Fluid working reciprocating devices are described, including internal combustion engines, compressors and pumps, and how such devices may transfer power to electric generators or turbines. Devices can be within casings which may be “snapped into” larger machinery, such as vehicles, aircraft or marine craft. A number of arrangements for pistons and cylinders of unconventional configuration are described, mostly intended for use in IC engines operating without cooling. Included are toroidal combustion or working chambers, some with fluid flow through the core of the toroid, a single piston reciprocating between a pair of working chambers, tensile valve actuation, tensile links between piston and crankshaft, energy absorbing piston—crank links, crankshafts supported on gas bearings, cylinders rotating in housings, injectors having components which reciprocate or rotate during fuel delivery. In some embodiments pistons may rotate while reciprocating. High temperature exhaust emissions systems are described, including those containing filamentary material.