Where can I get metal high flow cats?
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C63 AMG
Where can I get metal high flow cats?
Just took a look at Brabus tuning.
They use a combination of ECU tuning, metal high flow cats and a special air filter insert to obtain 530hp.
Has anyone thought about deleting the rear cats and replacing the primaries with high flows to obtain more flow in the exhaust?? Just by doing that and removing the charcoal filter, I bet you could get an extra 20-30hp.
Anyone know a place that sells these cats and would it be easy to weld them in place of the primaries?
They use a combination of ECU tuning, metal high flow cats and a special air filter insert to obtain 530hp.
Has anyone thought about deleting the rear cats and replacing the primaries with high flows to obtain more flow in the exhaust?? Just by doing that and removing the charcoal filter, I bet you could get an extra 20-30hp.
Anyone know a place that sells these cats and would it be easy to weld them in place of the primaries?
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From: FL
'09 C63 AMG
So the C63 AMG oem stock exhaust does not already have high-flow metallic secondary cats? 
I was wondering about this since I just visited a local reputable custom exhaust shop...
https://mbworld.org/forums/3743567-post35.html
And, then here's another question...if the oem cats are not high-flow cars, would you have to replace all 4 cats (primary and secondary) with 4 high-flow cats (make make a HP/TQ gain) OR just 2 cats? Also, what if you just replaced the secondary cats with high-flow cats, but left the oem stock primary cats alone? The reason I ask is b/c it appears that ppl are making HP/TQ gains just from the 2 secondary (rear) cat delete (e.g. X-pipe, straight pipes, etc.) but leaving the 2 primary cats as is.
I was wondering about this since I just visited a local reputable custom exhaust shop...https://mbworld.org/forums/3743567-post35.html
And, then here's another question...if the oem cats are not high-flow cars, would you have to replace all 4 cats (primary and secondary) with 4 high-flow cats (make make a HP/TQ gain) OR just 2 cats? Also, what if you just replaced the secondary cats with high-flow cats, but left the oem stock primary cats alone?
The reason I ask is b/c it appears that ppl are making HP/TQ gains just from the 2 secondary (rear) cat delete (e.g. X-pipe, straight pipes, etc.) but leaving the 2 primary cats as is.
Last edited by sflgator; Oct 2, 2009 at 08:15 AM.
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From: Ashburn VA
C63
I haven't been under this car much so take this with a grain of salt. I am willing to bet the primary cats have a bung for an 02 sensor and the secondary ones do not have an 02 sensor. With that said, that is probably the reason people have been able to change their secondary cats with straight pipes without getting a CEL. Now if you decide to replace your primary cats, you have to be certain it comes equipped with a bung for your 02 sensor and preferably it is in the same location (otherwise you may need to extend wiring).
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From: FL
'09 C63 AMG
I haven't been under this car much so take this with a grain of salt. I am willing to bet the primary cats have a bung for an 02 sensor and the secondary ones do not have an 02 sensor. With that said, that is probably the reason people have been able to change their secondary cats with straight pipes without getting a CEL. Now if you decide to replace your primary cats, you have to be certain it comes equipped with a bung for your 02 sensor and preferably it is in the same location (otherwise you may need to extend wiring).
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C63 AMG
So the C63 AMG oem stock exhaust does not already have high-flow metallic secondary cats? I was wondering about this since I just visited a local reputable custom exhaust shop...
https://mbworld.org/forums/3743567-post35.html
And, then here's another question...if the oem cats are not high-flow cars, would you have to replace all 4 cats (primary and secondary) with 4 high-flow cats (make make a HP/TQ gain) OR just 2 cats? Also, what if you just replaced the secondary cats with high-flow cats, but left the oem stock primary cats alone? The reason I ask is b/c it appears that ppl are making HP/TQ gains just from the 2 secondary (rear) cat delete (e.g. X-pipe, straight pipes, etc.) but leaving the 2 primary cats as is.
I was wondering about this since I just visited a local reputable custom exhaust shop...https://mbworld.org/forums/3743567-post35.html
And, then here's another question...if the oem cats are not high-flow cars, would you have to replace all 4 cats (primary and secondary) with 4 high-flow cats (make make a HP/TQ gain) OR just 2 cats? Also, what if you just replaced the secondary cats with high-flow cats, but left the oem stock primary cats alone?
