° - 120° = 60°) than in a 5-cylinder engine (180° - 144° = 36°). However, this increase in smoothness of a 6-cylinder engine over a 5-cylinder engine is not as pronounced as that of a 5-cylinder engine over a 4-cylinder engine. The inline-5 loses less power to friction as compared to an inline-6. It also uses fewer parts, and it is physically shorter, so it requires less room in the engine bay, allowing for transverse mounting.
A 5-cylinder engine is longer and more expensive to manufacture than a comparable 4-cylinder engine, but some manufacturers feel these costs are outweighed by its greater capacity in a smaller space than a 6-cylinder.
From the standpoint of driving experience, 5-cylinder engines are noted for combining the best aspects of four and six cylinder engines. They generate more power and torque than four cylinder engines, while maintaining the fuel economy and "pep" of smaller four cylinder engines. Five cylinder turbos have been used on more than one occasion in sport and racing applications for their balance of performance qualities. The Volvo S60 R (racing edition) has a 2.5 liter turbocharged inline 5-cylinder engine which is capable of generating 300 bhp and 295 lb-ft of torque across a large amount of its RPM ranges.
A disadvantage of a straight-5 over a straight-6 is that a straight-5 engine is not inherently balanced. A straight-5 design has free moments (vibrations) of the first and second order, while a straight-6 has zero free moments. This means that no additional balance shafts are needed in a straight-6. By comparison a straight-4 has no free moments of the first or second order, but it does have a large free force of the second order which contributes to the vibration found in unbalanced straight-4 designs.[1]
En kolv på väg upp, en på väg ner, den tredje på väg vart då?
Sedan multiplarna, en R6 eller V6 har väl ändå ett jämnt antal cylindrar?
Samma sak med en R12 eller V12?
