The piston pin bushing is tough silicon bronze, one of the most wear resistant bushing materials available. As the rod bolts are the most critical part on the connecting rod, no expense was spared here. Eagle uses genuine ARP 2000 3/8″ rod bolts on all of their sport compact series of rods. These rod bolts have a tensile strength of over 230,000 psi, many times stronger than the factory bolts.
We took our Eagle rods to our local machine shop and had the big ends narrowed by 0.022” on both sides. We then had our rods WPC treated to smooth the machined sides of the big end and reduce friction from the pin bushing. The rods probably got a nice gain in fatigue strength as well from the treatment. Read about how WPC Treatment works here!
|Check out JE’s FEA output on our pistons. The warmer the color, the higher the stress in this area. There are hardly any areas of stress concentration on our pistons! Below is the FEA output from different viewing positions.
To accommodate the longer H22 connecting rod, we contacted JE Pistons to design and manufacture a custom piston with a shorter pin height. We turned to JE Pistons for their superior two week lead-times and their extensive use of Finite Element Analysis (FEA) software in their design process. Surprisingly, the use of these tools can be quite rare in the custom piston industry with the exception of some of the bigger players like Cosworth.
In the case of piston design, the FEA process utilizes thermal and mechanical loads to simulate engine running conditions. Load cases are derived and applied to the components based on the engine application and specifications including peak power, torque, and geometry. The analysis results can be used to effectively evaluate part longevity and wear patterns to ensure a robust piston design.
|FEA was applied to the piston pins as well. One of the reasons why we went with a straight wall wrist pin was the increased deformation of a tapered pin shown in the FEA. Our pins were WPC treated as well, a sort of poor man’s DLC.