Proton, the conditions you mentioned were also mentioned in one of my sources. The Japanese seemed to always have difficulties with developing higher powered engines. If one thinks about it, the best designs in WW2 all had outstanding engines. Having said that, I have read that captured Zekes tested by the US seemed to have been well constructed and the engines were reliable in that particular model. One thing we know is that the Japanese know how to build reliable and powerful engines today at least in autos.