compression, what is it?

[tidyneil]

ive read so many posts of people talking about compression, i try to pretend i understand but i honestly have no idea, ive read the sticky above but i think its more of a calculator to see what you compression is,

so if someone could explain is simple terms then i'd much appreciate it.

[Championship White]

A compression ratio?

It's the volume of the combustion chamber and cylinder written as a ratio from the largest capacity (when the piston is at the bottom of its stroke) to the smallest capacity (the piston at the top of the stroke).

So if the total volume of the cylinder and combustion chamber is 1000cc when the piston is at the bottom of its stroke and 100cc when the piston has moved to the top of its stroke the volume then it has a compression ratio of 10:1.

Higher ratios allow more efficient burning of fuel and air but the higher ratio you use the better the fuel which has to be used as lower octane fuels will cause detonation.

[blinx9900]

in simple terms its how much the air/fuel mixture is compressed before it is ignited

[pateras_vtec]

note that there are two types of compression. static and dynamic.

[tama666]

compression = squish

Here is a link with a very good illustration of a 4 stroke motor in motion.

Stroke 2 of 4: With both intake and exhaust valves closed, the piston returns to the top of the cylinder compressing the fuel-air mixture. This is known as the compression stroke.

Four-stroke engine - Wikipedia, the free encyclopedia

[tidyneil]

wow, very complicated, but i do kinda understand it a little now, thanks.

[tama666]

Originally Posted by tidyneil

wow, very complicated, but i do kinda understand it a little now, thanks.

...complicated, yes, somewhat, complicated only for the reason its a crude mix of out dated fossil fuel burning methods [that a whole different rant].

The biggest issue with compression is that it heats up what ever is being compressed, and there is the problem, contributes to detonation and pre-ignition. Very high compression will cause very high temps and that is not good for cheep low octane fuel vapor as it will "light" or explode without the help of a spark plug. One has to keep their local fuel availability in mind when building a higher compression engine, or use race fuel all the time.

...sorry for the long post