Cthulu

I'm calculating the stock compression ratio on a 2002 LS1 with the below stock specifications and getting a static CR of 10.36:1 instead of the expected 10.1:1

Is my math wrong? I apologize is this is a noob post, trying to understand where I'm going wrong. I have the negative values in there for Deck clearance volume. I noticed when I take those out it goes back to 10.17:1

5.7 LS1
Bore 3.898
Stroke 3.622
Number of Cylinders 8
Displacement 345.7896451
Chamber Volume 4.068453019
Swept/Cylinder Volume 43.22370564
Gasket Thickness 0.054
Gasket Volume 0.644417478
Rod Length 6.098
Compression Height 1.339
Deck Clearance -0.008
Deck Clearance Volume -0.095469256
Deck Height 9.24
Piston Volume 0
Compression Ratio 10.36104605 (cylinder volume + clearance volume + piston volume + gasket volume + chamber volume divided by clearance volume + piston volume + gasket volume + chamber volume)

Cthulu

So, I redid all my math including the below added variables...still getting 10.36:1 for a stock LS1. Can someone point out what I'm missing?

5.7 LS1
Bore 3.898
Stroke 3.622
Corrected Stroke (minus deck) 3.63
Number of Cylinders 8
Displacement 345.7896451
Chamber Volume 4.068453019
Swept/Cylinder Volume 43.22370564
Gasket Bore 3.905
Gasket Thickness 0.054
Gasket Volume 0.646734036
Piston to Head Volume 0.550921587
Rod Length 6.098
Compression Height 1.339
Deck Clearance -0.008
Deck Clearance Volume -0.095469256
Deck Height 9.24
Piston Volume 0
Ring Height 0.3
Piston to Bore Clearance 0.0021
Crevice/Clearance Volume 0.003856428
Piston to Headgasket Volume 0.003863356
BDC Volume 47.94274912
TDC Volume 4.623237961
Compression Ratio 10.36995057

Cthulu

I still don't understand why I'm getting 10.36 as my compression ratio instead of 10.1:1, Does anyone see where I'm going wrong? A second look by someone would be appreciated.


Static Values below
Bore 3.898
Stroke 3.622
Number of Cylinders 8
Displacement 345.7896451
Gasket Bore 3.905
Gasket Thickness 0.052
Rod Length 6.098
Compression Height 1.337
Deck Clearance -0.006
Deck Clearance Volume -0.071601942
Deck Height 9.24
Ring Height 0.3
Piston to Bore Clearance 0.0014
Piston Volume 0



Calculated Values
Chamber Volume 4.068453019
Swept/Cylinder Volume 43.22370564
Gasket Volume 0.622780924
Piston to Head Volume 0.550921587
Crevice/Clearance Volume 0.002571183
Piston to Headgasket Volume 0.002575801


Below added for BDC Volume
Chamber Volume 4.068453019
Swept/Cylinder Volume 43.22370564
Gasket Volume 0.622780924
Piston Volume 0
Crevice/Clearance Volume 0.002571183
BDC Volume 47.91751076

Below added for TDC Volume
Chamber Volume 4.068453019
Piston to Head Volume 0.550921587
Piston Volume 0
Piston to Headgasket Volume 0.002575801
TDC Volume 4.621950407


Compression Ratio 10.36737882

ez2cdave

Try using this Compression Calculator . . .

Be sure to enter all of your values as POSITIVE numbers ( i.e.- "3cc" for -3cc Flat-Top pistons ), same for Deck Height.

http://www.diamondracing.net/tools/

Cthulu

Well, that's not quite the point. That calculator comes up with 10.17

Which is great, but I don't have the formulas on how it did it. So how do I really trust it?

ez2cdave

Hmm . . . How did you compute your CR before ? Can you trust that method ?

If I can, I'm going to send you an attachment in a PM, if I can . . . If not, we'll use e-mail .