Catalytic Converter: How It Works | Science Garage

Catalytic Converter: How It Works | Science Garage

– Catbacks, resonators, straight pipe. Today, we’re not talking
about any of those things. We’re talking about the
catalytic converter. A catalytic converter is designed to reduce harmful emissions. (coughing) In another video, we
talked about how gasoline is made up of hydrocarbons. If everything goes perfectly,
all of the hydrogens and all of the carbons
combine with all of the oxygen to give us carbon dioxide and water. No big whoops. But the combustion in
an engine isn’t perfect. Some of the reactions are incomplete. And because of the heat in the engine, we create some molecules
that don’t normally occur. So one thing we get is carbon monoxide. It’s bad. It gets rid of the ozone layer. – Shit – And it’s also poisonous. – (beep) – The heat of the combustion
means that some of the nitrogen, because it’s 78%
of the air, gets jacked up and bonds with oxygen in
any number of combinations. And that’s also bad for your health, and it makes our rain acidic. It’s just bad news. – Hey, that’s tough. – And lastly, if some fuel isn’t burnt, those harmful hydrocarbons
get shot out the tailpipe too. (engine revs) Catalytic converters
are designed to reduce all three of these emissions. And the first one was patented by French chemical engineer, Eugene Houdry in 1950. We talked a little bit
about catalysts in our video on tires, and you can
check that out right here. Most basically, a catalyst is something that helps a reaction take place. The things in here act as a catalyst to help convert your
emissions to make them safer. You see what I did there? (maniacal laughing) Catalytic converter. Alright, so what’s in here? There’s ceramic. That doesn’t react with
anything, but it gets super hot, and it stays super hot so
the reactions can happen. If you’re going for an emissions test, make sure your catalytic converter’s hot. Next, there’s rare metals,
platinum, palladium, and rhodium that react with the emissions. They’re each worth about $30
a gram, and there’s between three and seven grams of them
in a catalytic converter. So that’s why people steal them. But, the metal in a
converter is worth about as much as a catalytic
converter, so don’t be a jerk. First is a reduction catalyst. Platinum and rhodium pull
oxygen off the nitrogen atoms so the nitrogen gets
shot out as benign N2, the way it came in in the first place. The second stage is an oxidation catalyst. Platinum and palladium
use the oxygen molecules in the exhaust, and the freed up oxygen from the first stage in two ways. First, it helps bind them
to the carbon monoxide to get CO2, the same
stuff you breathe out. And second, this stage
converter will oxidize any unburnt hydrocarbons
as they pass through. Some cars have a pre cat
closer to the engine. It’s still a catalytic converter, but because it’s so close,
it gets hotter quicker and it does a super
duper job at converting, but because it gets hotter,
it can wear out faster. The oxygen sensor before
the cat lets your car know if there’s enough oxygen
burning the fuel in the engine. If too many hydrocarbons come through, a computer will adjust to mix accordingly. Another oxygen sensor after
the cat let’s your engine know if it’s pulling in enough oxygen to complete the reaction in the converter. It’s all super high tech
and it happens super fast. So do catalytic converters
rob you of horsepower? (gasping) Before we answer that, let’s cut it open. (sawing) (metal clanging) (pounding) (sawing) Inside, you can see the honeycomb, and if I hadn’t beaten the crap out of it with that angle grinder, we’d
have nice clear channels. And you can still see light through it. (whistling music) (air whistling) This is a good cat. (cat meowing) These chambers are designed to have the most surface area possible
to make the reactions happen. They’re also designed to
affect the exhaust flow as minimally as possible. Some brain trust cut these honeycombs out to open up the airflow, so
that when they get inspected, it looks like they still got one. But cutting these out means
the air is suddenly sitting in a big hollow chamber,
instead of shooting straight down a streamlined pipe. Cars are an intricate system
of computers and tuning, and unless you’re skilled
at this type of thing, just ripping out a part of your exhaust, that can seriously damage your car. Modern catalytic converters
are designed to be efficient. There’s even performance
catalytic converters that have been shown to
help improve horsepower. The main thing is that
catalytic converters work. American emission pollutants have dropped an average of over 70%. That’s a big deal. And when you look at
pictures of any major city, before and after we started using them, it’s equally as easy to argue
that the catalytic converter is one of the most important advancements in automotive history. Subscribe to Donut. If you liked watching this
video, please share us. The more we grow, the more
cool stuff we can do for you. Follow me on Instagram @bidsbarto. Follow Donut on Instagram @DonutMedia. If you wanna have a bad ass
car, check out Tony’s video on performance mods that actually work. You like speed? Check out this video on F1. Don’t tell my wife I took the catalytic converter off the car.

About the Author: Michael Flood


  1. Placement of these units needs to be improved to prevent road side fires caused by them witch harms the environment.

  2. At first you mention Rubidium as metal in a catalytic converter and then Rhodium, which is the one that is commonly used?

