Because that is how they are made to run. They were added to cars to cut smog emissions and meet federal/state standards. Lead ruins the catalyst in the converter.
No, diesels can and do have them also.
catalytic converters
Catalytic feedback includes reviews of catalytic converters. A catalytic converter is fitted to your car's exhaust to reduce the harmful pollution coming from it.
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Any vehicle built since 1975 has a converter installed.
In UK, all new cars from 1992 had to have a catalytic converter fitted, which required a strict diet of unleaded fuel. Many had 'cats' fitted as standard well before then.
catalytic converter
Yes, It is directionally specific. It should be fitted in the right direction or it will perform its function perfectly.
They capture harmful emissions that would otherwise be released into the atmosphere.
The gas that's emitted from rotting eggs is hydrogen sulphide. this is what gives both eggs and cars fitted with catalytic converters the smell
Catalyctic converters super heat the exaust of the engine to temperatures from 2000-2400 degrees and burn off exaust gasses and make the exaust cleaner. They have pellets in them that scrub the exaust. This reduces the vapors that produce acid rain.
Australia has had road vehicle emission standards for new vehicles in place since the early 1970s and these have been progressively tightened over the past 45 years. Because of that, catalytic converters were found to provide an answer to the control of emissions and to provide compliance with the regulated emissions standards of the day. It appears there is no law that says a cat must be fitted but a passenger vehicle must however comply with the emissions requirements and cats can provide the answer. i.e. there could be something else that could do the job, once discovered.