Atkinson's work with Crossley raising compression to improve efficiency is interesting. It is often overlooked that reducing the combustion space by increasing compression allows for greater expansion. It also seems they were convinced it was necessary to completely scavenge the cylinder. I wonder how much effect the increased scavenging had on efficiency? Many modern engine are using exhaust gas recirculation (EGR) to reduce NOX emissions. Also this book states that the Connelly engine was a compound engine. I believe that was inaccurate. The Connelly engine was a piston charged 2 stroke (Clerk cycle) similar to a Reid type engine.