The reason I ask is b/c it appears that ppl are making HP/TQ gains just from the 2 secondary (rear) cat delete (e.g. X-pipe, straight pipes, etc.) but leaving the 2 primary cats as is.
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From: FL
'09 C63 AMG
Seriously though, it would seem that just replacing the oem stock secondary cats (or eliminating them) also produces some HP/TQ gains around +10-15WHP/+10 lb-ft RWTQ. I would think that anything to "free up" the flow some would help. I really think we need some more knowledgeable responses here from members that can attest to the type of cats on the oem stock exhaust vs. high-flow cats and/or secondary cat delete with the X-pipe or straight pipes.
Personally, I'm currently leaning to switching out my oem stock cats with high-flow cats if someone can tell me for sure that the current cats are not high-flow cats and switching to them would be an improvement. I just don't think removing any cats is a good idea, especially in an environment of increasing emissions testing and control.
Interestingly enough, although I know there are plenty of exhaust shops that would be willing to (illegally) delete the cats and put in an X-pipe or whatever in place of them, the custom exhaust shop I went to yesterday will not do that...and he's been in business at that same location for > 25 years!
They do quality work and know their ***** when it comes to custom exhausts, and he was quite impressed with the C63 AMG oem exhaust..."very well engineered by AMG" is what he said. 
He said the only thing he can see is doing high-flow SS cats (metallic inside as well) if in fact the oem cats are not high-flow already (and he doesn't know unless he removes them) and maybe the resonator delete if I wanted (which I do not after hearing ppl wanting to put their oem stock resonators back on due to the sound being too loud).
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C63 AMG
I am seriously contemplating doing this so yes, it is an ideal world for me.
It would be simple to cut off the rears cats. That is 10Hp gain right there. To change out the fronts might yield yet another 10Hp according to brabus. I just have to get the car on a lift to see how accessible the primaries are and if the sensors are not on the cat itself.
It would be simple to cut off the rears cats. That is 10Hp gain right there. To change out the fronts might yield yet another 10Hp according to brabus. I just have to get the car on a lift to see how accessible the primaries are and if the sensors are not on the cat itself.
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From: FL
'09 C63 AMG
Ok...just spoke with another source; this time, an expert on MB with plenty of experience with the oem stock C63 AMG exhaust and such. He said the oem stock cats are not the "high-flow" racing cats (with metallic substrate), so removing them for "off road" use will make the most HP/TQ gains, which btw, still is only ~ 10WHP.
I suppose they could be replaced with the real high-flow cats and still pick up some HP/TQ, but he said it's like "6 and one half dozen the other," since changing them out is still only for "off road" use" as well...so you might as well go all the way as long as you do it right.
So, I guess we've come full circle then (or at least I have), since it would seem that removing the secondary cats and replacing them with either straight pipes or the Single X-pipe (as long as the oem stock cats can be easily replaced later) would be the most beneficial in terms of power gains.
Hmmmm....decisions, decisions.
He said the oem stock cats are not the "high-flow" racing cats (with metallic substrate), so removing them for "off road" use will make the most HP/TQ gains, which btw, still is only ~ 10WHP. I suppose they could be replaced with the real high-flow cats and still pick up some HP/TQ, but he said it's like "6 and one half dozen the other," since changing them out is still only for "off road" use" as well...so you might as well go all the way as long as you do it right.
So, I guess we've come full circle then (or at least I have
), since it would seem that removing the secondary cats and replacing them with either straight pipes or the Single X-pipe (as long as the oem stock cats can be easily replaced later) would be the most beneficial in terms of power gains.Hmmmm....decisions, decisions.
Last edited by sflgator; Oct 2, 2009 at 03:39 PM.
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AMG GT-R
Wow, I never looked inside my stock primary cats as they were not cut off, but as sflgator said those are definitely not high-flow cats. I was told by MHP the primary cats are 500cpi or thereabouts. I think 500-600cpi is pretty much standard for most cars in the U.S.
The high flow cats I'm running with my setup are metallic, and 300 cpi. Inside it looks like a honeycomb, I'd say with holes about an 1/8" diameter. One big difference however, between mine and the stock cats is the diameter. As you can see the primary and secondary cats are what, 6" or so in diameter, whereas the high flows I'm running are 3", the same diameter as the mid pipes themselves. Basically, this makes them even more free flowing as with the stock cats, there is much more volume to restrict flow and also sound. Those stock cats look really restrictive.
