It is not really a big deal that the duration and lift is off by a small amount from the original design. A larger or smaller profile can be chosen easy enough. It is just not acceptable today like it was years ago. Even though the duration and lift numbers were slightly off, the velocity, acceleration, jerk, pressure angle, and radius of curvature values were still close to the original design. Today, the duration and lift numbers may match what is published, but other numbers that are more important are not even considered. Most customers do not look at this part of the cam profile. Since the customer does not care, the camshaft grinder does not care either. That is why cam profiles are still copied and used in the wrong applications.
As long as the camshaft numbers match the specification card, everything is good… right? No, everything is not good. When cam profiles are chosen based on duration and lift alone, much of the cam profile potential is ignored. I have talked about this in previous post, so I will try not to over repeat myself. When base circle diameters and roller wheel diameters are changed from the original design, other important parameters also change, not just the duration. Opening and closing ramps may not be correct for the application. Problems in the valve train can be created including premature wear of the tappets and the valve springs. This can come from excessive values of acceleration, velocity, jerk, pressure angles, and small radius of curvature in the profile flanks or the nose. Unless these parameters are also analyzed, you are just hoping for the best and so is your camshaft grinder. There is much more to a cam profile than just duration and lift.
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