CYL I NDER F I N I SH WTB . 00005 -A
CYLINDER FINISH
Wossner pistons and rings are engineered for high performance and reliability, using premium materials and manufacturing methods. Cylinder finish and geometry are critical to the operation of the piston and piston ring / cylinder interface. The piston ring does require a break in process to have proper seal in the cylinder bore. WTB.00005-A Wossner pistons and rings are engineered for high performance and reliability, using premium materials and manufacturing methods. Cylinder finish and geometry are critical to the operation of the piston and piston ring / cylinder interface. The piston ring does require a break in process to have proper seal in the cylinder bore. Finishing the cylinder wall with a “plateau finish” is the most desirable finish for the best ring function. In simple terms, a plateau finish is a cylinder wall that can hold lubrication well, while also not having a high RA (roughness average). This is accomplished using several finishing steps for the final bore diameter. It is best to use torque plates when available to minimize distortion. Follow best practices to maintain cylinder roundness / cylindricity / taper. The chart below explains what to expect from each finishing step for best surface finish RA values: Finishing the cylinder wall with a “plateau finish” is the most desirable finish for the best ring function. In simple terms, a plateau fi ish is a cylinder wall that can old lubrication well, while also not having a high RA (roughness average). This is accomplished using several finishing steps for the final bore diameter. It is best to use torque plates when available to minimize distortion. Follow best practices to maintain cylinder roundness / cylindricity / taper. The chart below explains what to expect from each finishing step for best surface finish RA values: STEP MATERIAL DISTANCE TO FINISH BORE EXPECTED RA VALUE BORE TO ROUGH SIZE -0.0050 ” (-0.130mm) 75-98 FINISH STEP 1 -0.0020 ” (-0.050mm) 30-35 FINISH STEP 2 -0 .0005” ( -0.013mm) 20-25 FINAL HONE ZERO 7-10 FINISH STEP 1 nd 2 will cre te the urface required t retain oil. The FINAL HONE step will remov the high peaks from the initial honing steps – this is the “plateau hone” step. FINISH STEP 1 and 2 will create the surface required to retain oil. The FINAL HONE step will remove the high peaks from the initial honing steps – this is the “plateau hone” step. The finishes listed above can be accomplished using known honing stone grit numbers, the chart below illustrates expected RA values from common stone grit size available from Sunnen. Note that cutting pressure can greatly affect the resulting RA value: Source: sunnen.com, goodson.com, cylinderheadsupply.com The finishes listed above can be accomplished using known honing stone grit numbers, the chart below illustrates expected RA values from common stone grit size available from Sunnen. Note that cutting pressure can greatly affect the resulting RA value: STONE / GRIT SUNNEN CK - CV STONE CYLINDER MATERIAL APPROXIMATE RA RESULT 220 EHN-512 FERROUS / NICKEL 40 – 48 220 JHU-525 FERROUS / NICKEL 30 – 35 280 JHU-623 ALUMINUM / FERROUS / NICKEL 20 – 25 400 JHU-818 ALUMINUM / FERROUS / NICKEL 10 – 15 600 C30-PHT-731 ALUMINUM / FERROUS / NICKEL 7 – 10 Source: sunnen.com, goodson.com, cylinderheadsupply.com Cylinder cross hatch is important for FINISH STEP 2, as the proper cross hatch angle will provide proper oil retention on the cylinder wall, as well as ring rotation in 4-Cycle engine applications. Cross hatch angles that are too great will shed oil too quickly. Cross hatch angles that are too shallow can cause glazing (not allowing ring seating during break in), as well as slow ring rotation and reduced heat transfer: NOTE: Some aluminum bores require additional honing steps, stone types, and abrasives not listed here Cylinder cross hatch is important for FINISH STEP 2, as the proper cross hatch angle will provide proper oil retention on the cylinder wall, as well as ring rotation in 4-Cycle engine applications. Cross hatch angles that are too gre t will shed o l to quickly. Cross hatch angles that are too shallow can caus glazing (not allowing ring seating during break in), as well as slow ring rotation and reduced heat transfer: NOTE: Some aluminum bores require additional honing steps, stone types, and abrasives not listed here. Always follow your OEM service manual for engine break in, as this is critical to the piston ring seal and ring service life. When in doubt, always check with your dealer or a reputable engine builder for guidelines. Always follow your OEM service manual for engine break in, as this is critical to the piston ring seal and ring service life. When in doubt, always check with your dealer or a reputable engine builder for guide ines. STEP MATERIAL DISTANCE TO FINISH BORE EXPECTED RA VALUE BORE TO ROUGH SIZE -0.0050” (-0.130mm) 75-98 FINISH STEP 1 -0.0020” (-0.050mm) 30-35 FINISH STEP 2 -0.0005” (-0.013mm) 20-25 FINAL HONE ZERO 7-10 STONE / GRIT SUNNEN CK - CV STONE CYLINDER MATERIAL APPROXIMATE RA RESULT 220 EHN-512 FERROUS / NICKEL 40 – 48 220 JHU-525 FERROUS / NICKEL 30 – 35 280 JHU-623 ALUMINUM / FERROUS / NICKEL 20 – 25 400 JHU-818 ALUMINUM / FERROUS / NICKEL 10 – 15 600 C30-PHT-731 ALUMINUM / FERROUS / NICKEL 7 – 10
Cylinder Deck Surface
30° Off horizontal axis
60° Included angle
With proper cylinder finishing you are providing the piston and ring assembly the best opportunity for performance and service.
With proper cylinder finishing you are providing the piston and ring assembly the best opportunity for performance and service
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