Unfortunately I could not find a Napier Nomad in the RAF museum
but they did have the precursor engine called
Sabre III. The turbo compound Nomad holds the worlds record
for the most efficient internal combustion engine ever built.
Like the Wankel rotary engine it had no conventional poppet exhaust
valves with the associated kinetic energy losses. Like the Sabre the Nomad
had sleeve valves.

Paul Lamar In London