Scavenge
Scavenge , transitive verb
To cleanse, as streets, from filth. — C. Kingsley
2.
to salvage (usable items or material) from discarded or waste material.
3.
To remove (burned gases) from the cylinder after a working stroke.
Scavenge , intransitive verb
(Internal-combustion Engines) To remove the burned gases from the cylinder after a working stroke; as, this engine does not scavenge well.