Crankshaft and Bearing Analysis Process for a Light Duty Automotive Engine

Design of a light duty diesel for an automotive market presents contradictory challenges related to passenger car requirements for a compact, low weight design versus the diesel's base engine that must withstand cylinder pressures that are much greater than that seen on gasoline. This was a particular challenge for Cummins because of two reasons. First, design practices developed for Cummins' traditional heavy duty and industrial markets could lead to over-design, particularly for those items that have wear based life limits like bearings. Secondly, in the pursuit of new engine business it is necessary to be able to quickly yet accurately generate conceptual engine space claims for a variety of vehicle and engine specifications. When applying traditional guidelines for crank and bearing sizing, the resulting base engine size appeared an unsolvable problem relative to size and weight requirements. To overcome these difficulties a number of new processes have been established, two of which are described in this paper.