Aftermarket exhaust parts and the engine. However, the pipes do "ring" with the exhaust pulses and increase underhood noise. Headers can be ceramic coated to reduce the heat radiated in the engine compartment, and to increase the temperature of the pipes which increases the velocity of the exhaust gases. Terminology: Catalytic converters are necessary to reduce emissions but create back pressure due to the exhaust gases being forced through a catalyst, and therefore decrease high-end engine power. Many modern catalytic converters only produce 1-3 psi of back pressure, though this restriction worsens further with use. Hi-flow catalytic converters can replace the standard units
Steam car steam engine conversions for existing production cars. When air pollution became a significant issue for California in the mid-1960s the state encouraged investigation into the use of steam-powered cars. The fuel crises of the early 1970s prompted further work. None of this resulted in renewed steam car manufacturing. Steam cars remain the domain of enthusiasts, occasional experimentation by manufacturers, and those wishing to establish steam-powered land speed records. In 1967, California established the California Air Resources Board and began to implement legislation to dramatically reduce exhaust emissions. This prompted renewed interest in alternative fuels for motor vehicles and a resurgence