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Old 07-07-2013, 02:58 PM   #1 (permalink)
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Aftermarket CATs (what's good, what's not)?

Are there CAT converters that are better than others? Here is a seller that claims the increased amount of "Rhodium" in their units is especially good for high mileage vehicles: Eastern 40799 Catalytic Converter | Auto Parts Warehouse

What do you think?

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Old 07-09-2013, 08:38 PM   #2 (permalink)
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Is this for your car or just in general?

CAT's exist to filter the exhaust gases. They don't really enhance performance in terms of power or fuel economy. In fact, once they become clogged and dirty they can actually hinder your fuel economy. The important thing is to have a clean and non-leaking CAT.

What the seller is referring to when they mention double the Rhodium is how this CAT can somehow hide your engines poor health. OBDII cars 1996 and newer usually have 2 oxygen sensors. One in front, and one behind the CAT. The goal of the 2nd sensor is to monitor the performance of the CAT, making sure it is filtering out the exhaust gases sufficiently. This seller implies that by purchasing this CAT it can cure your engines poor health that has been setting the check engine lights off.

But, any new CAT will probably be sufficient. When you get a CEL for a faulty CAT it is usually because it is clogged or has broken up inside and developed a leak that doesn't allow proper filtration. I don't believe you should pick a CAT because the seller claims it has more Rhodium.

$212 is a bit steep. Go search for Magnaflow Hi Flow CAT's on Google. You can find replacement, hi performance CAT's for about $70. I have used them twice on 2 different cars and have not had a problem. I even use one on my civic HX, which is suppose to produce even more harmful gases during lean-burn. The CAT has never triggered a CEL so I would say it can handle any high-mileage or lean-burn engine.

If you need advice on a replacement CAT for your specific car let me know. I use to have the same exhaust manifold design as you which has the built in CAT. Unless you buy a direct replacement which is expensive you have to convert your exhaust system to the 96-00 Civic EX with the standard exhaust manifold and downtube setup. I did this to my car and was able to purchase a used exhaust manifold, downtube, and brand new Magnaflow CAT for less than half the price of the replacement.
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Old 07-10-2013, 11:22 AM   #3 (permalink)
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Quote:
Originally Posted by cbaber View Post
Is this for your car or just in general?

CAT's exist to filter the exhaust gases. They don't really enhance performance in terms of power or fuel economy. In fact, once they become clogged and dirty they can actually hinder your fuel economy. The important thing is to have a clean and non-leaking CAT.

What the seller is referring to when they mention double the Rhodium is how this CAT can somehow hide your engines poor health. OBDII cars 1996 and newer usually have 2 oxygen sensors. One in front, and one behind the CAT. The goal of the 2nd sensor is to monitor the performance of the CAT, making sure it is filtering out the exhaust gases sufficiently. This seller implies that by purchasing this CAT it can cure your engines poor health that has been setting the check engine lights off.

But, any new CAT will probably be sufficient. When you get a CEL for a faulty CAT it is usually because it is clogged or has broken up inside and developed a leak that doesn't allow proper filtration. I don't believe you should pick a CAT because the seller claims it has more Rhodium.

$212 is a bit steep. Go search for Magnaflow Hi Flow CAT's on Google. You can find replacement, hi performance CAT's for about $70. I have used them twice on 2 different cars and have not had a problem. I even use one on my civic HX, which is suppose to produce even more harmful gases during lean-burn. The CAT has never triggered a CEL so I would say it can handle any high-mileage or lean-burn engine.

If you need advice on a replacement CAT for your specific car let me know. I use to have the same exhaust manifold design as you which has the built in CAT. Unless you buy a direct replacement which is expensive you have to convert your exhaust system to the 96-00 Civic EX with the standard exhaust manifold and downtube setup. I did this to my car and was able to purchase a used exhaust manifold, downtube, and brand new Magnaflow CAT for less than half the price of the replacement.
Thanks for this. Unfortunately I don't think I can swap the emissions equipment in California without the approval of the CARB authority that regulates that out here. In my last emissions test, my emissions were high but still within the required ranges ranges. The tech noted unburnt fuel in the CAT and suspected the O2 sensor. Shortly after the test I got an upstream O2 CEL. I replaced both. Do you think the unburnt fuel situation could "cure itself"? I have seen guys online "cleaning" CATs. I am not inclined to try that without clear evidence of effectiveness.
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Old 07-10-2013, 05:49 PM   #4 (permalink)
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It is very plausible that the upstream o2 sensor was causing the car to run rich, which is where the un burnt fuel comes from. Replacing the o2 sensor is part of that equation but your timing is another. If both are good then you don't have anything to worry about.

I have never heard of cleaning a CAT. Once clogged up and unable to filter the air you should scrap them. They bring tons of money. Anywhere from $50-$150 depending on size and weight. However, since your states emissions standards are more strict I'm not sure how you go about replacing a CAT. If you can do it legally then a direct replacement would be the way to go to avoid modifying the exhaust system. I doubt the CARB guys would want you switching your manifold and CAT placement, as you said. But, sounds like it passed last time so there is no reason to replace it until it fails.
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Old 07-12-2013, 09:03 PM   #5 (permalink)
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Cats can be cleaned with citric acid. See here http://bit.ly/13atVTX

For what it's worth, those reasonably priced magnaflow cats are high flow, aka about 1/2 the element inside of a normal cat. I was into the SVT mustang scene for about 6 years, some guys occasionally would throw a code with the high flow cats on there x/y pipes.

