There is this guy who has made some similar engine prototypes in this field of efficient opposed piston engines.<p>PatOP: Single-Crankshaft Opposed-Piston Engine<p><a href="http:&#x2F;&#x2F;www.pattakon.com&#x2F;pattakonPatOP.htm" rel="nofollow">http:&#x2F;&#x2F;www.pattakon.com&#x2F;pattakonPatOP.htm</a><p>OPRE: Opposed piston Pulling Rod Engine<p><a href="http:&#x2F;&#x2F;www.pattakon.com&#x2F;pattakonOPRE.htm" rel="nofollow">http:&#x2F;&#x2F;www.pattakon.com&#x2F;pattakonOPRE.htm</a><p><pre><code>  &gt; A 500cc two stroke can easily make some 80 Nt*m (8 Kp*m) torque.
  &gt; At 6000 rpm this torque makes some 50 KW (70 PS).
  &gt; 50 KW from 20 Kp means 0.4 Kp per KW.
  &gt; And 0.4 Kp&#x2F;KW with direct injection Diesel efficiency sounds interesting, especially for an engine with such a low cost.&quot;</code></pre>