How are the number of cam lobes determined ?
The number of lobes, the gear ratio and direction of rotation are designed as follows : Where ” X ” is the number of intake or exhaust lobes on the cam. ” Y ” is the number cylinders, and ” R ” is the gear ratio relative to the crankshaft. For cams running in the opposite direction to the crankshaft X = ( Y – 1 ) / 2 and R = Y-1 For cams running in the same direction to the crankshaft X = ( Y + 1 ) / 2 and R = Y+1 Generally opposite rotation is favored as the cam speed is lower, this reduces the relative velocity between the cam lobes and the tappets, also it results in fewer lobes to be machined. There are two rows of cam lobes, one for the inlet valves and one for the exhaust valves. This allows the different inlet cam and exhaust cam durations to be optimized.
