You can see the differences in thrust vs non thrust surface area here. JE aslo applied their polymer skirt coating. The coating helps reduce friction and improve wear of both the piston skirt and the cylinder walls. The JE pistons are coated just like the OEM parts!
Our pistons have the top compression ring moved down for more strength. The top ring groove also has gas ports that allow combustion gas to more easily get behind the ring to improve sealing. There is a pressure equalization groove between the #1 and #2 compression rings which acts like a pressure reservoir to help the #2 ring seal better. You can also see our offset piston pin bore which will reduce piston slap and noise, working with the offset crank centerline.
When compared to the stock piston, you can see that our JE piston has less of a dome, and has a deeper pre-chamber and valve reliefs. All of this reduces the compression ratio from 12.5:1 to a more boost-friendly 10:1. We were careful to maintain the turbulence-inducing quench pads.
In this side view you can see how we lowered the #1 compression ring to give the ring land more strength and pinch resistance. You can see that the JE piston has a more narrow skirt to reduce friction even though it is the wide side of the asymmetrical design.
Our rings are provided by JE, the #1 compression ring is a 1mm low tension nitrided steel part while the #2 ring is a 1.2mm ductile iron ring with a naiper profile. The top ring is hard and wear resistant while the second ring conforms to the cylinder quickly and starts to provide seal with very little break-in. The oil ring is a narrow low tension nitrided steel part. These rings are wear resistant and break in quickly even though those factors are usually diametrically opposed.
