The Function of the Ring

What is the real function of the ring?

OK, RINGS?? What are the functions of the piston rings? The most common answer is " To create a seal for compression." OK, the sealing off of the gases for the compression portion of the stroke is a major function of the piston ring, BUT this is not all the ring has to accomplish. Let's look at at what else is going on with the rings.

The style of ring, number of rings, and its location on the piston is very important in assuring that this heat dissipation successfully takes place.

Now, the piston is back at BDC and it all starts over again.

The piston is subject to more abuse then any other part of the 2 stroke engine. It is constantly being pushed on, sucked on, fired on, squeezed on.... well, you get my point.
 
    It is the weakest link in the engine.
 
    Over the last decade or so, advances have been made in piston technology. It has been found that adding Silicon to the Aluminum will reduce piston expansion caused by the extreme heat that is present within an engine. This reduction in thermal expansion reduced piston seizures. Silicone also adds strength to the aluminum and reduces wear.
 
    Pistons are often though of as being a perfectly round cylinder.  In actuality, pistons are tapered from the top to the bottom. Why?... Well, different parts of the piston are subject to different levels of heat and since heat tends to expand metals, then it stands to reason, that the areas which are subjected to more heat will expand more then the areas that are subjected to less heat. The top of the piston is obviously subjected to the most amount of heat, as well as pressure, and therefore; will expand more.
  
    Pistons are not only tapered, but oval ground at the skirt. Once again, this is to accommodate the different temperatures that are present on different parts of the piston.
 
    So, when measuring a piston for wear, one needs to measure on the skirt faces at the widest point which is always below the wrist pin. Measuring anywhere, but the widest point will give an inaccurate measurement.