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The high temperature tribology issue for uncooled Low Heat Rejection (LHR) diesel engines where the cylinder liner piston ring interface exceeds temperatures of 225°C to 250°C has existed for decades. It is a problem that has persistently prohibited advances in non-watercooled LHR engine development. Though the problem is not specific to non-watercooled LHR diesel engines, it is the topic of this research study for the past two and one half years. In the late 1970s and throughout the 1980s, a tremendous amount of research had been placed upon the development of the LHR diesel engine. LHR engine finite element design and cycle simulation models had been generated. Many of these projected the cylinder liner piston ring top ring reversal (TRR) temperature to exceed 540°C[1]. In order for the LHR diesel to succeed, a tribological solution for these high TRR temperatures had to be developed.

High unburned hydrocarbon emissions and poor fuel consumption arise in a carburetted two-stroke engine because of its scavenging process. Time resolved hydrocarbon concentration at the exhaust port has shown a definite trend in concentration of unburned hydrocarbon with respect to crank angle. This paper discusses an exhaust gas recirculation system designed to trap fraction of the exhaust gas that is rich in short circuited fresh charge. In this design, the differential pressure between the crankcase and the exit at the exhaust port is communicated with each other at the appropriate time through passages in the piston and the cylinder block. The design is thus capable of selectively trapping and recirculating fraction of the exhaust gas rich in short circuited fresh charge back into the cylinder for combustion.