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In the previous reports (SAE PAPER 880268, 900223), a relationship between dimensional specifications and total engine loss (Pmf) measured by motoring method under certain conditions was established by analyzing 300 different types of mass-produced engines of which engine speed for maximum power output (Nepsmax) was obtained between 8,000 and 16,000 rpm, and thereby an empirical formula was proposed (Pmf). In this paper, it is proved that brake mean effective pressure (Pme) can be estimated by using the empirical formula for Pmf and modified indicated mean effective pressure (Pmi*) obtained from analyzing various types of motorcycle engines consisting of different cylinder configurations, valve sizes and numbers. At first, the relationship between the characteristic values of engine and Nepsmax is described, and methods to obtain higher power output by increasing engine speed are also discussed.

Honda has produced high-speed, high-performance, 4-stroke cycle gasoline engines by applying advanced technology gained through the design and development of motorcycles and automobiles for Grand Prix racing. Some of Honda's racing engines attained performance as high as 260 bhp/liter or nearly 4.3 bhp/cu in. at speeds of up to 25,000 rpm. This paper describes our technical approach for optimizing combustion efficiency, volumetric efficiency, and mechanical efficiency-the keys to high-speed, high-performance engines.

Many papers are written on the frictional loss of each component in an engine, such as piston, crankshaft or bearings, but few papers describe on the total engine friction in detail. In this paper, the total engine friction is analyzed using the engine friction data of 145 HONDA mass produced motorcycle in-line engines, including single-, 2- and 4-cylinder configurations measured by the motoring method. Consequently, it is shown that the total engine friction, that is the frictional mean effective pressure (Pmf), is mainly influenced by the following dimensions; cylinder bore, piston stroke, crank pin and journal diameters. Thus the empirical equation for the total engine friction is derived, and it becomes thereby possible to reduce the total engine friction as well as to estimate it.