Piston ring
On the other hand, a large gap would cause insufficient sealing of the piston rings against the cylinder walls, resulting in excessive blow-by (combustion gases entering the crankcase) and less pressure on the piston, reducing the power output of the engine.
The sliding motion of the piston ring inside the cylinder wall causes friction losses for the engine.
[3][4] The design of the piston rings is therefore a compromise between minimising friction while achieving good sealing and an acceptable lifespan.
Lubrication of piston rings is difficult and has been a driving force to improvements in the quality of motor oil.
It is important that rings float freely in their grooves within the piston, so that they can stay in contact with the cylinder.
[citation needed] Sealing is often achieved by multiple rings, each with their own function, using a metal-on-metal sliding contact.
The gap in the piston ring compresses to a few thousandths of an inch when inside the cylinder bore.
The revised piston ring was manufactured to an out-of-round shape, so that it would exert even pressure once installed in the cylinder.
To minimize this, they are made of wear-resistant materials, such as cast iron and steel, and are coated or treated to enhance the wear resistance.
A) Rectangular section
B) Barrel face
C) keystone
D) Torsional twist
E) Taper face
F) Dykes
Which also differ for the type of retainer band:
Y) Behind-band
X) Above or under-band
Or for the ends that work without firm stops:
K) Step
J) Oblique
W) Oblique with step
