<div class="htmlview paragraph">In the previous reports (SAE PAPER <a href="http://www.sae.org/technical/papers/880268" target="_blank">880268</a>, <a href="http://www.sae.org/technical/papers/900223" target="_blank">900223</a>), 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).</div> <div class="htmlview paragraph">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.</div> <div class="htmlview paragraph">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.</div> <div class="htmlview paragraph">It was found that the proposed empirical formula for Pmf is applicable to high revolution engines which run up to 20,000 rpm and that a reduction in Pmf can be achieved by utilizing an engine with short-strokes, multi-valves and multi-cylinders.</div> <div class="htmlview paragraph">Under optimum operating conditions, the values of modified indicated mean effective pressure (Pmi*) [≡ (Pmf + Pme) / (κ(ε)ηυ)] have shown to be substantially constant and agree well with the value of modified Pmi̅ (Pmi̅*) which is obtained from the indicated pressure diagrams of 300 cycles under same optimum operating conditions.</div> <div class="htmlview paragraph">Therefore, it is concluded that net output (Pse) can be also estimated at planning stage of a new engine layout with the value of ηv calculated numerically, the constant value of Pmi* and the value of Pmf calculated from the empirical formula.</div>