LO 7-5 Identify and explain the purpose and functions of piston rings, their construction features, and their ring shapes according to ring function

LO 7-05: Identify and explain the purpose and functions of piston rings, their construction features, and their ring shapes according to ring function.

Exhaust Gas Recirculation and Piston Ring Longevity

Refinements to ring design, cylinder bore finishing techniques, and engine oils have helped produce engines that can operate for thousands of hours and more than 1,000,000 miles (1,609,344 km) of use before the piston rings may need to be replaced. Ring design and the performance of engine oil are even more critical with the use of EGR-equipped engines. Higher cylinder temperatures and pressures, combined with the reintroduction of soot and corrosive exhaust gases found in recirculated exhaust gases, can affect ring longevity Figure 28. Diesel EGR rates are more than three times that of gasoline- fueled engines. For this reason, ring technology has changed to compensate for this newer engine wear factor. New materials (such as alloyed steel or ceramic-faced rings) and manufacturing techniques (such as plasma-sprayed ring faces) have produced some of the most sophisticated and durable rings ever made.

FIGURE 07-28: The use of EGR reintroduces soot, an abrasive compound, back into cylinders.

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