Clear evidence of JE’s attention to detail is seen in its unique line of asymmetrical pistons that incorporate different skirt panel widths for the major thrust side of the piston versus the minor thrust side.
The less drag created by the skirt on the bore equals more power.
Ring stability at the piston rockover point and subsequent pressure build is very critical and largely controlled by the piston skirt.
Frictional forces on the skirt and the skirt lubrication characteristics are also critical for trouble-free operation.
This means that the area of largest expansion requires the entire length of the skirt to be ovalized to meet its maximum expansion requirement.
It allows the piston to expand and run without seizure in the cylinder, but results in a less than desirable loose fit of the remaining skirt area, which can contribute to inaccurate guidance of the piston in the bore and reduced ring stability.
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Engine performance is significantly impacted by the friction force against the cylinder wall and piston rock over which can affect piston ring seal.