Edit: Wow, there is actually a thread a few down called "cleaning the cat" that is about using citric acid.
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Old 07-12-2013, 09:26 PM   #6 (permalink)
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Amazing info about the citric acid bath. Thanks. This Subaru Forester forum thread had some especially useful discussion, I thought: (All Years) Catalytic Converter Citric Acid Bath P0420 - Subaru Forester Owners Forum

I'll put this on my maintenance list for research early next summer, before my August smog test.
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Old 07-12-2013, 11:11 PM   #7 (permalink)
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California has a much more strict requirement for emissions.

This is reflected in the aftermarket catalytic converter costs. There is often times very little difference in actual construction and performance between parts other than one has been tested to meet CARB and AQMD requirements depending on year and model.

Some applications do have a heavier loading of Platinum, Palladium and Rhodium. Also, Cerium area might be greater. But even if a particular CAT has all of these and has not passed the California tests, it will not be considered "legal" as a replacement.

Most shops I have been to do not check the CAT that closely when I go in for testing. They simply hook the car up and run the test. More than likely, you could get away with installing a good 49 state CAT just as long as it ran clean. Just understand it will not stand up to close scrutiny and may be questioned.

As to cleaning the CAT, there is a plethora of information out there. Some of it is horribly wrong. I am familiar with cleaning cats and have performed the procedure on several applications the latest of which was my Wife's 2007 Dodge. There is a paper done as a graduate thesis from Cyprus university that is the basis for most of the YouTube experts. However, a much more concise doctoral thesis from Sweden extends the work and includes re-aggregation via chlorine reactions. The Pdf can be found here:

http://kth.diva-portal.org/smash/get...070/FULLTEXT01

Other than the re-aggregation, both papers concluded that a weak (0.1 M) concentration of heated aqueous solutions of Oxalic and Nitric acids at 50 deg C and applied in series over an 8 hour period removed over 80% of the plating phosphorus and sulfur plus other metal salts such as tin. The light off and conversion rates could be brought back to effective levels again.

My Wife's Dodge threw a code that showed the CAT had gone out. A visual check showed the upstream O2 sensor had been cross threaded by the service tech at the dealer during an unrelated repair. Since the vehicle was out of dealer warranty but still under emissions warranty (100K miles limit) a spitting match ensued between the three parties ( Dodge, the dealer and me). The legal costs would have exceeded the actual repair value. So I performed the "repair" myself. I re-threaded the damaged boss and replaced both O2 sensors. The CAT was visually carbon laden. The configuration of the CAT built right under the exhaust manifold made it easy to inspect with a bore scope passed through the upstream O2 sensor bung. So, before the vehicle was run, the exhaust down pipe was dropped and a used Mercedes mechanical injector was used to inject fluid into the cat via the sensor bung. It was pressurized using an old pressure painting pot. A gallon of Purple Cleaner ( 7 USD at Walmart) was warmed up and put into the paint pot and dispensed into the CAT to remove carbon. A gallon of warm Oxalic acid mix was next passed through ( 5 dollars, free shipping from Amazon ) followed by a warm Citric acid mix ( 2 dollars local grocery ) finally chased with warm De-ionized water. The exudates were caught in a plastic pan underneath the vehicle to be discarded at our local collection office. The gallon volume and the flow rate of the injector only resulted in about 40 minute pass through times. But it seemed to do the trick.

With the 2 new O2 sensors and the cleaned CAT, the code disappeared and the vehicle passed with pollution levels far below the average for passing vehicles in that year and group, for the strict CARB/AQMD region.

Understand, the use of weak organic acids was due to the desire of the original Cyprus paper to use benign products. Other acids can be used. However, understand that high heat and strong reactive acids can strip the precious catalysts from the substrate rendering the CAT useless. So, follow the procedure as closely as you can and you can be rewarded with an effective CAT again.

Last edited by RustyLugNut; 07-13-2013 at 04:07 AM.. Reason: Data.
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Old 07-31-2014, 02:00 PM   #8 (permalink)
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I wish I could thank the previous post twice.

Revisiting this report now because my CA emissions test is in August and the rules are stricter this time... I take the conclusions reported on p.197 to mean I'll get best results will come from a 2 hour soak at maybe 130* F (~50*C) with a steady, slow flow through the catalyst. For me that might mean a big pot, a thermometer, my BBQ grill, and a big spoon to stir! Thoughts? I'll buy a new CAT if this effort fails, but it seems greener and cheaper to source some Citric Acid from a farm supply or wine supply place and try this first...
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See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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Old 07-31-2014, 08:58 PM   #9 (permalink)
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I see no reason it should not work.

Quote:
Originally Posted by California98Civic View Post
I wish I could thank the previous post twice.

Revisiting this report now because my CA emissions test is in August and the rules are stricter this time... I take the conclusions reported on p.197 to mean I'll get best results will come from a 2 hour soak at maybe 130* F (~50*C) with a steady, slow flow through the catalyst. For me that might mean a big pot, a thermometer, my BBQ grill, and a big spoon to stir! Thoughts? I'll buy a new CAT if this effort fails, but it seems greener and cheaper to source some Citric Acid from a farm supply or wine supply place and try this first...
But, you do need some form of feedback to know if you have success or not. In my case, it was the simple expedient of running until the code cleared showing the downstream O2 sensor was in a cleaner environment. Some test stations have pre-test services for 20 dollars or so, but in my upscale neighborhood, they want their 50 bucks no matter what.

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