<P> Regulations of fuel quality vary across jurisdictions . In North America, Europe, Japan and Hong Kong, gasoline and diesel fuel are highly regulated, and compressed natural gas and LPG (Autogas) are being reviewed for regulation . In most of Asia and Africa, the regulations are often lax: in some places sulfur content of the fuel can reach 20,000 parts per million (2%). Any sulfur in the fuel can be oxidized to SO (sulfur dioxide) or even SO (sulfur trioxide) in the combustion chamber . If sulfur passes over a catalyst, it may be further oxidized in the catalyst, i.e., SO may be further oxidized to SO . Sulfur oxides are precursors to sulfuric acid, a major component of acid rain . While it is possible to add substances such as vanadium to the catalyst washcoat to combat sulfur - oxide formation, such addition will reduce the effectiveness of the catalyst . The most effective solution is to further refine fuel at the refinery to produce ultra-low sulfur diesel . Regulations in Japan, Europe and North America tightly restrict the amount of sulfur permitted in motor fuels . However, the direct financial expense of producing such clean fuel may make it impractical for use in developing countries . As a result, cities in these countries with high levels of vehicular traffic suffer from acid rain, which damages stone and woodwork of buildings, poisons humans and other animals, and damages local ecosystems, at a very high financial cost . The catalytic converter should be cleaned four times per year to maximize performance, according to Exhaust Systems Guide . </P> <P> Catalytic converters restrict the free flow of exhaust, which negatively affects vehicle performance and fuel economy, especially in older cars . Because early cars' carburetors were incapable of precise fuel - air mixture control, the cars' catalytic converters could overheat and ignite flammable materials under the car . A 2006 test on a 1999 Honda Civic showed that removing the stock catalytic converter netted a 3% increase in horsepower; a new metallic core converter only cost the car 1% horsepower, compared to no converter . To some performance enthusiasts, this modest increase in power for very little cost encourages the removal or "gutting" of the catalytic converter . In such cases, the converter may be replaced by a welded - in section of ordinary pipe or a flanged "test pipe", ostensibly meant to check if the converter is clogged, by comparing how the engine runs with and without the converter . This facilitates temporary reinstallation of the converter in order to pass an emission test . In many jurisdictions, it is illegal to remove or disable a catalytic converter for any reason other than its direct and immediate replacement . In the United States, for example, it is a violation of Section 203 (a) (3) (A) of the 1990 Clean Air Act for a vehicle repair shop to remove a converter from a vehicle, or cause a converter to be removed from a vehicle, except in order to replace it with another converter, and Section 203 (a) (3) (B) makes it illegal for any person to sell or to install any part that would bypass, defeat or render inoperative any emission control system, device or design element . Vehicles without functioning catalytic converters generally fail emission inspections . The automotive aftermarket supplies high - flow converters for vehicles with upgraded engines, or whose owners prefer an exhaust system with larger - than - stock capacity . </P> <P> Vehicles fitted with catalytic converters emit most of their total pollution during the first five minutes of engine operation; for example, before the catalytic converter has warmed up sufficiently to be fully effective . </P> <P> In 1995, Alpina introduced an electrically heated catalyst . Called "E-KAT," it was used in Alpina's B12 5, 7 E-KAT based on the BMW 750i . Heating coils inside the catalytic converter assemblies are electrified just after the engine is started, bringing the catalyst up to operating temperature very quickly to qualify the vehicle for low emission vehicle (LEV) designation . BMW later introduced the same heated catalyst, developed jointly by Emitec, Alpina and BMW, in its 750i in 1999 . </P>

When were catalytic converters introduced in the uk