THE FOUR-STROKE CYCLE
WHAT'S THAT?
MECHANICAL PARTS
This type of engine was invented during the 19th century by Nicoulas August Otto
It consists in the most common device in the world able to create motion in our vehichles
HOW DOES IT WORKS?
INTAKE
CRANKSHAFT
PISTONS
TIMING BELT
CONNECTING RODS
SPARK PLUG
VALVES
The piston's role is to absorb the energy emitted by the combustion and transorm it in kinetic energy which produces motion
Cranckshaft role is to transmit the motion created by the combustion of air-fuel mixture to the gear and, finally to the wheels
Spark plug's role is to generate a spark which is foundamental to make the air-fuel mixture explodes in case of benzine engine
The intake and exhaust valves manage the intake and the exhaust stroke by opening or closing themselves
The timing belt connects the camshafts to the crankshaft in order to permit that at a certain rotation of the crankshaft, the camshafts rotate of a certain angle
Connecting rod connects the rod journal to the piston and this part is able to tranform linear movement into circular movement
CAMSHAFT
The camshaft manages the opening and the closing of the intake and exhaust valves
During the intake stroke the intake valves get opened by the camshaft and, inside the cylinder enters the air-fuel mixture. In thos phase the piston i getting down to suck this mixture
COMPRESSION
The piston finally gets up and, by doing this compresses the air fuel mixture which consequently gets increased the pression and the heat
COMBUSTION
The higher temperature reached , anyway, it's not enough to make the air fuel mixture explode. To reach this, It is foundamental the presence of a spark. In this stroke is generated all the energy which the other strokes need. The piston is pushed to the bottom dead center
EXHAUST
In this stroke the camshaft opens the exhaust valves letting the exhaust gas be exhausted in the atmosphere. In this stroke the piston pushes the exhaust gas outside the cylinder reaching the top dead center
CYLINDER
It's the place where all the strokes happen. The main points of the cylinder are the top dead center and the bottom dead center. The distance between TDC and BDC is called engine displacement. The ratio between the volume of the air when the piston at TDC and the one at BDC is called compression ratio. An high value of compression ratio means that the air-fuel mixture will be greatly compressed when the piston gets the TDC