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Piston ring radial pressure effects both the manufacturability of the ring as well as its performance in the engine. While lack of radial contact can cause increased blow-by and lubricant oil consumption, high local contact pressure can cause excessive wear and even scuffing. Current methods to evaluate ring radial pressure fail to identify subtle, local pressure changes. To overcome such limitation, a new method to evaluate ring radial pressure at each peripheral angle was developed. In this experimental procedure, the ring free shape is recorded by an optical device and then this free shape is used as input to code that calculates its radial pressure distribution. In order to validate this method, six different sample variants of ring pressure distribution, (i.e. free shape), have their radial pressure evaluated by two different methods: 1,) the new procedure and 2,) a mechanical jig with 11 circumferentially spaced radial load sensors.

Engine developments have led to higher mechanical and thermal loads on the components, at the same time that lower friction losses are also sought. Therefore, the development of better materials and of surface treatments has received great emphasis. This paper presents the results of dynamometric engine tests with a proposed piston ring pack, composed of a gas nitrided steel top ring, a nitrided gray cast iron second ring and a normal production chrome plated oil ring. The proposed pack showed very low wear when applied to a medium duty diesel engine, besides being a cost-effective alternative to the conventional pack with moly coated and chrome plated (respectively in the top and second) rings. The proposed pack also caused very low wear on the cylinder bore, specially near the TDC, where the bore wear is usually maximum.