How does a car engine works? (The four stroke engine mechanism)?

Question

Wikipedia states the following:

"The compression stroke is the second of four stages in an otto cycle or diesel cycle internal combustion engine.

In this stage, the mixture of air and petroleum is "compressed" to the top of the cylinder by the piston until it is either ignited by a spark plug in an Otto engine"

What I really want to know is, how does the "compression" occurs? I mean, it can't just "compress", there must be some sort of mechanism or source of energy to instigate the "compression". How does it occur?

Answer 1

When the crank shaft is turned by a starter motor the pistons move up/down in response to the truning crank shaft. As the crank shaft is turned the pistons in the various cylinders complete whatever portion of the combustion cycle they are on. As the cranshaft rotates during starting eventually one piston will perform its compression stroke. Eventually the motor starts running.


When the motor is running the up/down movment of the pistons is converted into a rotary motion by the crank shaft. The crankshaft is connected to a mass of metal called a fly wheel. THe momentum of which is used to assist with keeping the crankshaft turning. The flywheel has gear teeth along the outside circumference , this is called a ring gear and is where the starter motors pinion gear is engaged to turn the motor over for starting.
THe transmission / clutch is attached to the fly wheel.


Single cylinder engines rely on the rotating mass of a flywheel,counter weight and/ or mass of the rotating parts to carry enough momentium to rotate the crank shaft to the next power stroke.

In cars where multiple cylinders are available each cylinder is performing a combustion cycle at a slightly different time than the others. This means that a power stroke is applyied to the crankshaft more frequently so the crankshaft only needs to move a part of a revolution before having power applied to it from a cylinder. Since power is applied to the crank by multiple cylinders some of this power is used by the other cylinders to carry them through the rest of their cycle. Also in multi cylinder engines a smaller flywheel is used since momentium is no longer the only means to carry pistons through the rest of the cycle.

Answer 2

Car Engine Working Mechanism

Answer 3

Both the inlet and exhaust valves are shut and the rising piston compresses the air petrol mixture.This is aided by flywheel momentum.

Answer 4

gas is injected into the cylinder either from the carbuerator of from fuel injection nozzle and is compressed by piston, ignited by spark plug forcing piston down and allowiung exhause to escape.