Explain tha actions of two strokes cycle.?

Question

Technology Automotive

Answer 1

on a 4 stroke you have

(piston going down sucks in gas)

Piston goes up compress gas

Spark ingnites...Bang! pressure pushes piston down power stroke.

Piston comes back up blows burnt gas out to exhaust.

On a 2 stroke;

piston is pushed upwards. This does two things. One, the rising piston generates a vacuum in the sealed crankcase which pulls a fresh air/fuel charge from the carburetor into the crankcase (thus the reason for having to add lubricating oil to the gas for 2 cycle engines). A small reed valve (a one way valve) allows the mixture to enter the crankcase, but not leave by the same path. At the same time, the rising piston is also compressing the previous charge in the combustion chamber. As the piston nears the top of the stroke, the ignition system ignites the charge in the combustion chamber.

downward motion of the piston turns the crankshaft, providing power output. In addition, the downward motion is pressurizing the air/fuel mixture previously loaded in the crankcase. As the piston continues it's travel down the cylinder bore, it will first expose the exhaust port in one side of the cylinder. The spent gases from the burning mixture are then released to the exhaust system. A small amount of further piston travel down the cylinder now exposes the intake port. At this point, the now pressurized mixture in the crankcase is released into the combustion chamber through the intake port. A piston dome design, unique to 2 cycle engines, is used to help 'sweep' the chamber clean of spent exhaust gases by directing the incoming rush of air/fuel up towards the cylinder head and then down towards the exhaust port. As the crankshaft continues it's rotation, the piston will eventually reach the bottom of it's stroke  

Answer 2

This is one of the better animations I've found.

Answer 3

2 stroke - the piston moves up once (1 stroke) and down once (1 stroke) - it takes 2 strokes, to make a complete cycle - 2 functions are happening on each stroke - intake & compression on the piston's up stroke and power & exhaust on the piston's down stroke.



The cylinder has holes in the cylinder wall - they're called ports.

Intake port & exhaust port.

Also transfer ports - I'll explain them later.



The exhaust pipe is bolted to the front of the cylinder, at the exhaust port.

The carburetor is bolted to the rear of the cylinder, at the intake port.

Same as a 4 stroke.



Between the carburetor and cylinder is the reed valve.

The reed valve can be a flap of flexible sheet metal, or more popular in motorcycles - thin sheets of plastic.

The reeds are in the closed position to prevent fuel from escaping the cylinder - the vacuum of the engine, causes them to flex open, allowing fuel to enter.



Piston on it's up stroke - creates a negative pressure in the bottom end (bottom end is everything under the piston, connecting rod, big end bearing and the entire area surrounding the crankshaft).

Negative pressure, as in sucking liquid into a hypodermic needle.

The reed valve is sucked open and fuel from the carb is sucked through the intake port and is temopraily stored in the bottom end.



Piston on it's down stroke - the rings move below the intake port.

No more suction is created, allowing the reed valve to flex closed.



While the piston is moving down, it's compressing the fuel in the bottom end.

Instead of compressing the fuel, the fuel is pushed up through the transfer ports.

The transfer ports are like the water jackets of a water cooled engine.

The fuel is pushed up through the transfers and into the cylinder through the transfer ports.



Piston on it's up stroke - the rings move above the intake port, creating a vacuum in the bottom end (intake stroke).

Also with the rings above the intake port, fuel from the cylinder cannot escape.

With the piston rising, the fuel is being compressed (compression stroke).



The spark plug fires, ignites the fuel, pushing the piston down (power stroke).

With the piston moving down, the rings pass the exhaust port (opening the hole), and burnt fuel escapes.

http://science.howstuffworks.com/two-str...