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The opposed-piston two-stroke engine (OP2S) notion was first developed in the late 1800s. A keen and rapid development was noted in the first half of the 20th century across many countries for wide range of applications, and its promising fuel efficiency attracted the interest of automotive industry. Unfortunately, severe regulations on emissions led to a discontinuance of OP2S engines despite its high-efficiency. The aim of this project is to model and simulate a simple single-cylinder two-stroke opposed-piston engine and minimise fuel consumption and heat loss, using the software programme AVL BOOST. AVL Boost is an engine modelling platform, which analyses the performance of a modelled two-stroke opposed-piston engine by changing desired parameters. In order to meet this aim, the experimental results from a unique prototype PAMAR-4 engine are used to make a comparison with the results obtained from AVL BOOST model. A validation of this comparison will be produced looking at the compression ratios. Six combinations of compression ratios (12, 13.5, 15, 16.5, 18 and 19.5) are analysed in this study with the engine speed running at 420 rpm and 1500 rpm. In addition to the compression ratios, the effect of stroke-to-bore (S/B) ratios on OP2S performance is investigated. Various values of S/B ratios, whilst maintaining a constant swept volume, and their effect on fuel consumption and heat loss are analysed in this study. A comparison between the two engine speeds with increasing combinations of compression ratios revealed the followings for the 1500 rpm simulation: higher peak pressure; higher peak temperature; reduction in heat loss; higher indicated power; and higher mechanical and indicated efficiency. Detailed analyses of these parameters are highlighted in discrete sections of this paper. Keywords: opposed-piston 2-stroke, AVL Boost, compression ratio, stroke-to-bore ratio