  3. This fucking cata was about damaging my engine
    I deleted it from my engine
    I don’t give a fuck about pollution
    I’m paying the bills not the nature

  4. Great video, shame about the unnecessary swearing inserts early on. Not good for younger kids who might be interested in the subject.

  5. I cant find a good one for my supercharged cobalt ss, its all catless bullshit that sounds like a honda civic

  6. would be cool if they could figure out some way to use the heat generated by the catylitic converter to porwe up the battery or something.

  7. I've never heard of straight pipe, this is amazing I live in California. Will keep looking for straight pipe videos.

  8. Great intro because its so real.
    Some scientific chemistry speak – "the nitrogen just gets all jacked up", LOL.

  9. It depends where it is, I ripped them out of a BMW where they were a one piece with headers welded just 2 inches from the engine head creating reduced exhaust flow drastically reducing performance. Now put a gas mask on and run and tell us how better for you it is wearing it and running. They are not even made by the manufacturer of your engine, your engine was created and tested without them it was then the green neocon mob came and required to put them on, thats the story how you got them there.

  10. Catalytic converter and unleaded gasoline both make air cleaner. Automobile number have multiplied in numbers since the mid 70's. Automobile still produce lot of toxins.

  11. I watched this in my 9th grade science class and was so fucking happy as i had discovered donut a couple weeks earlier

  12. To anyone feeling like their dealership or the manufacturer is ripping them off, please read this in its entirety. It may be long, but the details matter, and there is maybe a books worth, so I’m trying hard to stay on point and the suspension thing is a perfect example of how they work.
    Here’s a question I’ve been looking for an answer to for about a year. Please if anybody has any legitimate input let me know.
    Does or can the catalyst “swell” or “expand” when it gets hot, and then “shrink” or “contract” when it cools? No obviously we all know that things do that with heating and cooling, but not that much. Can this occur with enough difference that when it swells it can block the exhaust and cause enough back pressure to make a modern car shut off suddenly? And when it shuts off, can it shrink back to normal size within a few seconds, maybe 10 seconds, or even 30? Oh, and all the while no issues with mileage or horsepower, and this happened in a very random manner. I was told that my cats on my 2006 Dodge Magnum RT (Hemi V8) needed replacing (@160,000miles), as well as oxygen sensors and plugs(that were only 50,000miles old) and coil packs. All of this after the engine light came on and it ran a little rough sometimes but not too badly. No loss of power, no mileage degradation, no running hot from backpressure, no sulfur smell from exhaust, no rattle from the cats, all of which I had learned were various symptoms of a bad catalytic converters. Trust me, I thought I knew cars well enough to call bullshit on this swelling and shrinking assessment. Long story short, I’ve got a Lifetime Bumper to Bumper Chrysler Warranty on my car that I purchased when offered, upon my factory warranty running out. Also I’ve had this car ONLY serviced at this dealership where I bought the car brand new, or at the sister dealership across town, but mostly at this one. They’ve stonewalled me on things that seemed at the time to be inconsequential, and also at the time I got sick of complaining about all of the suspension racket from beneath the car. Even though I asked them to look at it almost every time I took it in for service, they almost always said they could t find anything. Now I know that I was right the whole time and that they were just lying. I wasn’t just complaining about superficial noise either. At times you could feel things moving around when I backed out of a driveway for instance. Sometimes the front tires would “scrub” when turning at slower speeds because the two front tires were traveling in different arcs than the ones they were designed to follow. Once the service manager told me that he and a tech took it for a test drive and they discovered rocks inside the rear bumper and they couldn’t be removed “without a whole process which would be a royal pain in the but”. Rocks in my back bumper? As the source of all of the suspension noise. I have restored many an old car and am proficient at getting rid of squeaks, rattles, clunks, etc. It often sounded like an old coffee can with a handful of bolts in it whenever I hit almost ANY bump in the road, cracks, expansion joints, etc, utterly ridiculous, and so loud and noisy I was embarrassed to have passengers, cause it sounded like a 1982 Crown Vic which had never had a single suspension component replaced and was parked in saltwater puddles and driven for thirty years on tank trap type streets. It was actually worse than that. And on and on. That was just to set the stage for treatment. So they told me I needed to replace these things and I would generally have no problem with letting them do their thing as I just pay a $100 deductible. So the story was that the code indicated a misfire condition(notoriously inaccurate because other things can set off that code) which COULD have sent unburied fuel into the cats and ruined them. Now from what I understand to do so would require driving for maybe hundreds of miles with that misfire, but I only felt it misfire once when the light first came on. Otherwise it would just shut off, while driving. So I really doubted their diagnosis. The plugs were not very old, the O2 sensors and coil packs were covered, but not the cats. Deep in the warranty agreement it states they are not covered. I think they just wanted me to have to actually pay for something, or just ripped me off. I asked if I could get the other stuff done and maybe do the cats if the problem persisted. This was $2k I didn’t have mind you. They told me that I could do that, but anything damaged by not replacing them would not be covered under warranty. They basically “bullied” me into it, with leverage. That loose description led me to believe that they could claim just about anything after that. Oil pump dies? Shoulda gotten those cats when we told you to. That’ll be another $2000 sir. So I kept asking around and searching online and finally called the service advisor and explained my predicament. They got a tech on the phone and I asked why no standard symptoms of “bad catalytic converters”? Why did it fire right back up and drive like nothing happened for many miles if they were clogged when hot? He gave me the above explanation. I know I got ripped off. But has ANYONE, EVER heard of such a thing happening? So far even the pay-for-an-answer people online said they thought I had been duped. And I phrased to not induce an expected answer, kind of like above, but shorter. Any metal swells when heated, but enough to block exhaust flow and shut down the car? And the temp gauge never moved either. And it certainly didn’t run like tha t car would if it was really hot, like with heat soak. I bullshit. I am reaching out because I intend to take them to court, and if I can’t get one single reputable response saying that “yes, they can swell that much and he was telling the truth”, then they are screwed. And that is just the start. After tons of research, I have discovered that Chrysler has been screwing people on a criminal scale since the early 2000’s. Not like the usual, like we all know that all dealership jerk people around, and so do the manufacturers, but just within the law, usually, well this is fraud, and I can prove it. So if you have a late model Chrysler product and you have been having problems with it and the dealership seems to be giving you a story or ripping you off or even not fixing it at all, please let me know. They have been selling parts to customers by the thousands that did not fix the problem and the dealership just convinces them to spend more money and “try this”, and if that doesn’t work “try this”. All while not giving a refund on the part that didn’t fix the problem and most likely was perfectly fine anyway. My contention is that they know the problem , have been lying to America for 15+ years, and ripping people off the whole time. And I’m in kind of a semi-unique position to make these claims. Through interviews and reading comments and forums I have discovered this: if I were a regular “paying” customer with no warranty they would sell me parts all day long claiming that it will fix the problem, and when it doesn’t they make an excuse for not refunding money and the tell them that the next parts will definitely fix it. People have even replaced the transmission, only to have the problem come back a week later, because the transmission was never the problem. People have blown thousands of dollars on these cars and the problem ALWAYS PERSISTS. And that is because they just replace with the same crappy but new part that came off, which is sure to fail. So far I have discovered that the problem is with the computer infrastructure of the car, where kind of like your computer, when something goes awry, it freezes up. Well when these cars have any kind of intermittent connection, short, etc. they just shut down. They will always start right back up though, sometimes without another issue for months, sometimes minutes. So every time they replace a part, that wiring harness connector gets cleaned(if they’re doing it right) properly and reconnected, generally improving the connection, but not always, and not always for good. It’s like the old saying, if they know this, they are lying and in on the con, and if they don’t, then they aren’t qualified to be a car dealership or Chrysler a manufacturer. They will be shut down, very soon, mark my word. Maybe not by me, but they will. I give them till 2022. That’s three years. I think it would take that long for my case to be seen if it ever happens, but meanwhile I’m building up evidence, and if you feel like you’ve been screwed by ANY automobile manufacturer please share your stories. Read the Magnusson-Moss Warranty Act and you’ll see that they are trampling all over the implied warranty part. By the way, there is a You Tube Video of a sheriff’s department showing the suspension parts from one of their Chargers. It is scary. 98% of cars and trucks out there have suspension bushing that will last at least 100,000 miles, but more likely upwards of 200,000. Well the parts on all of these Chargers, 300s, and Magnums have a 20-30,000 mile average service life. That right there breaks the implied warranty rule. It is absolutely incomparable with any other comparable product on the market, and by a huge margin. Thanks for your time. Hit me back and I’ll figure out how to link you to tons of info and I’m about to open a You Tube channel devoted to these issues.

