JE Pistons Defines Piston Ring Shape Terminology

Widely known for piston lines ranging from street/strip applications to the ultimate in high-end performance, JE Pistons also offers a complete piston ring program titled Pro Seal Rings. On top of their eight different ring design offerings ranging from Sportsman Series to Professional Race Series lines, JE also offers custom ring options.

JE’s custom ring solutions can tailor ring designs to your specific high-performance needs. Their custom ring department is armed with the latest ring design, manufacture, and analysis equipment. The JE catalog offers an extensive technical section pertaining to ring terminology along with piston ring shapes and functions.

Piston Ring D-Wall 
The D-wall is a standardized description of both compression rings’ face shape of the top compression established by the Society of Automotive Engineers (SAE) that dictates the radial width of a standard automotive piston ring by using the following formula; Bore diameter ÷ 22 = radial thickness. (4.000″ ÷ 22=.182″.)

Ring terminology is broken down into five major applications. Each of these ring designs has a specific advantage for varying motorsports applications.

Piston Ring Back Cut

This terminology is used to describe a compression ring with less than SAE standard D-Wall radial thickness. The radial thickness is defined as the ring’s inside diameter compared to the outside diameter. Back-cutting reduces natural radial ring tension by increasing the inside diameter. In applications where there is a tight top ring land-to-piston clearance problem, back cut rings allow them to be moved up toward the top of the piston, which improves combustion efficiency and provides more power.

The next two examples of terminology refer to an engineered ring “twist.” The ring is bevel cut in either an upward or downward direction in relation to the cylinder wall. These rings are slightly smaller than the piston groove, promoting this twist or rocking action.

Piston Ring Positive Twist

A ring with an asymmetric cross-section indicates the ring has an asymmetric design, not identical on both sides of its centerline. This angled face causes it to twist upward towards the piston crown. This engineered twist aids in ring sealing of the top and bottom of the ring groove. The positive twist is used only on top compression rings.

Piston Ring Reverse Twist

In contrast to a ring with a positive twist design, a reverse twist is also an asymmetric change to the ring’s cross-section causing it to twist downward towards the piston skirt. This engineering is used on the second compression ring for more oil scraping properties.

Piston Ring Neutral Design

The term neutral is used to describe a piston ring that rides flat upon the piston ring groove and has no torsional bias or twist.

JE Piston’s performance and application matrix is charted to assist in selecting the ring type appropriate for your application.

The JE catalog offers 10 pages covering rings with suggested options appropriate for your type of performance or racing engine. There is also a part number “decoder” chart to assist in breaking down a Pro Seal Rings top ring, second ring, and oil ring design in each set.

Reviewing the JE Pistons catalog is not just educational for your next engine project; it also defines the latest in piston ring technology. There are also applicable racing engine formulas and specific lessons on how your piston and ring design best function with your particular high-horsepower engine.

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About the author

Todd Silvey

Todd has been a hardcore drag racing journalist since 1987. He is constantly on both sides of the guardwall from racing photography and editorship to drag racing cars of every shape and class.
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