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#1
12-16-2003, 11:48 AM
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Compression Ratio?
Would someone mind explaining that term to me please? thanks
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 2003 Hyundai Tiburon: Injen CAI, Mussa Single Exhaust, Sparco Four Point Harnesses, RRM Front and Rear Strut Bars, 22mm Rear sway bar, Shark Racing Pedals, Painted Rims. Saving for: Either Big Brake Kit, lines etc, Tien Coilovers Sparco Speed Seat for driver side. 
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#2
12-16-2003, 02:00 PM
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Re: Compression Ratio?
hmmm... don't know a great deal about this subject but my understanding is that compression ratio is generally read in pounds of pressure per cubic inch... here's an example... if you see compression ratio of 10.3 that means there is 10.3 lbs of pressure for every cubic inch of space in your combustion chamber.
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#3
12-16-2003, 07:19 PM
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Re: Compression Ratio?
hmm, so what does that mean preformance wise? does anyone know?
__________________
2003 Hyundai Tiburon: Injen CAI, Mussa Single Exhaust, Sparco Four Point Harnesses, RRM Front and Rear Strut Bars, 22mm Rear sway bar, Shark Racing Pedals, Painted Rims. Saving for: Either Big Brake Kit, lines etc, Tien Coilovers Sparco Speed Seat for driver side.
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#4
12-16-2003, 08:45 PM
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allright here goes,
compression is how tightly packed the air is in the engine. say your engines compression ratio is 10:1(10 to 1). this means that the pistons compressed the air/fuel mixture 10 times its original pressure. the higher the preesure, the more excited the molecules get, resulting in a more violent explosion. this is why low compression pistons are used in turbo engines. the air pressure going in is already pretty high, so if the pistons compress it anymore, it could explode prematurely, causing a condition known as "knock". this is bad, because it will cause the piston to move the opposite way when it is not supposed to causing your engine to go BOOM. so not only do you use lower compression pistons, you use a higher octane fuel. a fuels octane rating is its resistance to burn, so a higher octane fuel also helps in preventing knock.
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#5
12-16-2003, 09:31 PM
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Re: Compression Ratio?
wow you learn something everyday. So what about ratios that are 10:3 (using the Tibs for an example) what does that mean? (10 times 3 times the pressure? "I know I am wrong" lol)
__________________
2003 Hyundai Tiburon: Injen CAI, Mussa Single Exhaust, Sparco Four Point Harnesses, RRM Front and Rear Strut Bars, 22mm Rear sway bar, Shark Racing Pedals, Painted Rims. Saving for: Either Big Brake Kit, lines etc, Tien Coilovers Sparco Speed Seat for driver side.
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#6
12-16-2003, 10:18 PM
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first off, it is not 10:3, it is 10.3 which means 10.3:1. if it were 10:3, this means that since pressure of normal air is 14.7psi in the atmosphere, you find the compresion coeficcient 10/3= 3.33333. this is the same as 3.3333:1. so the pressure at TDC(top dead center or the highest point of the piston) is around 14.7x3.3333= 49 about.
most of the time, compression ratios are just one number, because it is commonly known as being "X:1", so the ":1" is not necessary. i have never even seen a compression ratio of X  a number other than 1), but im sure it exists to indicate very precise measurements.
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