Cats or no cats, that is the question
Thread Starter
Senior Member
Joined: Mar 2009
Posts: 394
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From: Knoxville, TN
E55, Supercharged Z4 (sold)
Cats or no cats, that is the question
So I was gonna just have straight pipes back to stock mufflers once I put my headers on but then I read this thread.
https://mbworld.org/forums/w211-amg/...akes-best.html
Post 19 says this:
Now I'm thinking of just keeping the secondary cats but leaving the rest off. Primary cats are gone for sure, that's not an issue but does anybody else have any data or experience with this?
This was the only first hand knowledge I could find realted to this.
https://mbworld.org/forums/w211-amg/...akes-best.html
Post 19 says this:
My car already had the Kleemann headers with no primaries. When I removed my secondaires, I lost 2 tenths. With my hi-flows now in place of the secondaries, my car picked up the power I lost due to a little more backpressure which these engines apparently like a little of.
This was the only first hand knowledge I could find realted to this.
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From: Valley of the Sun, Arizona
C63, SL55, E55, CLS55, ML63, C55
Your best bet, depends on your needs. You seem like the type who will worry about emissions later on down the road. If you dont "Tune" for the Emissions CEL It will always be there. However this is just that, an emissions CEL. It does not control fueling to the engine like the front o2 sensors do.
From chopping up a few AMG exhaust in my day including my old C55 and now SL55. I would do this, if I was you. cut out the primary cats, leave the secondary cats, and then chop the resonators out. Then see how you like it.. Listen for drone in the cabin. If you can live with some drone or its not loud enough, chop the 2nd cats out. I thought I could live with some drone, but my old C55 just about crushed my skull from drone.
Remember this, There are no real race cars that run cats... there must be a reason or two.
You could always get a resonated xpipe to use in place of the secondary cats. Something I'm considering.
From chopping up a few AMG exhaust in my day including my old C55 and now SL55. I would do this, if I was you. cut out the primary cats, leave the secondary cats, and then chop the resonators out. Then see how you like it.. Listen for drone in the cabin. If you can live with some drone or its not loud enough, chop the 2nd cats out. I thought I could live with some drone, but my old C55 just about crushed my skull from drone.
Remember this, There are no real race cars that run cats... there must be a reason or two.
You could always get a resonated xpipe to use in place of the secondary cats. Something I'm considering.
Thread Starter
Senior Member
Joined: Mar 2009
Posts: 394
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From: Knoxville, TN
E55, Supercharged Z4 (sold)
Thanks Hooley. I actually don't care at all about emissions and neither does the state of TN. No inspections, smog tests or anything like that over here.
I just want to do what makes the most amount of power. I thought about the fact that race cars do not run any cats but after reading that post it obviously made me think. I was hoping somebody had factual evidence that could help with my decision.
From what I understand there is little to no drone with this setup if you keep the stock mufflers in place so I think I'm good there. If it did get loud I'd look into a resonator to keep that in check. Should be fairly straight forward.
Maybe, just maybe I can do a before and after dyno with secondary cats in and then out but I'm kind of doubting that for time reasons. I'll more then likely just roll in with a given setup, get it dyno tuned and then go out and kill some polar bears.
Thanks guys!
I just want to do what makes the most amount of power. I thought about the fact that race cars do not run any cats but after reading that post it obviously made me think. I was hoping somebody had factual evidence that could help with my decision.
From what I understand there is little to no drone with this setup if you keep the stock mufflers in place so I think I'm good there. If it did get loud I'd look into a resonator to keep that in check. Should be fairly straight forward.
Maybe, just maybe I can do a before and after dyno with secondary cats in and then out but I'm kind of doubting that for time reasons. I'll more then likely just roll in with a given setup, get it dyno tuned and then go out and kill some polar bears.
Thanks guys!
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'03 E55, Range Rover Sport Supercharged, Ducati 748R
i've tested secocondary cats vs straight pipes at the track and ali's statement is as bottom line as it gets. don't remove your cats unless you plan on tuning the lost tq back into the equation.
Thread Starter
Senior Member
Joined: Mar 2009
Posts: 394
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From: Knoxville, TN
E55, Supercharged Z4 (sold)
Thanks Mike and Ali! I'm stock now and would be getting a tune on whatever setup I show up with if that makes sense. So if straight pipes is the way to go for more power then that's what I'll do.
Thanks guys.
Thanks guys.
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S65
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'03 E55, Range Rover Sport Supercharged, Ducati 748R
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From: Texas
2003 CL55
So I was gonna just have straight pipes back to stock mufflers once I put my headers on but then I read this thread.
https://mbworld.org/forums/w211-amg/...akes-best.html
Post 19 says this:
Now I'm thinking of just keeping the secondary cats but leaving the rest off. Primary cats are gone for sure, that's not an issue but does anybody else have any data or experience with this?
