Cermaic vs Metal Core CAT for Gen1 Emissions

[TexasPettey]

Does anyone have experience or data regarding using high flow CATs with Ceramic vs Metal cores? I did some research online that indicated that ceramic cores would do better are removing CO and HC emissions at lower speed and idle with an OBD-1 computer. It seemed to be because of the single O2 sensor (no sensor behind the CAT). That also indicated that metal cores would have better flow and handle higher total flow before failure.

Any experience here? I've got a problem passing low speed emissions on my Gen1 with metal core ROE CATS. I'm thinking about trying a move to ceramic to help that out.

 

[Slithr]

Call JonB, I'm sure he could answer your Hi-Flo Cat questions ... he has answered mine

360 837 3937
or www.partsrack.com

 

[plumcrazy]

i agree, jonB seems to be the cat expert around here.

 

[Camfab]

Put the stock cats back in and do your testing. If you don't have them, there is a current thread where someone is trying to sell a pair.

 

[JonB]

i agree, jonB seems to be the cat expert around here.

Long Answer:

The terms "ceramic" and "metallic" refer to the substrate of a
converter, and substrate material has almost nothing to do with the
efficiency of a converter. The process that "cleans" exhaust gases
(converts HC, CO and NOx to carbon dioxide and water) occurs because of
the precious metals (platinum, palladium, rhodium) and other compounds
contained in the coating that's applied to a substrate. If you coat a
metallic and a ceramic substrate with the same formulation, there should
be little if any difference in the efficiency with which the converter
operates-- assuming the number of cells and substrate length are the
same.

One potential performance difference is the effect of air flow
rate. Metallic converters have thinner walls than ceramics, so all
things being equal, a metallic will offer higher flow rates. That being
the case, exhaust gases will pass through a metallic substrate faster,
so the potential does exist for less efficient conversion than would be
experienced with a ceramic converter. However, at low engine speeds,
exhaust flow volume and velocity is so low, the flow capacity of a
converter has virtually no effect. The advantage of a metallic substrate
is at high engine speeds where flow capacity does make a difference with
respect to power output.

Keep in mind that you can't lump all ceramic converters or all metallic
converters together any more than you can lump all Vipers together.
Obviously, a Viper with a supercharged engine will have different
performance characteristics than one with a naturally aspirated engine.
Similarly, the chemistry (amount of precious metals) of converter
coatings makes a significant difference in their performance. Many of
the cheaper converters as made in China have the absolute minimum amount of precious
metals, so they're marginally effective for a relatively short period of
time. Please: Know who makes your converter, and where!

As for the rear oxygen sensor, it has no EFFECT on converter operation
or engine operation for that matter. Its only function is to monitor
converter operation.

 

[TexasPettey]

Thanks for the information, Jon, and for the extended details over the phone. It's nice to talk with a vendor that knows the product. I called a number of places that could only quote info that was already on the web site. They were completely useless.

I ended up with RandomTech's from Jon. I'll report back on how it helps with the emissions testing.

Long Answer:

The terms "ceramic" and "metallic" refer to the substrate of a
converter, and substrate material has almost nothing to do with the
efficiency of a converter. The process that "cleans" exhaust gases
(converts HC, CO and NOx to carbon dioxide and water) occurs because of
the precious metals (platinum, palladium, rhodium) and other compounds
contained in the coating that's applied to a substrate. If you coat a
metallic and a ceramic substrate with the same formulation, there should
be little if any difference in the efficiency with which the converter
operates-- assuming the number of cells and substrate length are the
same.

One potential performance difference is the effect of air flow
rate. Metallic converters have thinner walls than ceramics, so all
things being equal, a metallic will offer higher flow rates. That being
the case, exhaust gases will pass through a metallic substrate faster,
so the potential does exist for less efficient conversion than would be
experienced with a ceramic converter. However, at low engine speeds,
exhaust flow volume and velocity is so low, the flow capacity of a
converter has virtually no effect. The advantage of a metallic substrate
is at high engine speeds where flow capacity does make a difference with
respect to power output.

Keep in mind that you can't lump all ceramic converters or all metallic
converters together any more than you can lump all Vipers together.
Obviously, a Viper with a supercharged engine will have different
performance characteristics than one with a naturally aspirated engine.
Similarly, the chemistry (amount of precious metals) of converter
coatings makes a significant difference in their performance. Many of
the cheaper converters as made in China have the absolute minimum amount of precious
metals, so they're marginally effective for a relatively short period of
time. Please: Know who makes your converter, and where!

As for the rear oxygen sensor, it has no EFFECT on converter operation
or engine operation for that matter. Its only function is to monitor
converter operation.

 

[JonB]

Thanks T.P.

But in total fairness to the other brand of failed cats you have on your car, I now know they are SIX YEARS OLD.....and served a good, useful life.
Six+ years ago was probably a different item/better product altogether.....cheaper Chinese stuff was not widespread then.

 

[TexasPettey]

Thanks T.P.

But in total fairness to the other brand of failed cats you have on your car, I now know they are SIX YEARS OLD.....and served a good, useful life.
Six+ years ago was probably a different item/better product altogether.....cheaper Chinese stuff was not widespread then.

I wasn't bashing the cats I have on so much as some of the other vendors/manufacturers. As an example, I talked to a Magnaflow 'technical' rep who told me that their largest CAT was for a 6L motor and they couldn't sell me 2, one for each side. I then asked what size their CAT core for the C6 7L motor was, and he was not sure why they had a solution for that car. Lots of other interesting conversations with so called 'technical' sales reps.

 

[got one]

Great info Jon...you hooked me up with my exhaust system back in the day and several years later it is still running strong. I too went with the RT cats.

 

[Camfab]

Sounds like you got some great advice from John, but if you still have issues passing your test, nothing will do as good of a job as the factory converters. John may have a good used set to have on hand for the future. Emissions testing is actually getting more stringent for all older cars in CA, it's only a matter of time when your state follows suit.