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boit
I've been reading about these two types of engine for quite some time now. With engines of similar displacement, I'm told 2 stroke packs more power. A 4 stroke engine is not necessarily 1/2 as powerful as a 2 stroke since, among other things it has good fuel economy. It is therefore about 2/3 as powerful as a 2 stroke engine. A motorcycle with a 2 stroke engine has a higher acceleration but a 4 stroke engine will win after a couple of miles. That is at constant speed there is on much difference in speed.
That's what puzzles me. If 2 stroke engine has twice as many power stroke as a four stroke, why is that so? It is converting almost twice as much fuel into energy, then why are they having the same output? Why would anyone buy a 2 stroke engine motorcycle anyway if that is true?
Lasand
"I'm told 2 stroke packs more power"

Power-to-weight ratio.

http://en.wikipedia.org/wiki/Power-to-weight_ratio
Lasand
I should have added this also.

http://en.wikipedia.org/wiki/Two-stroke_engine
Whitewolf4869
QUOTE (boit+Apr 3 2012, 10:34 AM)
I've been reading about these two types of engine for quite some time now. With engines of similar displacement, I'm told 2 stroke packs more power. A 4 stroke engine is not necessarily 1/2 as powerful as a 2 stroke since, among other things it has good fuel economy. It is therefore about 2/3 as powerful as a 2 stroke engine. A motorcycle with a 2 stroke engine has a higher acceleration but a 4 stroke engine will win after a couple of miles. That is at constant speed there is on much difference in speed.
That's what puzzles me. If 2 stroke engine has twice as many power stroke as a four stroke, why is that so? It is converting almost twice as much fuel into energy, then why are they having the same output? Why would anyone buy a 2 stroke engine motorcycle anyway if that is true?

The reason a two stroke uses more fuel is because it doesnt burn its fuel completely.
It works by a combination of pressure and vacuum and only has one moving part witch is the crank shaft. That allows for high RPMs 10000 or more.
A four stroke on the other hand has four strokes, intake,compression,ignition,& exhaust. This engine burns clean because the exhaust is forced out before fuel air mixture is sucked in. Unlike the two stroke that is always burning new fuel and old exhaust at the same time. There's ignition the piston goes down and then on the way back up airfuel is sucked into the crank case at the same time exhaust is forced out through a port in the cylinder wall and fresh air fuel comes in under pressure from a port opposite the exhaust port. The piston reaches the top of its stroke and the the spark plug fires and ignition sending the piston on its way back down for another cycle

The four stroke has more moving parts so its more difficult to reach high rpm without engine failure. 6000 rpm would be the upper limit.


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