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
Diesel exhaust U.S. 2010 emissions criteria, selective non-catalytic reduction (SNCR), and exhaust gas recirculation (EGR). Both are in the exhaust system of diesel engines, and are further designed to promote efficiency. Selective catalytic reduction (SCR) injects a reductant such as ammonia or urea — the latter aqueous, where it is known as diesel exhaust fluid, DEF) — into the exhaust of a diesel engine to convert nitrogen oxides (NO) into gaseous nitrogen and water. SNCR systems have been prototyped that reduce 90% of the NO in the exhaust system, with commercialized systems being somewhat lower. SCR systems do not necessarily need particulate