My understanding is that catalytic converters are no longer needed on new cars. They are obsolete. Modern fuel injection can make the combustion so clean that they are unnecessary. In fact, under some conditions cats have a negative effect on both fuel economy and emissions. Cold starts and idling in traffic on cold days especially. Cats were designed to eliminate excess hydrocarbon emissions (un-burnt fuel) in the 70's when top technology was carburetors. Carburetors are unable to be tuned to operate efficiently under all conditions. And conditions are constantly changing as you operate your car. In order to compensate for changing conditions without sacrificing performance and driveability a carburetor equipped car is always running richer ( more gas, less air) then needed for optimum efficiency. This has been true since the invention of the internal combustion engine. In the 70's the catalytic converter came along to burn the excess fuel coming out of the exhaust. The converter does not operate on a separate power source, such as electricity, it is fully powered by the un-burnt fuel it is trying to eliminate. Unfortunately it needs more fuel to operate then is available in the exhaust of an engine equipped with a modern closed loop fuel injection system. In other words the car uses more fuel then necessary just to keep the catalytic converter operating! I do not claim to be any sort of combustion engineer and there may be some advantages continuing the use of these things. I am interested in informed opinions.
My understanding of catalytic converters.
- Thread starter Chipg56
- Start date
R Bahnsen
Member
The fact is that if auto manufactures did not have to spend $ equipping autos with catalyst systems to meet emissions they would not , yes engines of today are indeed much cleaner and more efficient than ever but the catalyst also control NOX emissions witch is when the nitrogen in the air we breath is heated over 2500 degrees ( lean burn ) it truly is chemistry at work.
I did not get this from the internet, I know some of it from personal observations and some from respected friends. I understand they were mandated by government in the 70's and the mandate was never removed. Hell you can smell the rich mixture from the smelll off hydrogyn sulfide on cold days.
"J'-remy
Member
The Car companies have tons of lobbyist's and plenty of $$$$. if they could show the EPA what your ' respected friends' claim.. they would.
the auto industry would quit adding seatbelts and windshield wipers if they could. Lotus came out with the Evora because people complained they only had two seaters. the rear seat was a $3000 option
Not true, they are not obsolete, they are still used on cars today. Now there is new technology out there to store and capture carbon but not yet ready for use.
Not true it may be able to be clean during certain engine conditions, but not at all times, like idle and cruise may be very clean, but at acceleration and full loads they may actually add more fuel - it takes fuel to make power how would they get 300 horse out of a six cylinder that gets 30 mpg without adding fuel at correct times it is needed.
Not true the cat is simply there during cold starts not doing anything, it does nothing until it is warmed up. Fuel economy on cold days will be less due to the need of the fuel injection to add fuel to compensate for the denser air. Keeping the air fuel ratio near stoichiometric.
True, but they were not necessarily a standard carb, they were electronic feedback carbs, the cats were also not like the cats of today.
Many cars in the 70's were actually running lean and woke up quite nicely with a little cam timing adjustment, a little more fuel, and blocking the EGR valve the changes gave better fuel economy and power however the emission's went up. The lean conditions and cam timing were for reduced hydrocarbons (unburned fuel) the EGR valve reduced NOX
The modern fuel injection system keep the engine happy with the correct amount of fuel. The system cycles between rich and lean about every 1/2 to 1 1/2 seconds once the 02 sensor is warm (600 degrees). The rich to fire the cat then way lean with the average being near Stoichiometric or slightly less during cruise and idle. that is how we get such great mileage today on the highway.
I could go on and on with much more info but it is time for supper.
R Bahnsen
Member
Thank You !
The modern fuel injection system keep the engine happy with the correct amount of fuel. The system cycles between rich and lean about every 1/2 to 1 1/2 seconds once the 02 sensor is warm (600 degrees). The rich to fire the cat then way lean with the average being near Stoichiometric or slightly less during cruise and idle. that is how we get such great mileage today on the highway.
I could go on and on with much more info but it is time for supper.
Hope you had a good meal.....But this last point in your post goes to crux of what I was trying to say. The computer dumps more fuel in simply to keep the cat hot. If this was not needed wouldn't the overall efficiently of the system increase? Is the actual amount of fuel negligible? Lots of rotten egg smell sitting in traffic on cold days. maybe I could have gotten my question out there with a much shorter post.
I could go on and on with much more info but it is time for supper.
Hope you had a good meal.....But this last point in your post goes to crux of what I was trying to say. The computer dumps more fuel in simply to keep the cat hot. If this was not needed wouldn't the overall efficiently of the system increase? Is the actual amount of fuel negligible? Lots of rotten egg smell sitting in traffic on cold days. maybe I could have gotten my question out there with a much shorter post.
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spincycle
Member
R Bahnsen
Member
Same here, and the engine hardly ever runsMy Hybrid has one .
I'm not so sure they are needed .
If it goverment mandated they gotta be there . Also with the lobbyists they should be able to change that except tree huggers have lobbyists as well .
They may be a bigger force actually .