This was the only first hand knowledge I could find realted to this.
https://mbworld.org/forums/w211-amg/...akes-best.html
Post 19 says this:
Now I'm thinking of just keeping the secondary cats but leaving the rest off. Primary cats are gone for sure, that's not an issue but does anybody else have any data or experience with this?
This was the only first hand knowledge I could find realted to this.
I would leave your AMG cats and pipes in tact and build a new mid pipe with RACE cats.. Never know when you may need the stock system and they are damn expensive to replace..
The power loss with a 3" mid pipe and good headers is un-noticable,,,,, if any.... Even if it is 5hp, you can hardly dyno these engines that close to be sure.. I dynoed against several cars with no cats , same list of mods, same dyno (pulley, tune, 82mm TB and headers) and they still make less power.. Paying attention to details , will net you more HP/TQ and keep the opulence in your ride.. Just Say "NO to DRONE"!!!
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E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
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E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
CL55 UPD Cold Air Boost kit, UPD 3000 stall converter, UPD 77mm SC clutched pulley and beltwrap kit, Custom long tubes, UPD crank pulley , UPD suspension kit, UPD SC pulley, Aux. HE, Trunk tank w/rule 2000 pump, Mezeire pump, UPD 5pc idler set, Aluminum rotor hats.
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instagram @ultimate_pd
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From: Clifton, NJ
96 and 08 911 turbos
Do you really want your late model amg to smell like a 60s camaro? Do you want to smell exhaust when you come to a stop with the windows open?
I had a catless car for years. It sucked.
As to race cars not having cats, thats a silly statement. An E55 is not a race car. Race cars are WOT for hours at a time. I can't think of many cat elements that could stand up to that...regardless of whether they robbed a few hp.
Go to aftermarket cats if you want, but don't remove them in total.
I had a catless car for years. It sucked.
As to race cars not having cats, thats a silly statement. An E55 is not a race car. Race cars are WOT for hours at a time. I can't think of many cat elements that could stand up to that...regardless of whether they robbed a few hp.
Go to aftermarket cats if you want, but don't remove them in total.
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From: Northern VA
2006 E55
I have to agree with the pro cat crowd.
Not only do SC engines like a little back pressure, but I believe the minimal gains to be had are not worth the down sides....are you really going to notice 5whp in this car?
If ultimate power is your criteria then replace the primary cat with a high flow cat, which have been proven to damn near match the flow of a cat delete while still keeping you legal, quiet and stink free.
Besides I personaly believe the E55 is a refined car and should not sound and smell like a hot rod Camaro.
And I know I am going to get flamed for this but I also consider the fact that I have a small social responsibility not to stink out my fellow drivers with a polution belching exhaust. And while prosecution is unlikely, removing your cats is a federal offense with retarded potential fines, something I can't help but think about.
Rant over...lol.
Not only do SC engines like a little back pressure, but I believe the minimal gains to be had are not worth the down sides....are you really going to notice 5whp in this car?
If ultimate power is your criteria then replace the primary cat with a high flow cat, which have been proven to damn near match the flow of a cat delete while still keeping you legal, quiet and stink free.
Besides I personaly believe the E55 is a refined car and should not sound and smell like a hot rod Camaro.
And I know I am going to get flamed for this but I also consider the fact that I have a small social responsibility not to stink out my fellow drivers with a polution belching exhaust. And while prosecution is unlikely, removing your cats is a federal offense with retarded potential fines, something I can't help but think about.
Rant over...lol.
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From: NJ/Greece
2006 CLS55 & 2002 SL55 (R129) Silver Arrow
I tried removing my secondary cats and I felt it weakend my low end torque (butt dyno). I decided to put them back a week later (not to mention the drone was giving me a migraine).
I agree, the blown M113's like the back pressure for low end torque.
I agree, the blown M113's like the back pressure for low end torque.
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S65
I've NEVER had a car that had cats on it after I was done with it. Personally, I don't think the "smell" is all that bad. I noticed a tinge of it after running the cars hard. Other than that... nada.
Furthermore, I have NEVER had anyone comment on any funky smells coming out of the exhaust.
Your nose mileage may vary, though.
Furthermore, I have NEVER had anyone comment on any funky smells coming out of the exhaust.
Your nose mileage may vary, though.
