&gt; Sounds like they&#x27;re trading the spark system (a pretty easy to maintain system) for a second piston&#x2F;crankshaft&#x2F;etc.<p>Opposing pistons and compression ignition are (mostly) orthogonal optimizations. From years of working on engines, I&#x27;d also be more willing to call the mechanical parts &quot;perfected&quot; and the ignition system &quot;not perfected&quot;, at least for common consumer engines.