Re: What does loop scavenged mean?
Say, What. In 2 stroke engines, we use the term scavenge to describe how the fuel/air mixture clears burned gasses from the cylinder and "charges" it afresh.<br /><br />The simplest 2 strokes use cross flow, cross charge or cross scavenging (same thing). The fuel/air mix travels from the crankcase and enters one side of the cylinder. It is then deflected toward the head by a deflector on the top of the piston, crosses the top of the cylinder and comes down the other side toward the exhaust ports, which are opposite the scavenging (intake) ports. Because the charge crosses the cylinder from one side to the other, we call it cross flow, or cross scavenging. It's weaknesses are: the deflector on the piston prevents ideal combustion and complete scavenging, limits compression ratio and makes the piston heavier than a flat-topped piston would be.<br /><br />Loop charged or loop scavenged (same thing) engines are preferred. There are two sets of intake, or scavenging ports. They are set roughly opposite each other and angled toward the side of the cylinder opposite the exhaust ports. The two scavenging charges enter the cylinder and merge at the side of the cylinder opposite the exhaust ports, turn up, and LOOP over themselves back down to the exhaust ports. The result is more complete scavenging with a more concentrated charge. The flat-top piston is lighter, allows ideal combustion geometry (domed combustion chamber, centered spark) and maintains a more even temperature.<br /><br />Does that help? Any more questions?<br /><br />Red sky at night, sailor's delight.<br />Red sky at morning, sailor take warning!<br /><br />JB
