Lobe Profile Graphs

Very nice cam profile graphs can be created from the lift table data if you know how to use Microsoft Excel. It's a little more involved than copy and paste but it's not too difficult. The same information is in the lift table data showing exact numbers but graphs are a good way to analyze a cam profile if you know how to read them. A lot of information can be quickly seen in the graphs. All of the graphs are important to look at but if you only had one graph, the acceleration curve is probably the one to have. In this sample a solid tappet cam profile is symmetrical and the accelerated ramps are designed with the lash settings in the "dip" area. This creates a gentle opening and closing of the valves. This ramp design is usually not necessary on the opening side but if the valve closing speed is not controlled the valve may bounce off the seat or possibly damage parts. The "bowl shape" on the negative side of the curve creates a gentle transition over the nose of the lobe allowing the tappet to easily follow the shape of the lobe. The conservative maximum acceleration will be easy on the valve train and springs. Overall this will be a cam profile that should not cause any unnecessary stress on the valve train. A lot of good information from just a quick look at the acceleration curve.

The lift, velocity, and jerk graphs are the other common curves. The lift and velocity curves should both be a nice smooth curve from zero to the maximum value. Any deviation from the nice smooth curve would indicate a problem with the design itself. The velocity curve will also reflect the type of ramp designs used. The jerk curve will show the changes in the acceleration. Big changes in the jerk curve are normal around the ramp to profile transition. The rest of the curve should be nice and smooth. Any deviation in this area would indicate a design problem.

The lift curve needs to have a resolution of four (.0001) decimal places. Three places at a minimum. The velocity curve needs five decimal places (.00001). The acceleration and jerk curves need eight decimal places (.00000001). That is one hundred-millionth! Your equipment will need to produce the lift table data in the necessary resolutions to create these graphs. Lower resolutions will produce jagged graphs that are useless. Unfortunately what most people use today does not produce quality graphs.