Dynamic compression ratio
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Just for grins, I calculated different static compression ratios with a 3.48" stroke and different camshaft intake closing points @ 0.050" tappet lift on Keith Black's dynamic compression ratio calculator. The calculator went ka-flooey on 8.00, so we'll start at 8.25 SCR. I kept the DCR at just over 8.0, a figure that is well accepted for operation of the motor on pump gas with a little cushion... | Just for grins, I calculated different static compression ratios with a 3.48" stroke and different camshaft intake closing points @ 0.050" tappet lift on Keith Black's dynamic compression ratio calculator. The calculator went ka-flooey on 8.00, so we'll start at 8.25 SCR. I kept the DCR at just over 8.0, a figure that is well accepted for operation of the motor on pump gas with a little cushion... | ||
| − | Static CR....Intake closing point @ 0.050"....Dynamic CR | + | *Static CR....Intake closing point @ 0.050"....Dynamic CR. |
| − | 8.25........10* ABDC......8.010 | + | *8.25........10* ABDC......8.010........................................................................................................ |
| − | 8.50........20............8.012 | + | *8.50........20............8.012........................................................................................................ |
| − | 8.75........27............8.022 | + | *8.75........27............8.022........................................................................................................ |
| − | 9.00........33............8.018 | + | *9.00........33............8.018........................................................................................................ |
| − | 9.25........37............8.061 | + | *9.25........37............8.061........................................................................................................ |
| − | 9.50........42............8.029 | + | *9.50........42............8.029........................................................................................................ |
| − | 9.75........46............8.016 | + | *9.75........46............8.016........................................................................................................ |
| − | 10.00.......49............8.038 | + | *10.00.......49............8.038........................................................................................................ |
| − | 10.25.......52............8.043 | + | *10.25.......52............8.043........................................................................................................ |
| − | 10.50.......55............8.029 | + | *10.50.......55............8.029........................................................................................................ |
| − | 10.75.......57............8.069 | + | *10.75.......57............8.069........................................................................................................ |
| − | 11.00.......60............8.022 | + | *11.00.......60............8.022........................................................................................................ |
| − | 11.25.......62............8.038 | + | *11.25.......62............8.038........................................................................................................ |
| − | 11.50.......64............8.042 | + | *11.50.......64............8.042........................................................................................................ |
| − | 11.75.......66............8.035 | + | *11.75.......66............8.035........................................................................................................ |
| − | 12.00.......68............8.017 | + | *12.00.......68............8.017........................................................................................................ |
| − | Now, it's unclear where these dynamic cr readings are taken, at cranking rpm's or at max efficiency rpm's. But I can tell you this from playing with the DynoSim, max cylinder pressures are made at or near the torque peak. So, the fact that a motor is not detonating at low rpm's does not mean that it will not detonate at or close to the torque peak. | + | Now, it's unclear where these Keith Black DCR calculator dynamic cr readings are taken, at cranking rpm's or at max efficiency rpm's. But I can tell you this from playing with the DynoSim, max cylinder pressures are made at or near the torque peak. So, the fact that a motor is not detonating at low rpm's does not mean that it will not detonate at or close to the torque peak. |
These numbers may not mean anything at all, but they do illustrate that you cannot just pick a cam out of thin air like a lot of fellows do and expect it to work best for your particular combination. | These numbers may not mean anything at all, but they do illustrate that you cannot just pick a cam out of thin air like a lot of fellows do and expect it to work best for your particular combination. | ||
[[Category:Engine]] | [[Category:Engine]] | ||
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