Cat question..
Thread Starter
MBWorld Fanatic!
Joined: Mar 2007
Posts: 2,155
Likes: 14
From: Sydney, Australia
Vath ML63 Brabus C63 SL63 CLK63BS C63BS
Cat question..
I assume the primary cat set up on the C63 black series is same as stock but if I replace the primaries with hi flow cats do I need to modify the 02 sensors or do they plug into pipe ahead of primary cats. I basically want to cut and paste in hi flow cats but want to know if I need to relocate O2 sensors before I head down to exhaust shop and get car on hoist.
Thread Starter
MBWorld Fanatic!
Joined: Mar 2007
Posts: 2,155
Likes: 14
From: Sydney, Australia
Vath ML63 Brabus C63 SL63 CLK63BS C63BS
No matter, question answered already. 02 sensor in front and behind primary cat. Been advised I will need to either a) tune engine to account fo hi flowing cat or b) fool the computer with an insert into the rear 02 sensor that will make computer think exhaust gases had retained their previous velocity/temp. Changed my mind and now putting in a different resonator to see if I can get the effect I am looking for - which. Is even more crackling and popping and a fraction more volume. Changing cats wasn't going to do that anyway apparently so all good.
MBWorld Fanatic!
Joined: Mar 2011
Posts: 1,601
Likes: 10
From: San Diego/San Francisco
AMG GLC63. Audi R8
It depends on the tune and the cats. If the surface area of the cats is the same (ie if a large 100 cell cat has the same surface area of a small 400 cell cat) your O2 sensor should not know the difference. A tune needs to take into account the flow volume of the cats in addition to its cell count. Most tuners will ask you what other mods you have done to your car and adjust the tune accordingly.
Thread Starter
MBWorld Fanatic!
Joined: Mar 2007
Posts: 2,155
Likes: 14
From: Sydney, Australia
Vath ML63 Brabus C63 SL63 CLK63BS C63BS
Well the stock cats are very large in diameter and look to be 500/600 cell having seen inside them today. The cats I was contemplating were probably half the diameter and 200 cell.
I had to scratch my itch so I removed the rear resonator fabricated by Sebring and put in ones fabbed by Mille Miglia. The 1 foot long Sebring resonator has two distinct tubes inside with a small hole in each pipe towards the back of them connecting the two chambers, basically a cross pipe. There is also a small area of perforation inside each chamber but 60% of the length of each chamber is smooth. The new ones I had installed are not connected and have more perforations. The net effect of this is a slight increase in volume, slightly deeper note, no drone and a bit more of the warbling/throatiness on overrun & downshifting that other Black Series owners will be familiar with.
All in all it's toughened the sound up a notch further but had less of an overall effect than removing the secondary cats did. That particular step had a great impact on sound, yielding a deeper note and more crackle & pop.
I have been thinking about it all afternoon on bondi beach and I think electric cutouts might be the next step...
I had to scratch my itch so I removed the rear resonator fabricated by Sebring and put in ones fabbed by Mille Miglia. The 1 foot long Sebring resonator has two distinct tubes inside with a small hole in each pipe towards the back of them connecting the two chambers, basically a cross pipe. There is also a small area of perforation inside each chamber but 60% of the length of each chamber is smooth. The new ones I had installed are not connected and have more perforations. The net effect of this is a slight increase in volume, slightly deeper note, no drone and a bit more of the warbling/throatiness on overrun & downshifting that other Black Series owners will be familiar with.
All in all it's toughened the sound up a notch further but had less of an overall effect than removing the secondary cats did. That particular step had a great impact on sound, yielding a deeper note and more crackle & pop.
I have been thinking about it all afternoon on bondi beach and I think electric cutouts might be the next step...
Last edited by Maverick1975; Jan 7, 2013 at 02:21 AM.
Super Member
Joined: Jul 2011
Posts: 938
Likes: 1
From: D.c
2009 Barolo red C63 AMG (SOLD).13' P31 c63 coupe 2012 porsche panamera
Who said cats doesn't make more popping sounds? My 09 with straight pipes instead of the resonators sounded like stock but on roids, not as loud as LTH but DEFINITELY way more pops and crackles. I just removed my primaries, and the exhaust crackles and pops when i let off the gas after 1.5 rpm. Even if im at 10 MPH itll crackle and pop tons when it slows down to 0. Sounds like gun shots 
Thread Starter
MBWorld Fanatic!
