Can a new vehicle from a plant be produced without a catalytic converter? Is it possible? I am a lecturer at a college in Zimbabwe, and my students recently asked this question, so I am researching.

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    @RozzA "it is just for converting the 'warming-up' emissions from your engine." Are you sure about that? Wikipedia says, essentially, the exact opposite: that most of the emissions from cat-fitted cars come in the first few minutes because the cat is ineffective until it's warmed up enough. And the whole point of a catalyst is that it isn't used up: it merely facilitates a chemical reaction. So the other claim in your comment sounds very dubious, too. Jun 5, 2019 at 21:28
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    @RozzA Not true - catalysts do not get "used up". It certainly is possible to poison a catalyst with leaded fuel, but that only needs a few trips at most to kill the cat. Most countries following CARB, EURO or similar emissions rules require regular emissions tests, and it simply is not possible to meet those emissions standards without a cat and any other related emissions control devices. FYI, I'm an ex automotive software engineer who's spent far too many years dealing with emissions and diagnostics specifications!
    – Graham
    Jun 5, 2019 at 22:28
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    @Paulster2 Remarkably trusting of them. In the UK they stick a probe up the exhaust. Of course it doesn't catch everything, but it reduces the options for cheating, at least for petrol (gasoline) - diesel emissions are mostly particulates and can't be tested so easily. As for "all you have to do", it's not necessarily easy to do that (depending on the ECU of course), or at least to do it in a way which the tester won't pick up.
    – Graham
    Jun 6, 2019 at 1:06
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    @RozzA no, that's just some nonsense made up by hotrod types to rationalize hacking the cat off the car... My cat was effective for at least 15 years... Jun 6, 2019 at 14:23
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    @CarlWitthoft No, but your power plant probably does! Jun 7, 2019 at 15:30

4 Answers 4


You don't have to have an catalytic converter, they aren't required for the operation of an engine. Catalytic converters use chemical reactions to reduce the pollution in internal combustion engine exhaust, and are emissions control devices which are required by regulation in many countries. So it's technologically possible to build a car without one, it just may not be legal depending on where you are.

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    On top of that, electrical cars do not need one (for obvious reasons) and most marine engines also do not always require one
    – Horkrine
    Jun 6, 2019 at 12:56

That will depend on the market regulations for the target country ie which country that vehicle will be sold in.

Cars built to be sold in Europe & US have to meet stringent regulations as regards emissions so they are required to have a catalytic converter.

Other countries may not (yet) have that requirement, so a "cat"may not be necessary.

The large car manufacturers have been known to "use" this - when tighter emissions legislation came in in the Eu, some car manufacturers had stocks of engine that were no longer fit for the EU market. These were then sold in other markets...

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    Of course the other answer to "Can a vehicle from a plant be produced without a cat" can be answered "Yes, an electric vehicle" (or a vehicle such as a racing go-kart) Jun 5, 2019 at 12:14
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    @SteveMatthews you can fit a cat to an electric vehicle - as an ornament... Are some countries starting to require smaller engines go-karts, lawnmowers etc to meet higher emissions standards?
    – Solar Mike
    Jun 5, 2019 at 12:15
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    @SolarMike: I know california has strict requirements for small engines, I'm not sure if it expands to requiring cats but their emissions are certainly a factor.
    – jesse_b
    Jun 5, 2019 at 18:44
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    @SolarMike Even my 25-cc weed whacker has a cat in the US, it's a platinum coated mesh in the muffler. As Jesse_b mentions, it's because California is so sunny, they have photochemical smog problems.
    – user71659
    Jun 5, 2019 at 20:52
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    @user71659 And because of the geography of Western California, with mountains on one side and ocean on the other. This means that when photochemicals show up, they don't really have anywhere to go and so tend to accumulate into worse (more dense) smog than you would get in other places. Jun 5, 2019 at 21:00

Yes, in theory. The government doesn't care how your engine hits the required emissions numbers. As an engine designer, you get a tabula rasa, and are free to build any system that will do the job.

Catalytic converters seem to be a winning choice for most if not all engine builders, because engine building is largely a costing game and cats are the easiest way to hit a price point. A big part of why they hit a price point is that they are already mass produced and readily available both in prototyping and in mass production at scale.

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    Given their hobby to go against the market mainstream in almost everything, if it were possible to fulfill exhaust gas limits without a catalytic converter, Mazda would already be doing it :)
    – Pavel
    Jun 7, 2019 at 9:16

No Telsa has a cat. While you could bolt one to a Tesla it would serve no purpose.

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    Even the Tesla may serve no purpose! whereisroadster.com No catalytic converter on the boosters, either.
    – Bob Kerns
    Jun 6, 2019 at 12:50
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    "No Tesla has a cat." <sup>citation needed</sup> ;) Jun 7, 2019 at 15:33
  • @DonBranson Catalytic converters are for internal combustion engine cars. Teslas are battery powered, no internal combustion engine. Jun 7, 2019 at 16:03
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    @LorenPechtel - I know, thanks. You probably missed the wink at the end. Jun 7, 2019 at 16:07
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    @DonBranson Sorry, I've been asked for evidence of the obvious so many times over the years that I failed to note yours was a joke. Jun 8, 2019 at 17:09

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