I have been doing some research on catalytic converters and I also want to learn more from everyone that is knowledgable on the subject. What I have found so far:

1. There are two types of carrier/honeycomb/matrix available; ceramic and metallic. Metallic cats are the newer technology with many benefits including:
- Shorter light off time
- Less risk of overheating
- Less back pressure
- Larger effective area
- Greater catalytic capacity
- Smaller and more flexible design
- Thinner walls
- Higher mechanical strength
- Better resistance to thermal shock
Unfortunately the metallic carrier is much more expensive than the established ceramic technology.

3. Placement of the catalytic converter is important as you want it to get up to temperature quickly and maintain the temperature between 700-1000deg.F. If the converter is too cold, it will not do its job properly and if it is too hot, the converter will break down over time. If a mixture is too rich and fuel is being introduced into the exhaust, this fuel will burn in the catalytic converter resulting in temperatures over 2000deg.F which causes significant damage. Rich mixtures are much more damaging than lean mixtures (to the converter that is... a different story for your engine)

2. There are different emission standards that catalytic converters need to comply to:
European standards over the years (g/km)
Tier.........Date...........CO.......HC.........HC +NOx......NOx........PM
Euro 1......1992.........3.16.......-............1.13...........-...........-
Euro 2......1996..........2.2........-.............0.5...........-...........-
Euro 3......2000.........2.30.....0.20............-...........0.15.........-
Euro 4......2005..........1.0......0.10............-...........0.08........-
Euro 5....mid-2008.......1.0.....0.075...........-...........0.06........-

USA Standards (g/mile)
.................Date.........CO........HC........ NMHC.......NOx.......PM
EPA Tier 1..................3.4........0.41.......0.25..... ...0.4.......0.08
EPA Tier 2....2008+.....0.100......3.4.........0.14........-.........0.015

California standards (g/mile)
.........................NMOG.......CO.........NOx ........PM.......HCHO
Tier 1..................0.25.........3.4.........0.4... ....0.08.........-
LEV11.................0.075........3.4.........0.0 5........-........0.015
NMOG - non-methane organic gases
HCHO - formaldehyde

3. The carrier has different CPIS (cells per square inch) and is typically available with counts 100, 200, 300 or 400. Increasing the CPIS increases the surface area of the catalyst but also increases the pressure drop /length. To meet the emission standards however, a lower CPIS carrier will need to have a longer length (for same diameter casing), therby increasing the pressure drop anyway. From what I can tell, it is better to have a higher CPIS and a shorter length carrier. Alternatively a larger carrier diameter can help. Eg. I have seen one high-flow cat manufacturer has a carrier: CPIS=400 and 4"dia x 3"length for 2.5-3.5L motors (two cats for a 5-7L motor). I dont know what the aftermarket C5 & C6 exhaust systems (from various LSX exhaust suppliers) use.

4. In addition to CPIS and total carrier volume, the catalytic coating (palladium, platinum elements and rhodium) concentration can be altered by the manufacturer. These elements are VERY expensive and by applying a thinner coating, significant cost savings can be made. I think that some of the low cost LSX exhaust manufacturers might look at this first if they are trying to cut costs and lower their selling prices. Unfortunately, the thinner the coating, the less catalytic conversion and less likely that the converter will meet the emission standards (or last a long time).

So now we can see that not all catalytic converters are created equal. My guess is that the cheaper catalytic converters out there are built with lower cost carriers, lower carrier volumes, lower CPIS or lower catalytic concentration coating. All these factors will result in a catalytic converter that does not do the job properly or if it does do the job properly, will have a higher pressure drop than a more expensive catalytic converter.

As the saying goes (and this is especially true for cats), you get what you pay for. When in doubt, ask the manufacturer about the above. I'm done

 

Just bought two Magnaflow Metallic Spun converters for my car. Flow is supposed to be over 580cfm per converter. That will support well over 500hp without restriction.

 

So what's a good number to have on the catalytic coating side of the story?

 

Thats why I bought a Dynamaxx Headers and catted Y system.They have already done the testing to see where they need to go.

 

catalytic converters have no place on a performance vehicle,
just as they have no place on an aircraft.

 

Where did you get the CFM numbers for the Magnaflows?

 

Fixed it for ya

 

Manaflow has published them. Also the numbers have been posted on this site.

 

Where?

 

Excellent job on the research C5blkvette. I did quite a bit of research a few years back and everything you listed is pretty much what I found. I got into the whole deal because I was having trouble passing an emissions test. I tried a few different types of converters with no luck, then I got a pair of Rantom Tech converters with metallic core. These not only got me past the emissions test, but the car also ran a whole lot better than with any of the others. What I found is that every manufacturer claims their converters are high flow, but some don't flow any better than stock converters and aren't as good at cleaning up the exhaust. You're right on about getting what you pay for. I was told that the actual cores, I think they call them substrates, don't affect price as much (unless you're comparing metallic with ceramic) as the coatings. That's what contains the chemicals that cause the reaction that cleans up the exhaust. You can't tell anything about the coating by looking at it, but like you said, the stuff that goes into the coating is very expensive. The better converters have more of it, which is why they're more expensive. The guys I spoke to said that the thickness of the coatings doesn't vary very much, but the amount of the expensive chemicals in the coatings does. I guess it's a little bit like motor oil. The really good stuff has a lot of additives in it and the cheap stuff is just oil, but it all looks the same. The other thing I found is that you have to be real careful about who you buy from. A friend of mine bout a pair of converters that were supposed to be one brand, and they turned out to be another (lower quality) brand. Hope this helps.

 

Check out this thread. Especially posts by Oxidizr. Has the information you are looking for. https://ls1tech.com/forums/showthrea...flow+converter

 

Thank you.

 

No problem, just thought it would help you everyone understand those little things that are stuck in the exhaust pipe. Hopefully it will help if you are legitimatly trying to pass an emissions test.

 

Rich doesn't burn up the cat, it cools it down. Rich (.8-.93 lambda) is used to cool the cats (and cool EGT). MISFIRE (of any kind - rich/lean/ignition) burns the cats VERY quickly - it requires both fuel AND O2 to burn, even in a cat (cats just finish the job of combustion, they can't swallow emissions). Even prolonged high load and RPM stoichiometric operation can burn out a cat (if the engine is large and the cats are close).

More tidbits I've learned from work -
Good substrates with cerium can store a lot of oxygen. Downstream O2 sensors are used to check the condition of the cat by checking the Oxygen Storage Capacity (OSC), usually by a lean period followed by a rich period to see how long the down O2 reads lean after the rich period is started. A good cat can hold enough O2 to read lean for 3-10 seconds. A bad cat (fails OBD) will be about less than 1 second.
Cats help produce formaldehyde - which is a big reason for low sulphur fuels.
Many cats only contain either palladium or platinum, from what I've seen, not both.
Hottest points in a cat are about 30mm in from the front face, in the center of the cat. That's typically where you'll see cats start to fail, and where I measure for catalyst hazard.
There's a heat swelling mat that insulates the brick from vibration.
Ignition retard is typically used to heat the cat during cold starts (along with lean to reduce HC and CO).
A new cat may not provide as good conversion as a cat with 1k miles or so. OEMs know this, and used prepared cats for their calibration. They also have to use aged cats in order to try to meet the endurance limits of OBD2/EURO3/4.

 

Anybody have good information on the use of a cat upstream of a turbo in a gasoline engine, as is becoming more commonplace in diesels?