For every cycle and construction, there is theoretical efficiency limit inherent to it. Implementations will approach that, more or less asymptotically, but can't exceed.
A novel cycle and construction may leave more headroom for improvement, even if first implementation aren't particularly efficient.
IIRC turbines are usually highly efficient, but only in a narrow band, near maximum output; at low RPM they literally suck. Perhaps a novel construction could widen the gap considerably.
That's correct , but its possible that the time has come when narrow-band-efficiency is an appropriate technology.
A "typical" car with a piston engine directly mechanically connected to the wheels needs an engine with a wide rpm and power output range.
A hybrid electric drivetrain doesn't necessarily need that - if a motor that could run at 60% efficiency but only at 8725 +- 15 rpm existed, it'd be useless for a traditional car, but it'd be easy to integrate that into a hybrid electric vehicle...
A novel cycle and construction may leave more headroom for improvement, even if first implementation aren't particularly efficient.
IIRC turbines are usually highly efficient, but only in a narrow band, near maximum output; at low RPM they literally suck. Perhaps a novel construction could widen the gap considerably.