DIFF Subgroup
F01B 1/0641 Full Title
Reciprocating-piston machines or engines characterised by number or relative disposition of cylinders or by being built-up from separate cylinder-crankcase elements (F01B3/00, F01B5/00 take precedence) > with cylinders in star or fan arrangement
Of 7 combined children, 0 exist in both systems.
7 codes are CPC-only extensions.