# Ceramic cat vs metal cat



## wazzap1101 (May 1, 2009)

is a ceramic cat less durable than a metal cat? and with the case of AWEs dp, does this contribute to the $500 difference in DP?


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## REDsLINE (Mar 24, 2009)

bump for replies. Also, do they sound differently?


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## placenta (Jun 3, 2003)

yes, metal cats are more desirable than ceramic. and yes, they are usually more expensive. The HJS is the "famous" top line metal cat, and the expensive downpipes usually run that cat. I would not say swapping cats would change the sound in any way noticable. Cell count maybe, but probably not.


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## wazzap1101 (May 1, 2009)

would the ceramic cat melt or crack or something, and under what circumstances? BTW im running w/m 24/7, so my projected EGT will be lower than normal


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## placenta (Jun 3, 2003)

*Re: (wazzap1101)*


_Quote, originally posted by *wazzap1101* »_would the ceramic cat melt or crack or something, and under what circumstances? BTW im running w/m 24/7, so my projected EGT will be lower than normal

theyre not crap dood.. just not as long lasting as metal cats which probably last forever. for some reason Magnaflow ceramic cats have a bad rap, so ill be finding out for myself since I installed one tonight. I dont expect any problems for at least 2 years hopefully.


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## wazzap1101 (May 1, 2009)

*Re: (placenta)*


_Quote, originally posted by *placenta* »_
theyre not crap dood.. just not as long lasting as metal cats which probably last forever. for some reason Magnaflow ceramic cats have a bad rap, so ill be finding out for myself since I installed one tonight. I dont expect any problems for at least 2 years hopefully.

I know they cant be crap, I just wanna weight my options a little bit. The price difference between the metal nd ceramic is whats confusing me. You can buy 2 ceramic catted DPs for the price of one metal DP. Id like to grab an AWE dp at waterfest, but I wanna figure out the + and - of each before I make a purchase. http://****************.com/smile/emthup.gif


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## 2kjettaguy (Dec 24, 2000)

*Re: (wazzap1101)*

The price difference in any catalytic converter is based on the loading, not the base material of the honeycomb. A catalytic converter is basically a long screen made of either ceramic or a metal foil. This screen is dipped and coated in a bath of liquid metal. The recipe for this bath is made up of precious metals like platinum, gold, and rhodium. These metals are the catalyst which alters the state of the gases passing through. The more expensive the cat, the more precious metals in the bath, the better it converts the gases, the less your chances for a CEL. 
When you're looking at a replacement cat, the main question people always ask is "what's a good performance cat?". Catalytic converter performance is double sided. There's performance in terms of air flow and performance in terms of emissions conversion. Which one do you want? 
*Cell Count*
Stock is 400 cells per square inch. Alot of aftermarket cats are 200. I've seen 100 and 150 in the higher end. The higher the cell count, the lower the flow. The lower the cell count, the better the flow. Higher will convert more gases, lower will let them pass right by. 
*Catalyst Material*
Ceramic has long been used the build the catalyst. It holds up to long heat cycles, but doesn't handle vibration well. Ceramic catalysts are always padded by a layer of heat resistant padding between the shell and the honeycomb. Metal catalysts use a thin metal foil which creates the honeycomb. Sometimes this foil catalyst is dipped in a bath which is based on a liquid ceramic, making it look like a ceramic catalyst. Ceramic catalysts are known to fail by blowing apart. This would only happen if the padding failed, causing the honeycomb to rattle loose and break apart. I've been using ceramic cores in our systems for over 5 years and have never had one break apart. We use metal now, but because of the outer construction. 
*Catalyst Recipe*
This is hard to get detailed information. You can tell what's in a cat almost instantly by price. Precious metals cost everyone the same. The more expensive the cat, the more precious metals. There's no cheap cat loaded with platinum. The better the recipe, the more gases that are converted, and the chances of a CEL decrease. 
*Construction*
To my knowledge you can't buy a cat made of aluminized steel these days. It's 409 stainless or 304. 304 is the shiny stuff, loaded with more chromium for better corosion resistance. 409 is mild steel with just enough chromium to slow down oxidation. Watch for companies selling "full 304" stainless steel systems with 409 cats. There's nothing wrong with 409, but it's not worth the price of 304 and won't "last a lifetime" as advertised. False advertising annoys me if you can't tell. Anything Magnaflow is 409. 
*Price*
Price is based on all of the above. The biggest cost is the precious metals. Metal honeycombs cost more, as do spun 1-piece bodies. Multi-piece welded bodies tend to leak at the welds, as they are mass-produced by robots that don't have eyeballs. 304 stainless costs more. 
It's hard to have your cake and eat it too, without paying for it. The stock cat is the best for converting the gases, hence no CEL. An aftermarket cat with little precious metals will cause a CEL. The lower the cell count the better the chances. If you're looking for performance on a budget, get ready to battle a CEL. If you're looking for performance with an unlimited budget, it's there. You just have to find it. If you're looking to eliminate the chances of a CEL, buy a used stock downpipe and cut the ends off the second cat at 3".