Joined: Mar 2007
Posts: 2,155
Likes: 14
From: Sydney, Australia
Vath ML63 Brabus C63 SL63 CLK63BS C63BS
Who said cats doesn't make more popping sounds? My 09 with straight pipes instead of the resonators sounded like stock but on roids, not as loud as LTH but DEFINITELY way more pops and crackles. I just removed my primaries, and the exhaust crackles and pops when i let off the gas after 1.5 rpm. Even if im at 10 MPH itll crackle and pop tons when it slows down to 0. Sounds like gun shots
Was it dramatically louder with no resonators, surely there must have been more drone?? Maybe I just chop out res altogether and just run primary cats??
Or go cutouts to control volume better, my neighbours freaking hate me as it is...
Super Member
Joined: Jul 2011
Posts: 938
Likes: 1
From: D.c
2009 Barolo red C63 AMG (SOLD).13' P31 c63 coupe 2012 porsche panamera
So you have no resonators AND no cats?? Did you retune because apparently the ecu will be expecting to see significantly slower exhaust gases pass the second of the 2 O2 sensors. Thought you might have gotten a CEL.
Was it dramatically louder with no resonators, surely there must have been more drone?? Maybe I just chop out res altogether and just run primary cats??
Or go cutouts to control volume better, my neighbours freaking hate me as it is...
Was it dramatically louder with no resonators, surely there must have been more drone?? Maybe I just chop out res altogether and just run primary cats??
Or go cutouts to control volume better, my neighbours freaking hate me as it is...
Go with the resonators first, then the secondaries if thats not enough for ya, thats if you dont mind chopping off your exhaust.
Trending Topics
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Super Member
Joined: Sep 2012
Posts: 533
Likes: 5
C63 Coupe
Well the stock cats are very large in diameter and look to be 500/600 cell having seen inside them today. The cats I was contemplating were probably half the diameter and 200 cell.
I had to scratch my itch so I removed the rear resonator fabricated by Sebring and put in ones fabbed by Mille Miglia. The 1 foot long Sebring resonator has two distinct tubes inside with a small hole in each pipe towards the back of them connecting the two chambers, basically a cross pipe. There is also a small area of perforation inside each chamber but 60% of the length of each chamber is smooth. The new ones I had installed are not connected and have more perforations. The net effect of this is a slight increase in volume, slightly deeper note, no drone and a bit more of the warbling/throatiness on overrun & downshifting that other Black Series owners will be familiar with.
All in all it's toughened the sound up a notch further but had less of an overall effect than removing the secondary cats did. That particular step had a great impact on sound, yielding a deeper note and more crackle & pop.
I have been thinking about it all afternoon on bondi beach and I think electric cutouts might be the next step...
I had to scratch my itch so I removed the rear resonator fabricated by Sebring and put in ones fabbed by Mille Miglia. The 1 foot long Sebring resonator has two distinct tubes inside with a small hole in each pipe towards the back of them connecting the two chambers, basically a cross pipe. There is also a small area of perforation inside each chamber but 60% of the length of each chamber is smooth. The new ones I had installed are not connected and have more perforations. The net effect of this is a slight increase in volume, slightly deeper note, no drone and a bit more of the warbling/throatiness on overrun & downshifting that other Black Series owners will be familiar with.
All in all it's toughened the sound up a notch further but had less of an overall effect than removing the secondary cats did. That particular step had a great impact on sound, yielding a deeper note and more crackle & pop.
I have been thinking about it all afternoon on bondi beach and I think electric cutouts might be the next step...
I'm curious because my c63 is currently in the shop for a quaife LSD and secondary cat delete we are going to be chopping off 2nd cats and replacing with 2 12inch straight pipe resonated bullets. Hopefully it sounds good
Thread Starter
MBWorld Fanatic!
Joined: Mar 2007
Posts: 2,155
Likes: 14
From: Sydney, Australia
Vath ML63 Brabus C63 SL63 CLK63BS C63BS
So I dont get what your setup exactly is? You just had your secondary cats removed and replaced with a resonated cross pipe than switched that to a resonated straight pipe?
I'm curious because my c63 is currently in the shop for a quaife LSD and secondary cat delete we are going to be chopping off 2nd cats and replacing with 2 12inch straight pipe resonated bullets. Hopefully it sounds good
I'm curious because my c63 is currently in the shop for a quaife LSD and secondary cat delete we are going to be chopping off 2nd cats and replacing with 2 12inch straight pipe resonated bullets. Hopefully it sounds good
