Does this compression calculator seems accurate?
Does this compression calculator seems accurate? Is more needed to get the true answer?
This is what I have so far, and its the only one that has not given me a crazy answer like 7:5:1
I'd like to know the formula for finding the real answer rather than plugging it in, or make my own calculator. I have looked at the other threads, and did not come up with much other than dead links, and programs requiring excel which I do not have.
This is what I have so far, and its the only one that has not given me a crazy answer like 7:5:1
I'd like to know the formula for finding the real answer rather than plugging it in, or make my own calculator. I have looked at the other threads, and did not come up with much other than dead links, and programs requiring excel which I do not have.
This calculator is making the assumption that at TDC, the piston is flush with the deck surface of the block. This may or may not be true for the particular setup you're running - you would also need rod length, head gasket bore, and piston compression height to get an accurate number.
static compression ratio = (cylinder volume at BDC) / (cylinder volume at TDC)
BDC volume = (swept volume)+(gasket volume)+(combustion chamber volume)+(piston dish)
TDC volume = (combustion chamber volume)+(gasket volume)+(piston dish)+(piston-to-deck volume)
static compression ratio = (cylinder volume at BDC) / (cylinder volume at TDC)
BDC volume = (swept volume)+(gasket volume)+(combustion chamber volume)+(piston dish)
TDC volume = (combustion chamber volume)+(gasket volume)+(piston dish)+(piston-to-deck volume)
Last edited by ckpitt55; Dec 18, 2012 at 12:49 AM.
Most online calculators are going to be just rough estimates. It can get really fuzzy when you factor in ring land volume and actual gasket bore and thickness. The formula above is the jist of it for static. Dynamic is another animal.
This calculator is making the assumption that at TDC, the piston is flush with the deck surface of the block. This may or may not be true for the particular setup you're running - you would also need rod length, head gasket bore, and piston compression height to get an accurate number.
static compression ratio = (cylinder volume at BDC) / (cylinder volume at TDC)
BDC volume = (swept volume)+(gasket volume)+(combustion chamber volume)+(piston dish)
TDC volume = (combustion chamber volume)+(gasket volume)+(piston dish)+(piston-to-deck volume)
static compression ratio = (cylinder volume at BDC) / (cylinder volume at TDC)
BDC volume = (swept volume)+(gasket volume)+(combustion chamber volume)+(piston dish)
TDC volume = (combustion chamber volume)+(gasket volume)+(piston dish)+(piston-to-deck volume)
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Exactly, they are just tools to get a good estimate of compression. 9.52 vs 9.59:1....who cares?
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COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
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Verdad Gallardo The calculator he used asks you to add or subtract the piston being in or out of the hole in the same line as gasket thickness. If the piston is out .005", you take the .005" from the .051" thick gasket, if it's in the hole, you add it to the thickness of the gasket. They just saved one step/calculation.
No big deal! I was looking for it as well, and didn't find it until I slowed down and read all the descriptions. 
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COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
Yea usually when I calculate compression I assume a couple different scenarios as far as piston being out of the hole or in the hole and usually it is a negligible effect, like other guy said 9.52 or 9.59 same difference..
Of all the variables to be assumed, you pick the most critical...yea, it won't change compression by much, but there is no reason at all that you should have to guess on that. You should know deck clearance exactly.
thanks for the replies. yeah I kept being told my compression is 9:3:1 (and im betting it is)
rods are 6.125
i have ls9 gaskets
lq9 block with (ive been told is a 9.225 deck)
heads are 3/4 deck
any more info i dont really have other than cam profile. 232/240 .595 /608 115
for some reason I thought all of that would come together to get the true result......but I am really more interested in the math behind it. Wanted to get the formula for the real answer.
Example
RL+DH/GT= Compression
rods are 6.125
i have ls9 gaskets
lq9 block with (ive been told is a 9.225 deck)
heads are 3/4 deck
any more info i dont really have other than cam profile. 232/240 .595 /608 115
for some reason I thought all of that would come together to get the true result......but I am really more interested in the math behind it. Wanted to get the formula for the real answer.
Example
RL+DH/GT= Compression