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## wazzap1101 (May 1, 2009)

*Re: (2kjettaguy)*


_Quote, originally posted by *2kjettaguy* »_The price difference in any catalytic converter is based on the loading, not the base material of the honeycomb. A catalytic converter is basically a long screen made of either ceramic or a metal foil. This screen is dipped and coated in a bath of liquid metal. The recipe for this bath is made up of precious metals like platinum, gold, and rhodium. These metals are the catalyst which alters the state of the gases passing through. The more expensive the cat, the more precious metals in the bath, the better it converts the gases, the less your chances for a CEL. 
When you're looking at a replacement cat, the main question people always ask is "what's a good performance cat?". Catalytic converter performance is double sided. There's performance in terms of air flow and performance in terms of emissions conversion. Which one do you want? 
*Cell Count*
Stock is 400 cells per square inch. Alot of aftermarket cats are 200. I've seen 100 and 150 in the higher end. The higher the cell count, the lower the flow. The lower the cell count, the better the flow. Higher will convert more gases, lower will let them pass right by. 
*Catalyst Material*
Ceramic has long been used the build the catalyst. It holds up to long heat cycles, but doesn't handle vibration well. Ceramic catalysts are always padded by a layer of heat resistant padding between the shell and the honeycomb. Metal catalysts use a thin metal foil which creates the honeycomb. Sometimes this foil catalyst is dipped in a bath which is based on a liquid ceramic, making it look like a ceramic catalyst. Ceramic catalysts are known to fail by blowing apart. This would only happen if the padding failed, causing the honeycomb to rattle loose and break apart. I've been using ceramic cores in our systems for over 5 years and have never had one break apart. We use metal now, but because of the outer construction. 
*Catalyst Recipe*
This is hard to get detailed information. You can tell what's in a cat almost instantly by price. Precious metals cost everyone the same. The more expensive the cat, the more precious metals. There's no cheap cat loaded with platinum. The better the recipe, the more gases that are converted, and the chances of a CEL decrease. 
*Construction*
To my knowledge you can't buy a cat made of aluminized steel these days. It's 409 stainless or 304. 304 is the shiny stuff, loaded with more chromium for better corosion resistance. 409 is mild steel with just enough chromium to slow down oxidation. Watch for companies selling "full 304" stainless steel systems with 409 cats. There's nothing wrong with 409, but it's not worth the price of 304 and won't "last a lifetime" as advertised. False advertising annoys me if you can't tell. Anything Magnaflow is 409. 
*Price*
Price is based on all of the above. The biggest cost is the precious metals. Metal honeycombs cost more, as do spun 1-piece bodies. Multi-piece welded bodies tend to leak at the welds, as they are mass-produced by robots that don't have eyeballs. 304 stainless costs more. 
It's hard to have your cake and eat it too, without paying for it. The stock cat is the best for converting the gases, hence no CEL. An aftermarket cat with little precious metals will cause a CEL. The lower the cell count the better the chances. If you're looking for performance on a budget, get ready to battle a CEL. If you're looking for performance with an unlimited budget, it's there. You just have to find it. If you're looking to eliminate the chances of a CEL, buy a used stock downpipe and cut the ends off the second cat at 3". 

wow, I couldn't have asked for better info. Thanks 2kjettaguy for making things clearer. http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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## placenta (Jun 3, 2003)

