Gearhead: Piston Rings

March 25th, 2016 by

Piston rings

Maybe you have, or maybe you haven’t heard of a piston ring. Heck, maybe you’ve never heard of a piston! Well, we’re going to give you some details about what a piston ring does to help make your engine run smoothly.

First, let’s talk about pistons. A piston is one of the moving parts within your car’s engine and there is one piston for each cylinder of your engine. The function of pistons is to create pressure in the engine, which turns into combustion and combustion is what creates the power of your engine. So, pistons play a very vital role in the power and performance of a car’s engine. Pistons are also subjected to extreme pressure and heat.

Here’s a quick breakdown of how some of the pertinent engine parts are associated to each other. The piston rings are on the pistons. The piston is located in the cylinder and multiple cylinders are usually arranged side by side in what is known as a bank. The bank is known as the engine block. 

Now, let’s get into the function of the piston rings and describe how these three rings protect your engine as well as help maintain the performance of your engine.

As the piston travels back and forth within the cylinder, oil is dispensed to lubricate the piston and the cylinder walls. Since the piston is moving at a high rate of speed, friction can create an immense amount of heat and without the oil to lubricate, the metal piston could fuse itself to the metal cylinder wall, stopping the engine — not good.

In the image below, you can see that we have labeled the three rings. The top ring is the Compression Ring. This ring helps keep the pressure within the combustion chamber without letting it “leak” down the sides of the piston. The second ring serves a dual purpose. It too helps keep the compression from sneaking by. Because the rings float within their space, the compressed air can slip by the top ring and sometimes the second ring. This is known as blow by. The second function of the second, or middle ring, is to wipe the cylinder walls and pull any oil back down into the engine, keeping it from traveling up into the Combustion Chamber. The last ring, or lowest ring is strictly there for the purpose of collecting oil from the cylinder walls and returning it to the engine.

As engines get older, piston rings can become worn and the chances of blow by get higher, just because the rings are not as tight as they once were. This can affect the performance of your engine. If a ring were to break, it could cause serious damage to the cylinder and cylinder walls. Unfortunately, inspecting rings is not something that is easy and quite frankly does not make sense. You would need to “tear down”, or take apart, your engine to see these rings and that can be very expensive. If you were to do this, you might as well replace the rings while you have everything exposed.

The most effective way of helping your engine and piston rings last a long time is follow the owner’s manual for regularly scheduled maintenance, including oil changes.

Parts of a piston


Posted in Parts