Dynamic compression ratio
From Crankshaft Coalition Wiki
(→Dynamic CR: Updated link for uempistons.) |
|||
| Line 11: | Line 11: | ||
{{Note1}}If the intake valve closing (IVC) point isn't known, it can be calculated: | {{Note1}}If the intake valve closing (IVC) point isn't known, it can be calculated: | ||
| − | # Divide the intake duration by 2 | + | # Divide the advertised intake duration by 2 |
# Add the results to the lobe separation angle (LSA) | # Add the results to the lobe separation angle (LSA) | ||
# Subtract any ground-in advance | # Subtract any ground-in advance | ||
| Line 42: | Line 42: | ||
{{Note1}} Disclaimer<br> | {{Note1}} Disclaimer<br> | ||
| − | + | Like any other, the Keith Black DCR calculator dynamic compression ratio number is a math caclulation just like SCR - cylinder pressures for identical cam/block configurations may vary based on the total system build from intake to exhaust and hinge largely on volumetric efficiency, valve seat and ring condtion. Cylinder pressures at cranking rpm or at max efficiency rpm differ [tracking volumetric efficiency], therefore two different engines with an identical calculated DCR can have one knock, while the other has no issues for the same octane in the powerband as upper limits of fuel are reached. According to the DynoSim software, maximum cylinder pressure is made at or near the torque peak. So, the fact that a motor is not detonating at low rpm 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. | ||
Your Privacy Choices