Necessity of compressing the airfuel mixture
When an uncompressed air-fuel mixture is ignited, it burns slowly due to the low density of fuel and air. However, when compressed air-fuel mixture is ignited, the high density causes the mixture to suddenly burn (explode). Even when the fuel mixture is the same, a compressed mixture will release more power than an uncompressed mixture when ignited. Furthermore, compressing the air-fuel mixture causes the fuel and air to mix more thoroughly, resulting in a higher rate of vaporization of the gasoline and higher temperature when ignited. The compressed air-fuel mixture also burns more easily than before. The level of compression of the air-fuel mixture is expressed in the compression ratio. Generally, the greater explosive pressure can be attained when the compression pressure is higher. However the knocking occurs if the pressure is too high. Therefore, the compression ratio of the gasoline engine is normally designed to be between to 11.
Good Spark
The gasoline engine converts the combustion of the air-fuel mixture to motive force. In order for the air-fuel mixture to burn well, it is important to have a powerful enough spark with proper ignition timing.
Conditions for a good spark
(1) Ability to generate a powerful spark enough for the air-fuel mixture to burn (explode) The spark plug in a gasoline engine generates a spark to burn the air-fuel mixture. If the spark is weak, there will not be enough energy to ignite the air-fuel mixture. For that reason, a powerful spark is essential.
(2) Ability to keep the proper ignition timing for every engine condition The ignition timing changes according to engine speed or load to ensure that there is always proper ignition timing.
Components of a standard Automotive Engine
The engine is made of many components to help it convert heat energy into mechanical energy efficiently when the air-fuel mixture is burned.
1. Cylinder head
(1) Cylinder head
(2) Cylinder head gasket
2. Cylinder block
3. Crankshaft
(1) Crankshaft
(2) Bearing cap
4. Connecting rods
(1) Connecting rod
(2) Bearing cap
5. Bearings
(1) Connecting rod bearing
(2) Crankshaft bearing
(3) Thrust washer
6. Pistons
(1) Piston
(2) Piston pin
(3) Piston rings
7. Valve mechanism etc.
(1) Exhaust camshaft
(2) Intake camshaft
(3) Valve lifter
(4) Keeper
(5) Valve spring retainer
(6) Valve spring
(7) Valve stem oil seal
(8) Spring seat
(9) Valve
(10)Timing chain
(11)Chain tensioner slipper
(12)Chain vibration damper
(13) Timing chain tensioner
(14)Crankshaft timing sprocket
When these components function correctly, motive force is produced.