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Many two stroke engine for hand-held applications are equipped with muffler that contain a catalyst in order to reduce emissions. However, one of the main problems, is to mantain the performances of the catalyst over time; this often leads to the adoption of systems with increased culling oversized issues related to weight, dimensions and temperature. One of the major causes of degradation of the catalyst is derived from elements of poison present in the oil mixture. This study showed the results obtained by comparing different types of oils of mixture, through durability tests carried out on an engine of a brush cutter.

The improvement in engines efficiency and reduction of emissions is the permanent aim of engine industry in order to meet European standards regulation. To optimize small internal combustion engines it is necessary to improve the basic knowledge of thermo-fluid dynamic phenomena occurring during the combustion. This paper describes the combustion process in an optically accessible two-stroke spark-ignition engine used in a commercial 43 cm3 chainsaw. Two different feeding systems were tested: standard and CWI one. The engine head was modified in order to allow the visualization of the combustion using endoscopic system coupled with a high spatial resolution ICCD camera. Flame front propagation was evaluated through an image processing procedure. The image visualization and chemiluminence allowed to follow the combustion process from the spark ignition to the exhaust phase at high engine speed. All the optical data were correlated with engine parameters and exhaust emissions.