The high flow cats I'm running with my setup are metallic, and 300 cpi. Inside it looks like a honeycomb, I'd say with holes about an 1/8" diameter. One big difference however, between mine and the stock cats is the diameter. As you can see the primary and secondary cats are what, 6" or so in diameter, whereas the high flows I'm running are 3", the same diameter as the mid pipes themselves. Basically, this makes them even more free flowing as with the stock cats, there is much more volume to restrict flow and also sound. Those stock cats look really restrictive.
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All Mercedes cats are 400cell-600cell Ceramic core cats (depending on year/chassis/model), Virtually no OEM cats are metal core simply due to cost constraints. Gains on the NA 55s is roughly 10HP/12TQ @ wheels on DD dyno. On an NA 63 the gains should be higher simply due to displacement advantage.
The best thing to do would be to run all 4 cats in high flow 300cell metal-core form. This is best for both sound quality and the environment as well. There's no reason you can't gain more power and be environmentally conscious as well. The 300-cell metal core cats won't throw a CEL and they fire up much quicker than ceramic cats so its the best of both worlds. Once you start deleting cats all together the sound can start to be obnoxious for some peoples tastes and you lose that refinement in sound (especially on the 63 AMGs which are already very sensitive to exhaust mods).
Here are 49 state legal OBD2 compliant 300-cell metal core high flow cats (not affiliated, just linking to ebay), $180 shipped for the pair:
http://cgi.ebay.com/ebaymotors/High-...Q5fAccessories
Pics of 300-cell metal cores:
Hope that helps,
~AMS~
The best thing to do would be to run all 4 cats in high flow 300cell metal-core form. This is best for both sound quality and the environment as well. There's no reason you can't gain more power and be environmentally conscious as well. The 300-cell metal core cats won't throw a CEL and they fire up much quicker than ceramic cats so its the best of both worlds. Once you start deleting cats all together the sound can start to be obnoxious for some peoples tastes and you lose that refinement in sound (especially on the 63 AMGs which are already very sensitive to exhaust mods).
Here are 49 state legal OBD2 compliant 300-cell metal core high flow cats (not affiliated, just linking to ebay), $180 shipped for the pair:
http://cgi.ebay.com/ebaymotors/High-...Q5fAccessories
Pics of 300-cell metal cores:
Hope that helps,
~AMS~
Last edited by AMS Performance; Oct 2, 2009 at 07:35 PM.
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Keep in mind though, if you do high flow primaries it may be a tight fit and you may have to redo the piping a bit and put in new O2 bungs (in roughly the same location but further spaced out). Although compared to older CLK AMGs it should be relatively easy (Ex. on W208s its very hard to do primaries due to space constraints). Secondaries are piece of cake so if you want to do it in stages do this first and see how you like the sound/performance, then you can move forward from there. Keep in mind, it does take roughly 2-4 weeks for the new cats to settle in and for the full sound transformation to occur, at first you won't notice much of a difference but it will change gradually over the coming weeks as ECU adjusts & etc.
Hope that helps,
~AMS~
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From: FL
'09 C63 AMG
No, no ECU tuning is required really. ECU should be able to adapt easily. The sound will improve significantly if you do all 4 cats but in a non intrusive way. It should be more smooth & refined with less drone/resonance compared to deleting secondaries (and definitely if you delete 2nd cats and do high flow primaries, which is essentially the loudest setup you can run except no cats at all).
Keep in mind though, if you do high flow primaries it may be a tight fit and you may have to redo the piping a bit and put in new O2 bungs (in roughly the same location but further spaced out). Although compared to older CLK AMGs it should be relatively easy (Ex. on W208s its very hard to do primaries due to space constraints). Secondaries are piece of cake so if you want to do it in stages do this first and see how you like the sound/performance, then you can move forward from there. Keep in mind, it does take roughly 2-4 weeks for the new cats to settle in and for the full sound transformation to occur, at first you won't notice much of a difference but it will change gradually over the coming weeks as ECU adjusts & etc.