  13. so many thieves love to steal catalytic converters cuz of the platinum they contain and there worth big bucks if you sell them to a scrapper.

  14. in the past in there earlier episodes they didn't have that donut backdrop that's in front of the microwave. You could see their reflection of cars driving by

  15. Didn't know cats also cleaned exhaust smoke. Must be the same way they warm up your feet in bed when you pour boiling water down their throats. Cats are great.

  16. I guess he would bs and then scrap them.. he's destroyed more cars then he's fix..never use a unlicensed mechanic.. self taught = uninformed.

  17. So basically if you have a cat you are contributing to climate change more than someone who doesn't have one. Also the smog actually blocks sunlight. This is why we know that the amount of sunlight reaching the ground has increased (research global brightening).

  18. The catalytic converter is probably the most important device that was ever invented for the automobile industry, it is in the top 3 list for sure without a doubt.

  19. My buddy just got his stolen straight from under his car today. A prius, but that still doesnt make it right. People are literally welding on cages so people dont steal them.

  20. Somebody cut my catalytic converter out tonight at the mall smh I had no idea they were worth so much money for 30 seconds of thievery.

  21. Hi i don't know much about cars so please help? Haha

    Is the catalytic converter and DPF the same?

    I'm trying to filter car pollution using natural products for a school project (tmi my group members are the worst).

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