*Re: (2kjettaguy)*


_Quote, originally posted by *2kjettaguy* »_The price difference in any catalytic converter is based on the loading, not the base material of the honeycomb. A catalytic converter is basically a long screen made of either ceramic or a metal foil. This screen is dipped and coated in a bath of liquid metal. The recipe for this bath is made up of precious metals like platinum, gold, and rhodium. These metals are the catalyst which alters the state of the gases passing through. The more expensive the cat, the more precious metals in the bath, the better it converts the gases, the less your chances for a CEL. 
When you're looking at a replacement cat, the main question people always ask is "what's a good performance cat?". Catalytic converter performance is double sided. There's performance in terms of air flow and performance in terms of emissions conversion. Which one do you want? 
*Cell Count*
Stock is 400 cells per square inch. Alot of aftermarket cats are 200. I've seen 100 and 150 in the higher end. The higher the cell count, the lower the flow. The lower the cell count, the better the flow. Higher will convert more gases, lower will let them pass right by. 
*Catalyst Material*
Ceramic has long been used the build the catalyst. It holds up to long heat cycles, but doesn't handle vibration well. Ceramic catalysts are always padded by a layer of heat resistant padding between the shell and the honeycomb. Metal catalysts use a thin metal foil which creates the honeycomb. Sometimes this foil catalyst is dipped in a bath which is based on a liquid ceramic, making it look like a ceramic catalyst. Ceramic catalysts are known to fail by blowing apart. This would only happen if the padding failed, causing the honeycomb to rattle loose and break apart. I've been using ceramic cores in our systems for over 5 years and have never had one break apart. We use metal now, but because of the outer construction. 
*Catalyst Recipe*
This is hard to get detailed information. You can tell what's in a cat almost instantly by price. Precious metals cost everyone the same. The more expensive the cat, the more precious metals. There's no cheap cat loaded with platinum. The better the recipe, the more gases that are converted, and the chances of a CEL decrease. 
*Construction*
To my knowledge you can't buy a cat made of aluminized steel these days. It's 409 stainless or 304. 304 is the shiny stuff, loaded with more chromium for better corosion resistance. 409 is mild steel with just enough chromium to slow down oxidation. Watch for companies selling "full 304" stainless steel systems with 409 cats. There's nothing wrong with 409, but it's not worth the price of 304 and won't "last a lifetime" as advertised. False advertising annoys me if you can't tell. Anything Magnaflow is 409. 
*Price*
Price is based on all of the above. The biggest cost is the precious metals. Metal honeycombs cost more, as do spun 1-piece bodies. Multi-piece welded bodies tend to leak at the welds, as they are mass-produced by robots that don't have eyeballs. 304 stainless costs more. 
It's hard to have your cake and eat it too, without paying for it. The stock cat is the best for converting the gases, hence no CEL. An aftermarket cat with little precious metals will cause a CEL. The lower the cell count the better the chances. If you're looking for performance on a budget, get ready to battle a CEL. If you're looking for performance with an unlimited budget, it's there. You just have to find it. If you're looking to eliminate the chances of a CEL, buy a used stock downpipe and cut the ends off the second cat at 3". 

nice little post!


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## JLT (May 18, 2008)

i have had a number of different set ups on my last 3 cars, and i found that ceramic HFC's are not necessarily a bad thing.


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## [email protected] (Sep 30, 1999)

Nice summary. 
Just a few corrections:


_Quote, originally posted by *2kjettaguy* »_
*Cell Count*
Stock is 400 cells per square inch. 


The stock FSI cats are ~600 cells per square inch. Both the primary (warm-up) and secondary (main) cats. 

















The primary cat sits right at the turbo outlet to get up to temperature fast and minimize cold running emissions. A cat only begins to work when it is hot, so can thickness can play a part in how much heat is retained in the core. 
The TSI primary cat is ~800 cells per square inch, by the way.

_Quote, originally posted by *2kjettaguy* »_
*Catalyst Material*
Ceramic has long been used the build the catalyst. It holds up to long heat cycles, but doesn't handle vibration well. Ceramic catalysts are always padded by a layer of heat resistant padding between the shell and the honeycomb. Metal catalysts use a thin metal foil which creates the honeycomb. Sometimes this foil catalyst is dipped in a bath which is based on a liquid ceramic, making it look like a ceramic catalyst. Ceramic catalysts are known to fail by blowing apart. This would only happen if the padding failed, causing the honeycomb to rattle loose and break apart. I've been using ceramic cores in our systems for over 5 years and have never had one break apart. We use metal now, but because of the outer construction.

I agree, and in a non-close coupled environment like in the Mk5, ceramic can withstand the exhaust pulse beating. However, placing a typical aftermarket ceramic cat right at the outlet of the turbo (close coupled) will hammer it apart rather quickly. So placement of cat plays a role in core material choice.


_Quote, originally posted by *2kjettaguy* »_
*Price*
Price is based on all of the above. The biggest cost is the precious metals. Metal honeycombs cost more, as do spun 1-piece bodies. Multi-piece welded bodies tend to leak at the welds, as they are mass-produced by robots that don't have eyeballs. 304 stainless costs more. 

Another large price factor is the actual construction method of the core. Low cost, commonly used domestic metal cats that run around $80-100 each not only have a bare minimum of precious metal coating, but they are also a wound construction.
Corrugated metal sheets are "wound" into a cylinder, and stuffed in a can. Such a simple construction methods typically result in "telescoping" of the core center over time, which ultimately destroys the cat:








Between this structural failure and the frequency of CELs on late model cars are the exact reasons we moved away from the cheapie cats and have been using German made HJS cats exclusively for last few years.
As you can see at the red arrows in the photo below, the HJS core is a tri-lobe design which adds greatly to its strength. Further, the metal sheet is wound and then brazed together to ensure integrity under the harshest pounding. It simply will not "telescope".