Hope that helps,
~AMS~
Keep in mind though, if you do high flow primaries it may be a tight fit and you may have to redo the piping a bit and put in new O2 bungs (in roughly the same location but further spaced out). Although compared to older CLK AMGs it should be relatively easy (Ex. on W208s its very hard to do primaries due to space constraints). Secondaries are piece of cake so if you want to do it in stages do this first and see how you like the sound/performance, then you can move forward from there. Keep in mind, it does take roughly 2-4 weeks for the new cats to settle in and for the full sound transformation to occur, at first you won't notice much of a difference but it will change gradually over the coming weeks as ECU adjusts & etc.
Hope that helps,
~AMS~
1. The example of a high quality high-flow cat that you posted a link to the eBay listing (http://cgi.ebay.com/ebaymotors/High-...Q5fAccessories) shows that this particular cat is rated for an engine up to 5.9L; of course, our C63 AMG engine is just over 6.2L...would this be an issue for this particular high-flow cat?
2. Are there any advantages (over switching to high-flow cats) of just deleting the secondary cats and putting either a Single X-pipe or Straight Pipes in their place?
3. Are there high-flow cats that are bolt-on so you can easily switch back to the oem stock cats if needed (like when you sell or trade in your car)?
Thank you for your help!
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Good advice. FWIW, I know a few high-end exhaust fab guys, and they swear by HJS high flow cats out of Germany... in their experience, allegedly much higher quality than the generic fleabay stuff and less likely to pop a CEL. YMMV.
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Thanks; your info does help. A few questions though...
1. The example of a high quality high-flow cat that you posted a link to the shows that this particular cat is rated for an engine up to 5.9L; of course, our C63 AMG engine is just over 6.2L...would this be an issue for this particular high-flow cat?
2. Are there any advantages (over switching to high-flow cats) of just deleting the secondary cats and putting either a Single X-pipe or Straight Pipes in their place?
3. Are there high-flow cats that are bolt-on so you can easily switch back to the oem stock cats if needed (like when you sell or trade in your car)?
Thank you for your help!
1. The example of a high quality high-flow cat that you posted a link to the shows that this particular cat is rated for an engine up to 5.9L; of course, our C63 AMG engine is just over 6.2L...would this be an issue for this particular high-flow cat?
2. Are there any advantages (over switching to high-flow cats) of just deleting the secondary cats and putting either a Single X-pipe or Straight Pipes in their place?
3. Are there high-flow cats that are bolt-on so you can easily switch back to the oem stock cats if needed (like when you sell or trade in your car)?
Thank you for your help!
1) That's 5.9L per cat, and you would get a pair. And second off that's assuming you don't have secondaries, for secondaries its totally legal and fine to use them. Furthermore, f you use primaries & secondaries combined then its a non-issue (or even high flow secondaries with stock primaries).
2) It is not recommended to just delete cats in general, so if you can its better to always go high flow route instead (a lot less headaches & complications).
3) No, everything listed in this thread is weld in cats, all high flow cats in general are typically weld in (not that there is anything wrong with that).
4) Just b/c anything is sold on ebay does not make it crap. Mansory sells cats/headers on ebay for $10-15k, that doesn't make them crap (it does however make them overprice)
. Very few companies actually make cats, most are outsourced to companies here in the US and rebranded abroad anyways so your German cats could very well be the same. Also to state the obvious....just b/c its made in Germany does not make it superior. I wouldn't recommend a set of high flow cats unless they have been torture tested to work properly as promised. TB makes great cats for an affordable price, if you insist on buying something simply b/c its the most expensive option so be it but that does not necessarily make it the "best". But some people always convince themselves of it to justify the higher inflated price. Dozens of board members here have been using the TB cats for years now with no problems so they obviously are proven to be the best bang/buck mod out there at only $180 a pair. hope that helps.
Last edited by AMS Performance; Oct 3, 2009 at 12:13 AM.
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From: FL
'09 C63 AMG
1) That's 5.9L per cat, and you would get a pair. And second off that's assuming you don't have secondaries, for secondaries its totally legal and fine to use them. Furthermore, f you use primaries & secondaries combined then its a non-issue (or even high flow secondaries with stock primaries).
2) It is not recommended to just delete cats in general, so if you can its better to always go high flow route instead (a lot less headaches & complications).
