Gapless rings are another hotly debated issue in the engine building community. Some swear by them, others swear at them.
The theory of gapless rings is understandable, no gap, no compression loss by the rings. according to some, it is not that simple. The top ring on a gasoiline engine should be doing the combustion gas retention the second ring is more of an
oil control ring to wipe the cylinders clean. The
oil ring is designed to distribute the
oil to the cylinder wall. Most gapless rings are installed in the second ring land. Some say that the gapless second ring creates a low pressure area ( no Turk, not that kind of low pressure area, it won't rain inside your cylinders
) which causes the ring to "flutter" in the ring land which will eventually wear the ring land and cause poor ring seal. Some piston manufacturers cut a groove between the 1st and 2nd rings in an attempt to equalize the pressure between the rings. The contention is that when the engine is static and a leak-down test is done the leakage numbers are very low, from 0 to 3 percent. But, when the engine is running, the rings "move around", causing poor cylinder sealing. There are new design gapless rings coming that are suppose to address this issue. Ring sealing is a constantly evolving science and new ideas and theories a coming all the time.
HTH,
Mike
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