.:HSTuners::

04-02-2002, 01:50 AM

what exactly is the compression ratio? can i get some info on that? why is it so very importan?

94_AcCoRd_EX · 04-02-2002, 01:54 AM

Compression ratio is the ratio of the total volume of the cylinder and combustion chamber with the piston at BDC (bottom dead center) and TDC (top dead center)...

04-02-2002, 02:05 AM

can you run that by me one more time?

*AzCivic* · 04-02-2002, 12:32 PM

ok when the piston is at the bottom of the stroke(BDC) that is the 1 in the compression ratio ex. 9:(1) and when it reaches the top of the stroke(TDC) that air is compressed 9 times smaller than it original volume hence the 9 in 9:1 . the higher the compression ratio the more power there is to be had but you'll also risk detonation(the air and gas self igniting at a bad time) which will ruin an engine unless you run race gas which has a higher octane(higher octane= more resistance to detonation).
On the street 11:1 is as high as you want to go, but with a turbo you'll want a 8.5:1 or so compression. Hope this helps.

04-02-2002, 12:38 PM

Why do we use lower compression with FI?

*AzCivic* · 04-02-2002, 12:42 PM

a turbo forces more air into the cylinder so in a way it increases compression plus the if your intercooler sucks then the intake charge will be hella hot and again give you another chance for detonation.

04-02-2002, 01:50 AM	#1
yelizardking Posts: n/a	c/r what exactly is the compression ratio? can i get some info on that? why is it so very importan?

04-02-2002, 01:54 AM	#2
94_AcCoRd_EX Insomniac Moderator Join Date: Aug 2001 Location: OR Age: 44 Posts: 11,142	Compression ratio is the ratio of the total volume of the cylinder and combustion chamber with the piston at BDC (bottom dead center) and TDC (top dead center)... __________________ 1994 Accord EX coupe --Need hosting for your pics on HST? PM me...--

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04-02-2002, 02:05 AM	#3
yelizardking Posts: n/a	can you run that by me one more time?

04-02-2002, 12:32 PM	#4
AzCivic Moderator Join Date: Feb 2002 Location: Az Age: 44 Posts: 3,804	ok when the piston is at the bottom of the stroke(BDC) that is the 1 in the compression ratio ex. 9:(1) and when it reaches the top of the stroke(TDC) that air is compressed 9 times smaller than it original volume hence the 9 in 9:1 . the higher the compression ratio the more power there is to be had but you'll also risk detonation(the air and gas self igniting at a bad time) which will ruin an engine unless you run race gas which has a higher octane(higher octane= more resistance to detonation). On the street 11:1 is as high as you want to go, but with a turbo you'll want a 8.5:1 or so compression. Hope this helps.

04-02-2002, 12:38 PM	#5
Mushroom Posts: n/a	Why do we use lower compression with FI?

04-02-2002, 12:42 PM	#6
AzCivic Moderator Join Date: Feb 2002 Location: Az Age: 44 Posts: 3,804	a turbo forces more air into the cylinder so in a way it increases compression plus the if your intercooler sucks then the intake charge will be hella hot and again give you another chance for detonation.