compression ratios?

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Jun 28, 2003

aznstylez254

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compression ratios?

can someone explain this to me... whats the point of having high or low compression?
im sorry if this is something im already supposed to know.

Jun 28, 2003

Boilermaker1

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High compression makes more power in naturally aspirated engines because you can pack a lot of air in, then compress it into a very small area... the pressure it creates gives you the power.... when a car is 11:1 compression, that means there is 11 times the volume at the bottom of the stroke as there is at the top... The spark and ensuing explosion that occurs when the piston nears the top forces it back down, turning the crank over.
Low compression is usually used on cars with forced induction (Turbo or supercharged) because the air is already pressurized coming in. Using high compression and pressurized air creates a tremendous amount of heat that usually causes lots of problems. You will find that both high compression N/A engines and Turbo/SC engines have very effective cooling systems to keep the engine cool... because both can create a lot of heat.
Theres probably a more in depth explaination somewhere online, but I don't feel like looking for it.