3) No, everything listed in this thread is weld in cats, all high flow cats in general are typically weld in (not that there is anything wrong with that).
4) Just b/c anything is sold on ebay does not make it crap. Mansory sells cats/headers on ebay for $10-15k, that doesn't make them crap (it does however make them overprice) . Very few companies actually make cats, most are outsourced to companies here in the US and rebranded abroad anyways so your German cats could very well be the same. Also to state the obvious....just b/c its made in Germany does not make it superior. I wouldn't recommend a set of high flow cats unless they have been torture tested to work properly as promised. TB makes great cats for an affordable price, if you insist on buying something simply b/c its the most expensive option so be it but that does not necessarily make it the "best". But some people always convince themselves of it to justify the higher inflated price. Dozens of board members here have been using the TB cats for years now with no problems so they obviously are proven to be the best bang/buck mod out there at only $180 a pair.
hope that helps.
2) It is not recommended to just delete cats in general, so if you can its better to always go high flow route instead (a lot less headaches & complications).
3) No, everything listed in this thread is weld in cats, all high flow cats in general are typically weld in (not that there is anything wrong with that).
4) Just b/c anything is sold on ebay does not make it crap. Mansory sells cats/headers on ebay for $10-15k, that doesn't make them crap (it does however make them overprice)
. Very few companies actually make cats, most are outsourced to companies here in the US and rebranded abroad anyways so your German cats could very well be the same. Also to state the obvious....just b/c its made in Germany does not make it superior. I wouldn't recommend a set of high flow cats unless they have been torture tested to work properly as promised. TB makes great cats for an affordable price, if you insist on buying something simply b/c its the most expensive option so be it but that does not necessarily make it the "best". But some people always convince themselves of it to justify the higher inflated price. Dozens of board members here have been using the TB cats for years now with no problems so they obviously are proven to be the best bang/buck mod out there at only $180 a pair. hope that helps.
Also, why do you say that it's generally bad to delete the secondary cats?
It would seem that many companies and tuners go this route on the C63 AMG...RENNtech (they offer their cat deleting straight pipe), MHP (catless long tube headers), etc. AND we haven't heard of any issues thus far. Isn't that b/c the O2 sensors are just behind the primary cats and the secondary cats have nothing...no CELS or other issues. I was under the impression that either replacing the secondary cats with high-flow cats vs. cat delete w/ X-pipe or straight pipes is like "6 and one half dozen the other." Is this not true?
btw -- the $180/pair high-flow cats you pointed us to on eBay...are they a "universal" fit? It seems like this small muffler guy specializes in truck exhausts; do you know if this particular high-flow cat (w/ 2.5" inlet/outlet) will fit correctly on the C63 AMG exhaust?
Last edited by sflgator; Oct 3, 2009 at 12:28 AM.
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Thanks for answering...definitely helps!
Also, why do you say that it's generally bad to delete the secondary cats? It would seem that many companies and tuners go this route on the C63 AMG...RENNtech (they offer their cat deleting straight pipe), MHP (catless long tube headers), etc. AND we haven't heard of any issues thus far. Isn't that b/c the O2 sensors are just behind the primary cats and the secondary cats have nothing...no CELS or other issues.
I was under the impression that either replacing the secondary cats with high-flow cats vs. cat delete w/ X-pipe or straight pipes is like "6 and one half dozen the other." Is this not true?
btw -- the $180/pair high-flow cats you pointed us to on eBay...are they a "universal" fit? It seems like this small muffler guy specializes in truck exhausts; do you know if this particular high-flow cat (w/ 2.5" inlet/outlet) will fit correctly on the C63 AMG exhaust?
Also, why do you say that it's generally bad to delete the secondary cats?
It would seem that many companies and tuners go this route on the C63 AMG...RENNtech (they offer their cat deleting straight pipe), MHP (catless long tube headers), etc. AND we haven't heard of any issues thus far. Isn't that b/c the O2 sensors are just behind the primary cats and the secondary cats have nothing...no CELS or other issues. I was under the impression that either replacing the secondary cats with high-flow cats vs. cat delete w/ X-pipe or straight pipes is like "6 and one half dozen the other." Is this not true?
btw -- the $180/pair high-flow cats you pointed us to on eBay...are they a "universal" fit? It seems like this small muffler guy specializes in truck exhausts; do you know if this particular high-flow cat (w/ 2.5" inlet/outlet) will fit correctly on the C63 AMG exhaust?
