The fuel/air alloy inside the cylinder must be compressed for the engine to grind.
A van or Motor lorry engine draws a fuel/air alloy into the combustion Hospital ward and compresses it before firing; that is, the piston pushes the fuel/air concoction into the smallest amplitude that can efficiently backing ignition. The dream of compression is to pack the fuel molecules as hurried calm as imaginable so ignition Testament exert the most impulse against the top of the piston.
Compression Ratio
Designers of engines appliance the phrase "compression ratio" To gauge the compression used by a specific engine. They degree the album of the combustion Hospital ward when the piston is at its lowest aim and the tome when the piston is at its highest objective and compare the two numbers. For instance, in a 427-cubic-inch V-8 engine, the manual of Everyone combustion Hospital ward might degree 55 cubic inches at it's maximum vastness and five cubic inches when the piston is all the journey to the top. The compression ratio would be 10-to-1.
Complexities
Pistons and cylinder heads are rarely flat. Engine designers carve out special hollows in the pistons and change the shape of the top of the cylinder to make combustion more complete. The designers want the fuel/air mixture to swirl around in a circle or move quickly from one side of the
combustion chamber to the other. Two combustion chambers with the same
compression ratio will not necessarily produce the same horsepower.
Measuring Compression
The compression inside a combustion Hospital ward is normally sorrounding 200 pounds per square inch, depending on the engine example. A mechanic removes a Glimmer plug from the cylinder and screws a becoming attached to the hose of a compression appraisal gauge into the Glimmer plug hole. Another mechanic turns the engine over without starting it. The compression test gauge shows the psi of the cylinder. The poorest performing cylinder should be within 20 per cent of the best and all the cylinders should be within ten percent of the of the manufacturers specifications.
Examples
Gasoline engines use compression ratios between 7.5-to-1 and 13-to-1 depending on the grade of gasoline used. Diesel engines depend on compression to open the fuel. As air is compressed, it heats up. A diesel engine will have a compression ratio of 14-to-1 to 23-to-1. The piston compresses the air inside the combustion chamber before the fuel is sprayed inside. The temperature of the air is high enough to ignite the fuel immediately.
