GASOLINE Engines
GASOLINE (also know as petrol, Benzene and Gasolina) evaporates very quickly giving off highly inflammable vapours. With any gasoline spillage be extremely careful of any naked flames or sparks (i.e. from the vehicles electrical system, welding equipment, cigarettes etc).
THE INDUCTION STROKE (first cycle)
The figure to the left is a simplified cut-away drawing of the internals of a single cylinder engine.
The drawing represents the Piston moving down the cylinder.
The piston is attached to the Crankshaft by means of a connecting rod. As the crankshaft rotates the connecting rod draws the piston downwards.
(The crankshaft rotates clockwise in these diagrams)
Gasoline is converted into a fine mist with the outside air inside a carburettor or an injection system (Both types are not shown in the drawing).
The inlet valve is opened and thus allows the entering of the gasoline and air mixture, into the cylinder, in readiness for the next cycle. During this cycle the exhaust valve remains closed.
THE COMPRESSION STROKE (second cycle)
Both the exhaust valve and the inlet valve are now closed.
The crankshaft continues to rotate, with the aid of a flywheel, and this action forces the piston back up the cylinder bore. As a result of both valves being closed the gasoline / air mixture has nowhere to go, so compression now takes place. The ratio of compression is typically in the range of between (7 to 1) to (11 to 1) depending on the engines designed performance.
The "compression ratio" is that of the ratio of the total volume of the cylinder above the piston when it is in it's lowest position to that of the "combustion" or clearance space when it is at its highest position. (In other words, if 10 cm of air in a bicycle pump were compressed into 1 cm then you would have a "compression ratio" of "10 to 1").
This has now completed one revolution of the crankshaft.