Here is a picture of a cheapie domestic metal cat. You can see that there are no special winding methods used to ensure strength:


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## wazzap1101 (May 1, 2009)

*Re: ([email protected])*


_Quote, originally posted by *[email protected]* »_Nice summary. 
Just a few corrections:
The stock FSI cats are ~600 cells per square inch. Both the primary (warm-up) and secondary (main) cats. 

















The primary cat sits right at the turbo outlet to get up to temperature fast and minimize cold running emissions. A cat only begins to work when it is hot, so can thickness can play a part in how much heat is retained in the core. 
The TSI primary cat is ~800 cells per square inch, by the way.
I agree, and in a non-close coupled environment like in the Mk5, ceramic can withstand the exhaust pulse beating. However, placing a typical aftermarket ceramic cat right at the outlet of the turbo (close coupled) will hammer it apart rather quickly. So placement of cat plays a role in core material choice.

Another large price factor is the actual construction method of the core. Low cost, commonly used domestic metal cats that run around $80-100 each not only have a bare minimum of precious metal coating, but they are also a wound construction.
Corrugated metal sheets are "wound" into a cylinder, and stuffed in a can. Such a simple construction methods typically result in "telescoping" of the core center over time, which ultimately destroys the cat:








Between this structural failure and the frequency of CELs on late model cars are the exact reasons we moved away from the cheapie cats and have been using German made HJS cats exclusively for last few years.
As you can see at the red arrows in the photo below, the HJS core is a tri-lobe design which adds greatly to its strength. Further, the metal sheet is wound and then brazed together to ensure integrity under the harshest pounding. It simply will not "telescope".









Here is a picture of a cheapie domestic metal cat. You can see that there are no special winding methods used to ensure strength:










http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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## 2kjettaguy (Dec 24, 2000)

*Re: (wazzap1101)*

Todd - excellent post, corrections apreciated. I wasn't aware of the true factory cell counts. I've also never seen that type of winding in an aftermarket cat.


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## KingUnderpants (Sep 8, 2004)

*Re: ([email protected])*

This looks a lot like the 200 cell metallic Magnaflow cat that I have on my downpipe. Are they lower quality? I thought they had a decent reputation... anyone had bad experiences with them?


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## [email protected] (Sep 30, 1999)

*Re: (davidraeside)*


_Quote, originally posted by *davidraeside* »_This looks a lot like the 200 cell metallic Magnaflow cat that I have on my downpipe. Are they lower quality? I thought they had a decent reputation... anyone had bad experiences with them?


Magnaflow is not an actual cat manufacturer. They are having their cats made by a subcontractor. So are almost all the other "name brand" cat sellers out there.
There are basically two main US sources for domestic cats and they both build at about the same quality level. That is why they only cost ~$80-100 ea, where the HJS units are about four times that cost.
Actually, even HJS buys their product from another source. Emitec makes the internal cores for HJS and HJS puts them in a can. Emitec is the OE supplier to about all the German car manufacturers.


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## blackvento36 (Mar 17, 2003)

*Re: (2kjettaguy)*

I agree with most of what you said, other than this
_Quote, originally posted by *2kjettaguy* »_ .........Anything Magnaflow is 409. 


I've been running a Magnaflow/Carsound ceramic cat on a downpipe I built over 2 years ago. I used 304 tubing and the cat has about the same rust on it as the tubing does, so I'd have to say the cat is 304. I have an Autotech cat-back that's supposedly made by Magaflow, and that is 409, and has rusted more than the downpipe/cat. 
Either way, it doesn't matter much, 409 stainless just winds up not being as pretty as 304. 409 rusts on the surface and that protects the steel underneath. 409 will still likely outlast your car. The Magnaflow cat hasn't given me a single problem in 2 years. I pass emissions and my car doesn't smell like sulphur. 
I can't say how it performs against more expensive metallic cats, but I did dyno the car on a 90* day and made 232hp/262ft-lb at the wheels with only this 3" exhaust, an intake and an EIP flash (haha....it was cheap)


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## KingUnderpants (Sep 8, 2004)

*Re: (blackvento36)*


_Quote, originally posted by *blackvento36* »_I agree with most of what you said, other than this
I've been running a Magnaflow/Carsound ceramic cat on a downpipe I built over 2 years ago. I used 304 tubing and the cat has about the same rust on it as the tubing does, so I'd have to say the cat is 304. I have an Autotech cat-back that's supposedly made by Magaflow, and that is 409, and has rusted more than the downpipe/cat. 
Either way, it doesn't matter much, 409 stainless just winds up not being as pretty as 304. 409 rusts on the surface and that protects the steel underneath. 409 will still likely outlast your car. The Magnaflow cat hasn't given me a single problem in 2 years. I pass emissions and my car doesn't smell like sulphur. 

Thats somewhat comforting, I'd hate to think that my cat is a ticking timebomb... which it might actually be in reality. Good to know that you pass emissions too, I'm kinda worried about that.


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