It looks like Mazda sees high compression-ratio engines as the way forward to boost fuel economy and specific power on their midsize gasoline engine lineup (13:1 is an impressive achievement).

According to their [promotional material](https://youtu.be/rNtS8qyjIJU) they reduce the risk of detonation by reducing the temperature of the intake charge. This is done by designing longer exhaust runners in an attempt to eliminate the possibility of hot exhaust gases reaching the intake valves of other cylinders.

Does this mean that exhaust gas recirculation is avoided altogether? If so, what implications would this have on the design of the catalytic converters?