Exhaust system Law in the United States and other countries to not have a catalytic converter. Converters may not be removed from a vehicle that is used only for "off-road" driving in the United States. The main purpose of a catalytic converter on an automobile is to reduce harmful emissions of hydrocarbons, carbon monoxide and nitrogen oxides into the atmosphere. They work by transforming the polluted exhaust components into water and carbon dioxide. Cat-back (also cat back and catback) refers to the portion of the exhaust system from the outlet of the catalytic converter to the final vent to open air. This
Exhaust system tandem with smog abatement legislation rendered lake pipes, as a bona fide performance prerequisite, obsolete. No meaningful performance gain to be had for contemporary vehicles, lake pipes persist into the 21st century as a superfluous, retrograde aesthetic, usually chrome plated with various options, allowing the driver to control whether exhaust gas is routed the standard exhaust system, or through lake pipes, which are commonly fashioned by laker caps which, affixed by fasteners at the terminal end of exhaust tips, serve to (1) "cap" the exhaust system when not in use, and/or (2) signal authorities that the presence of lake pipes