Four Stroke vs Two Stroke Engines
Both gasoline and diesel engines are available in either two-stroke or four-stroke format. Stroke means the movement of the piston that is inside the engine. In two stroke engines, there is only one stroke in to each direction. It has a compression stroke as well as an exhaust stroke. However, unlike in two stroke engines, four stroke engines have compression, exhaust strokes, and return strokes for each of those strokes. The procedure of both two stroke and four stroke engines are the same, since they have an intake, compression, combustion (power stroke), and an exhaust, events. The main difference is that, in two stroke engines, all these 4 events occur in two upward strokes and two downward strokes. But in 4 stroke engines they occur in separate strokes. Basically, both the two stroke and four stroke engines are internal combustion engines.
Two Stroke Engine
As the name suggests, it has only two strokes per cycle; a stroke during intake and compression, and the other during combustion and exhaust. In two stroke engine, it has 2 ports for the inlet and the exhaust purposes. That means it has no valves so that it has a simple structure than a four stroke engine. The function of the valves is done by the piston and those 2 ports. Generally, two stroke engines can be seen in chainsaw because of its simple structure. Because unlike 4 stroke engines, 2 stroke engines are lighter. And also two stroke engines have combustion event in each and every resolution. Due to this reason it has a significant power boost. Therefore, considering these two factors it is apparent that it has a higher power-to-weight ratio. At the same time, two stroke engines can be used in any orientation since it lacks the oil sump. Though it is better to have a good lubricating system to lubricate the crank shaft, cylinder walls and connecting rods, two stroke engines do not have a proper lubricating system. Instead, they use a fuel and a gas mixture. Therefore, that it generates more pollution. And also most of the two stroke engines experience a faster wear and a shorter engine life. However, two-stroke engine has won a good name in the market due to its high performances and lightweight.
Four Stroke Engine
Four-stroke engine has four strokes per cycle and those are intake, compression, combustion and exhaust. In four-stroke engine, it has spark for every two turns of the crankshaft. So that, when comparing two engines of two stroke and four stroke with equal size, four-stroke engine is half as powerful as two-stroke engine. However, four-stroke engine has a fine lubricating system. Therefore, they last longer than two stroke engines. In addition, when using gas, four-stroke engine is more efficient. Therefore, pollution occurs in a small amount. Normally, four-stroke engine has so many parts that make it more complex. At the same time, it has valves for intake and exhaust processes. Since this has valves and dedicated intake, compression, power and exhaust strokes, the fuel consumption is getting better. In four-stroke engine, it produces more torque at low RPM.
What is the difference between Two Stroke and Four Stroke Engines?
• Four stroke engine has more moving parts than two stroke engine.
• Four stroke engine is heavier than 2 stroke engine.
• Four stroke engine is more expensive.
• Two stroke engine produces more pollution than four stroke engine.
• Two stroke engine does not have a lubricating system but four stroke does.
• Two stroke has no valves, but four stroke has it.
• Two stroke has a short engine than four stroke engine.
• Two stroke engine consumes more fuel capacity than a four stroke.
• Four stroke has less pollution than two stroke.
• Four stroke engine has high compression ratio and high thermal efficiency.
• Two stroke engine has a much simpler design.