Due to legal reasons I cannot actively condone or encourage the removal emissions equipment, which is why I say that. Its not bad from a performance standpoint or a dangerous standpoint or anything like that. Its more a ethical/legal issue, and most importantly, and environmental one. Having a second set of cats does help clean up the emissions significantly. Anyone can make power simply by deleting cats, the real challenge lies in making more power without drastically increasing the vehicle's emissions.
I'm not sure what you mean by 6", can you clarify
The cats linked are universal fit correct, you would have to weld them in. They also come in 3.0" which may be a better fit for the 63s due to their larger piping. For the older NA 55s the 2.5" are proper size. There's no difference in price. You can also get the 2.5s" and have the exhaust shop expand them out exactly to the right size so they can sleeve it onto the OEM piping for the best fit. How you chose to do it is totally up to you.
Hope that helps
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From: FL
'09 C63 AMG
Due to legal reasons I cannot actively condone or encourage the removal emissions equipment, which is why I say that. Its not bad from a performance standpoint or a dangerous standpoint or anything like that. Its more a ethical/legal issue, and most importantly, and environmental one. Having a second set of cats does help clean up the emissions significantly. Anyone can make power simply by deleting cats, the real challenge lies in making more power without drastically increasing the vehicle's emissions.
I'm not sure what you mean by 6", can you clarify
The cats linked are universal fit correct, you would have to weld them in. They also come in 3.0" which may be a better fit for the 63s due to their larger piping. For the older NA 55s the 2.5" are proper size. There's no difference in price. You can also get the 2.5s" and have the exhaust shop expand them out exactly to the right size so they can sleeve it onto the OEM piping for the best fit. How you chose to do it is totally up to you.
Hope that helps
I'm not sure what you mean by 6", can you clarify
The cats linked are universal fit correct, you would have to weld them in. They also come in 3.0" which may be a better fit for the 63s due to their larger piping. For the older NA 55s the 2.5" are proper size. There's no difference in price. You can also get the 2.5s" and have the exhaust shop expand them out exactly to the right size so they can sleeve it onto the OEM piping for the best fit. How you chose to do it is totally up to you.
Hope that helps
Oh, and all I meant by the "6 and 1/2 dozen the other" is just that the cat delete vs. replacing w/ high-flow cats will basically yield similar results, so it's more a toss up in terms of some HP/TQ gains.
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Yes; that all helps...thanks. I was under the impression that the C63 AMG has 2.5" piping...so, it's actually 3" piping where the secondary cats are?
Oh, and all I meant by the "6 and 1/2 dozen the other" is just that the cat delete vs. replacing w/ high-flow cats will basically yield similar results, so it's more a toss up in terms of some HP/TQ gains.
Oh, and all I meant by the "6 and 1/2 dozen the other" is just that the cat delete vs. replacing w/ high-flow cats will basically yield similar results, so it's more a toss up in terms of some HP/TQ gains.
High flow 300cell metal cats will get you roughly 70%HP/TQ of a full cat delete with none of the downsides/drawbacks so you don't sacrifice that much by maintaining high flow cats vs. cat delete. Also, you don't have to worry about back pressure dropping too much which would potentially hurt low end torque (more of an issue with primaries than secondaries).
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From: FL
'09 C63 AMG
If the stock piping is 2.75" then get the 3.0", If the stock piping is dual 2.25, then get the 2.5" (NA 55s).
High flow 300cell metal cats will get you roughly 70%HP/TQ of a full cat delete with none of the downsides/drawbacks so you don't sacrifice that much by maintaining high flow cats vs. cat delete. Also, you don't have to worry about back pressure dropping too much which would potentially hurt low end torque (more of an issue with primaries than secondaries).
High flow 300cell metal cats will get you roughly 70%HP/TQ of a full cat delete with none of the downsides/drawbacks so you don't sacrifice that much by maintaining high flow cats vs. cat delete. Also, you don't have to worry about back pressure dropping too much which would potentially hurt low end torque (more of an issue with primaries than secondaries).
Now, I just need to find out exactly the size inlet/outlet needed.
