By: Marshall Brain. You find two-stroke engines in such devices as chain saws and jet skis because two-stroke engines have three important advantages over four-stroke engines:. These advantages make two-stroke engines lighter, simpler and less expensive to manufacture.
Two-stroke engines also have the potential to pack about twice the power into the same space because there are twice as many power strokes per revolution. The combination of light weight and twice the power gives two-stroke engines a great power-to-weight ratio compared to many four-stroke engine designs.
You don't normally see two-stroke engines in cars, however. That's because two-stroke engines have a couple of significant disadvantages that will make more sense once we look at how it operates. Do you own a two-stroke bike or any other form of two-stroke vehicle? Post a picture in the comments below to share the two-stroke life with us all! And to check out a two-stroke single cylinder in action, click here! Please confirm you agree to the use of tracking cookies as outlined in the Cookies Policy.
Sign in or register. Michael Fernie 5 years ago. Remind me later. Share Tweet Email Whatsapp. How do they work? Comment below if you had one of these bad boys.
Not quite An array of two-stroke cylinder heads. The cycles 1 MB. What are the pros and cons? Some two-stroke bikes are incredibly cool, like this little Suzuki.
It allows the asymmetric intake of the fuel charge, improving power and economy while widening the power band. Such valves are widely used in motorcycles, ATVs, and marine outboard engines. The intake pathway is opened and closed by a rotating member. A familiar type sometimes seen on small motorcycles is a slotted disk attached to the crankshaft, which covers and uncovers an opening in the end of the crankcase, allowing charge to enter during one portion of the cycle called a disc valve.
Another form of rotary inlet valve used on two-stroke engines employs two cylindrical members with suitable cutouts arranged to rotate one within the other — the inlet pipe having passage to the crankcase only when the two cutouts coincide. The crankshaft itself may form one of the members, as in most glow-plug model engines.
In another version, the crank disc is arranged to be a close-clearance fit in the crankcase and is provided with a cutout that lines up with an inlet passage in the crankcase wall at the appropriate time, as in Vespa motor scooters. In a cross-flow engine, the transfer and exhaust ports are on opposite sides of the cylinder, and a deflector on the top of the piston directs the fresh intake charge into the upper part of the cylinder, pushing the residual exhaust gas down the other side of the deflector and out the exhaust port.
This method of scavenging uses carefully shaped and positioned transfer ports to direct the flow of fresh mixture toward the combustion chamber as it enters the cylinder. Usually, a piston deflector is not required, so this approach has a distinct advantage over the cross-flow scheme. The scavenging gas flow is, therefore, in one direction only, hence the name uniflow. The units run in pairs, with the lower half of one piston charging an adjacent combustion chamber.
What is a Two-Stroke Engine?
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