The fresh air intake pathway in the 4-cycle FRE and the high pressure intake pathway(s) in the 2-cycle FRE is always unobstructed and direct to the VVC (working chambers) in the engine's annular cavity intake regions.

The FRE exhaust gas pathway(s) extend from the VVC in the exhaust region(s) of the [engine's] annular cavity to outside the engine and are also always unobstructed.

The complex ignition systems required in other internal combustion engines types are not needed in FRE;
i.e.  FRE do not need a multitude of ignitor plugs, coils, complex ignition wiring, distributors, distributor drive elements, and the structural support configurations required for their function.

Only a primitive ignitor is require to initiate combustion in the FRE.

Once initiated, combustion is self perpetuating in a FRE.

Combustion is initiated in each FRE VVC (working chamber) as soon as injected fuel is available.

The flow of combustion involved hot gases under pressure through the gap at the partition separating the VVC being fuel injected from its combustion involved neighbor VVC effects the ignition of the injected fuel.

Fuel is supplied to the FRE VVC by relatively simple throttle controlled steady flow injection.

Both liquid and gas fuels may be used to fire FRE.

Instead of using a complex high pressure sequential fuel injection system with high pressure metering and injection subassemblies and injectors at each working chambers typical to other engine, the FRE has fuel injected into the its VVC (working chambers) via a steady flow through a single injector nozzle (set) located in the rotor.

As each VVC traverses the fuel injector's rotor location it intercepts the injector's steady fuel stream.

This continuous fuel injection characteristic of the FRE permits the vaporization of liquid fuels by exhaust gas heat prior to injection so that the liquid fuel enters the VVC as high pressure combustible vapor.

This type of liquid fuel handling system eliminates the very high liquid fuel injection pressures required in other fuel injector systems to attain proper fuel droplet size for proper combustion.

There are no wiping (wiping abutments) or fixed seals between the relatively moving parts of FRE working chambers (the VVC);
i.e.  A FRE does not have wiping and sealing abutments (e.g. piston rings, valve seats and keeps) in the environment extremes of temperature and pressure required in other internal combustion engines.

The FRE has no need for pressure rings, oil barrier rings, valve to valve seat sealing, valve keeps, etc. or their supporting engine structures.

Therefore, parts wear, inter part heat transfer and mechanical stresses are greatly reduced in FRE.

The lack of wiping abutments in the FRE also permits a less expensive use of high temperature engineered ceramic materials.

Machining tolerances are larger and the use of ceramic materials permits higher and more efficient engine operating temperatures.

For the environmental agency regulation constrained engine designer, most FRE designs can accommodate fresh air purging intake(s).

The purging air intake is used to supply sufficient air to the VVC in the annular cavity exhaust region(s) to complete combustion of the exhaust gases during their purge, to eliminate residual exhaust gases in the VVC and to cool the VVC.