HOLLOW OUT A CAT?
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Joined: Aug 2009
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From: Ann Arbor, MI
03 SL55 AMG, 02 ML500 & 95 C36 AMG
HOLLOW OUT A CAT?
Hey guys my friend has a 2006 C55 AMG and his primary cats were toast. Instead of replacing the cats he just dropped the whole system on the floor and hollowed the cats out and welded it. I must admit is sounds so much better.
He kind of tempted me to do the same but I am very hesitant. I do not want to throw any codes. We do not have emissions in Michigan so it would never really be a problem. Would do something like this cause any damage or throw any codes? My friend is such an *******
lol. He keeps pushing me to do it but I keep telling him no.
He kind of tempted me to do the same but I am very hesitant. I do not want to throw any codes. We do not have emissions in Michigan so it would never really be a problem. Would do something like this cause any damage or throw any codes? My friend is such an *******
lol. He keeps pushing me to do it but I keep telling him no.
Senior Member
Joined: Nov 2010
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2002 C32 AMG
If you destroy your cat it would probably throw a code.
What you should do if you want to go cat less is remove your functional cat and replace with a straight through pipe, it shouldn't cost much too. You then have the option to revert.
What you should do if you want to go cat less is remove your functional cat and replace with a straight through pipe, it shouldn't cost much too. You then have the option to revert.
Thread Starter
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Joined: Aug 2009
Posts: 147
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From: Ann Arbor, MI
03 SL55 AMG, 02 ML500 & 95 C36 AMG
Back on topic lol my friend actually did a pretty clean job. He cut the Cat from the top with small fine cuts and then welded it nice and clean. You could never tell that he hollowed out his cat.
By the way it sounds so bad ***!
By the way it sounds so bad ***!
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Super Member
Joined: Oct 2008
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From: seattle
1990 300ce supercharged and intercooled
I would cut the cats out completely and sell them instead of gutting them. Or have a new exhaust made and sell the whole thing. Factory cats cost about 5-600 or more per side. You can also just sell them for the precious metal for about 2-400 for all of them depending on the current price.
Thread Starter
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Joined: Aug 2009
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From: Ann Arbor, MI
03 SL55 AMG, 02 ML500 & 95 C36 AMG
I think that would be the best way to go if your going to delete your primary cats. I asked my buddy why he did not go that route. He said you would have to bend whatever pipe that would take the place of the cat. My buddy was in a rush so he really did not care about selling the cats 
.
.
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From: SCV SoCal
2002 CLK430
If I understand this correctly, your friend has hollowed out both primary (closest to the engine) cats and he hasn’t gotten a CEL. Does he have a US spec car? If so, does his CEL work? The reason I ask is US spec cars have primary and secondary oxygen sensors. The ECU compares the signal from those sensors. If the cat is hollowed out or a straight pipe is used, the reading won’t differ very much and the ECU will record that as a P04nn OBDII failure (catalyst system efficiency below threshold). This will light up the CEL. There are ways around this. One way is to get a tuner or a dealer to turn off the secondary O2 sensors (a dealer won’t, but they "can"). You could 'fix' the secondary sensor reading problem yourself, but your post didn’t mention this so I'm going to guess nothing other than hammering out substrate was done.
What I’m also missing is the point. Aside from ruining a perfectly good cat, it would make a low pressure zone, thereby slowing down gasses. Assuming you don’t know what I mean by this, in a nutshell the exhaust will flow worse than if a straight pipe were used. Also, there is a chance of not getting all the substrate material out of the cat. And what isn’t removed will eventually break free. Substrate chunks may work their way out of the exhaust. On the other hand, they may get stuck in one of the perforated tubes in a muffler chamber (also bad for flow).
What I’m also missing is the point. Aside from ruining a perfectly good cat, it would make a low pressure zone, thereby slowing down gasses. Assuming you don’t know what I mean by this, in a nutshell the exhaust will flow worse than if a straight pipe were used. Also, there is a chance of not getting all the substrate material out of the cat. And what isn’t removed will eventually break free. Substrate chunks may work their way out of the exhaust. On the other hand, they may get stuck in one of the perforated tubes in a muffler chamber (also bad for flow).
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From: Texas
C63 507 AMG DA Car #19
We used to do this to the old ceramic cats in the mustangs for a deeper tone..... we did not see much performance increase, but we thought we sounded cool.
I would have a "race pipe" fabbed and keep the stock h-pipe for when you get old like me and don't want the noise anymore.... or if you sell it.
GL>
I would have a "race pipe" fabbed and keep the stock h-pipe for when you get old like me and don't want the noise anymore.... or if you sell it.
GL>
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From: Ann Arbor, MI
03 SL55 AMG, 02 ML500 & 95 C36 AMG
I agree with you 100% Marcus, but his cats were toast. The material inside was completely melted. He did not have any tuning done whatsoever. His check engine light does work but has not gone off yet. Its probably too early to tell. He has been driving this way about six days with no check engine light.
He did a pretty good job making sure that no chunks were left over. That included lifting the whole system straight up into the air a few times, vacuuming the little chunks and then finally blowing air into the system to make sure that nothing was left over.
He did a pretty good job making sure that no chunks were left over. That included lifting the whole system straight up into the air a few times, vacuuming the little chunks and then finally blowing air into the system to make sure that nothing was left over.
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Joined: Aug 2009
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From: Ann Arbor, MI
03 SL55 AMG, 02 ML500 & 95 C36 AMG
I forgot to mention that the best part is when you look under the car you could never tell that the cats were touched. Unless of course you drop the whole system on the floor lol.
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From: SCV SoCal
2002 CLK430
I agree with you 100% Marcus, but his cats were toast. The material inside was completely melted. He did not have any tuning done whatsoever. His check engine light does work but has not gone off yet. Its probably too early to tell. He has been driving this way about six days with no check engine light.
He did a pretty good job making sure that no chunks were left over. That included lifting the whole system straight up into the air a few times, vacuuming the little chunks and then finally blowing air into the system to make sure that nothing was left over.
He did a pretty good job making sure that no chunks were left over. That included lifting the whole system straight up into the air a few times, vacuuming the little chunks and then finally blowing air into the system to make sure that nothing was left over.
Thread Starter
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Joined: Aug 2009
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From: Ann Arbor, MI
03 SL55 AMG, 02 ML500 & 95 C36 AMG
Your right Marcus I should probably tell him to find out why his cats went bad in the first place. To answer Betrezra question; the sound is amazing. It now sounds like a V8 should. I thought the sound would be crappy, but it is very nice.
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Joined: Aug 2009
Posts: 147
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From: Ann Arbor, MI
03 SL55 AMG, 02 ML500 & 95 C36 AMG
Well my friend called me up yesterday night and told me his check engine light is now on. He read the codes and they are P0442, P0443 catalyst . Which of course is related to his primary cats. He told me his car is driving fine with no problems.
Is he in for a rude awakening?
Is he in for a rude awakening?
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From: SCV SoCal
2002 CLK430
The plug non fouler approach works for worn cats (washed out washcoat), but I have never heard of it working with zero catalyst material. At this point the options that come to mind are (1) turning off the rear sensors or (2) installing metal substrate cats. There are other options, buy those two are simple.
