Compression Ratio

scxc15 · September 24th, 2007, 09:25 PM

Is a lower or higher compression ratio better? And what can you do to change your ratio? Also one of my friends has a 2002 GT and said he was going to turbo it but said the ratio wasn't good for it and that a s/c would work with it better. But i herad the new GT's do work well with turbos... hell Idk

HMUSN · September 24th, 2007, 09:26 PM

lower is better for boost
higher is better for NA or nitrous.

scxc15 · September 24th, 2007, 09:29 PM

putting a stroker kit on a car would change the ratio right?

cgstarry · September 24th, 2007, 10:53 PM

I may be wrong on this. But I am learning a ton by tuning up my new '66 mustang with my Son.

The compression ratio is a function of the bottom to top stroke length of the crankshaft / connecting rod / piston head top surface to the remaining headspace in the cylinder head with valves closed.

The only way to change the compression is to play with the headspace by adding / subtracting metal from the piston face, length from the connecting rod, stroke in the crankshaft or remaining space in the head.

My understanding is that the greater the compression ratio the greater the potential energy in the compressed cylinder. This energy can be optimized within limits by adjusting the engine timing.

This is probably basic info but should be fundamentally sound.

Hope it helps!

John

cams-shelbycobra07 · September 24th, 2007, 11:01 PM

Yes john you are correct you can change heads piston or some times gasket to change your compresion and for boost 9:1

September 24th, 2007, 09:25 PM	#1
scxc15 Enthusiast 2003 Mustang V6 15.96@87.08 Join Date: Dec 2006 Location: East Tennessee Posts: 685	Compression Ratio Is a lower or higher compression ratio better? And what can you do to change your ratio? Also one of my friends has a 2002 GT and said he was going to turbo it but said the ratio wasn't good for it and that a s/c would work with it better. But i herad the new GT's do work well with turbos... hell Idk

September 24th, 2007, 09:29 PM	#3
scxc15 Enthusiast 2003 Mustang V6 15.96@87.08 Join Date: Dec 2006 Location: East Tennessee Posts: 685	putting a stroker kit on a car would change the ratio right? __________________ 2003 V6 Mustang 1978 King Cobra

September 24th, 2007, 10:53 PM	#4
cgstarry Regular 2007 Mustang GT, 66 Coupe Join Date: May 2007 Location: Minneapolis, MN Posts: 107	I may be wrong on this. But I am learning a ton by tuning up my new '66 mustang with my Son. The compression ratio is a function of the bottom to top stroke length of the crankshaft / connecting rod / piston head top surface to the remaining headspace in the cylinder head with valves closed. The only way to change the compression is to play with the headspace by adding / subtracting metal from the piston face, length from the connecting rod, stroke in the crankshaft or remaining space in the head. My understanding is that the greater the compression ratio the greater the potential energy in the compressed cylinder. This energy can be optimized within limits by adjusting the engine timing. This is probably basic info but should be fundamentally sound. Hope it helps! John __________________ Vista Blue 2007 Mustang GT Premium Coupe 5 Speed FRPP GTA Axelbacks, AMSOIL XL 5W-20 Steeda CAI w/ High Flow Elbow, SCT xCalibrator 2

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September 24th, 2007, 11:01 PM	#5
cams-shelbycobra07 Enthusiast 1991 LX, 2003 SNK, 2007 S 11.3 Join Date: Dec 2006 Location: Oklahoma City Posts: 956	Yes john you are correct you can change heads piston or some times gasket to change your compresion and for boost 9:1

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