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From: Florida-Germany-New York
2004 E55,1969 300SEL6.3,2011 ML350 BlueTec Diesel,2005 ML400 CDI
As most of you all probably know, great care must be used when selecting the length and diameter of the primary tubes. Tubes that are too large will cause the exhaust gas to expand and slow down, decreasing the scavenging effect. Tubes that are too small will create backpressure against which the engine must work to expel the exhaust gas from the chamber, reducing power and leaving exhaust in the chamber to dilute the incoming intake charge. Since engines produce more exhaust gas at higher speeds, the header(s) are tuned to a particular engine speed range according to the intended application. Typically, large primary tubes offer the best gains in power and torque at higher engine speeds, while smaller tubes offer the best gains at lower speeds such as the 113.
Many headers are also resonance tuned, to utilize the low-pressure reflected wave rarefaction pulse which can help scavenging the combustion chamber during valve overlap. This pulse is created in all exhaust systems each time a change in density occurs, such as when exhaust merges into the collector. For clarification, the rarefaction pulse is the technical term for the same process that was described above in the "head, body, tail" description. By tuning the length of the primary tubes, usually by means of resonance tuning, the rarefaction pulse can be timed to coincide with the exact moment valve overlap occurs. Do not think for a moment that the CATS on an E55 are randomly located. Rarefaction calculations indicate that these CATS are precisely located to generate a proper pulse. Also, calculations would indicate that a 3" pipe is too large.
Many headers are also resonance tuned, to utilize the low-pressure reflected wave rarefaction pulse which can help scavenging the combustion chamber during valve overlap. This pulse is created in all exhaust systems each time a change in density occurs, such as when exhaust merges into the collector. For clarification, the rarefaction pulse is the technical term for the same process that was described above in the "head, body, tail" description. By tuning the length of the primary tubes, usually by means of resonance tuning, the rarefaction pulse can be timed to coincide with the exact moment valve overlap occurs. Do not think for a moment that the CATS on an E55 are randomly located. Rarefaction calculations indicate that these CATS are precisely located to generate a proper pulse. Also, calculations would indicate that a 3" pipe is too large.
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2006 E55 AMG
Hey Luke, I have Chris's system and have zero cats, no resonator, X-pipe, and stock mufflers. I was once on the fence like yourself but after endless conversations with Chiromikey I was finally convinced. My biggest fear was DRONE, glad to report that I have none what so ever. A few members here have been in my car and I'm sure they'll all tell ya how quiet my car is inside, almost too quiet. Let's see - Mikesamg (the most), Chiromikey, MB_forever, Hammer Down, and Sneakyneon.
Performance....
My other fear was loss of torque and raising my 60' times. I definitely don't feel any loss of torque and I haven't been given the opportunity to test my 60' times on a well prepped track. My last outing track prep sucked but I was still able to pull off a 1.642 with traction loss. If I had to guess, which I don't like to but I will, I feel my car has more torque than before. Unfortunately I won't have an answer for you until later on this year when TNT moves back to days. Both Mo, Nick, and Mike will vouch that my car is very strong right now and it pulls very hard all the way up to red line. I'm also running about .6 rich consistently but better safe then sorry on the streets. Once I get more seat time, runs, and better logs at the track I'll have Jeremy remove some fuel if I feel needed.
You have my contact info Luke so please feel free to contact me anytime.
Performance....
My other fear was loss of torque and raising my 60' times. I definitely don't feel any loss of torque and I haven't been given the opportunity to test my 60' times on a well prepped track. My last outing track prep sucked but I was still able to pull off a 1.642 with traction loss. If I had to guess, which I don't like to but I will, I feel my car has more torque than before. Unfortunately I won't have an answer for you until later on this year when TNT moves back to days. Both Mo, Nick, and Mike will vouch that my car is very strong right now and it pulls very hard all the way up to red line. I'm also running about .6 rich consistently but better safe then sorry on the streets. Once I get more seat time, runs, and better logs at the track I'll have Jeremy remove some fuel if I feel needed.
You have my contact info Luke so please feel free to contact me anytime.
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From: merryland
cornfed gtr and m3
I am running 2.75" straight exhaust with x-pipe and stock mufflers. I have absolutely no drone and have no smell. The car is very quiet at idle and low rpm, but beastly at WOT! Currently with Kleemann headers but that will be changing shortly... 
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Whatever we're tuning!
More secrets?
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From: Florida-Germany-New York
2004 E55,1969 300SEL6.3,2011 ML350 BlueTec Diesel,2005 ML400 CDI
Stronger with CATS in place. Be sure to match the CAT inlet size to match the outlet size). Factory CAT location will generate the proper rarefaction pulse (This pulse cannot pass through the CATS). However, replacing the secondary CATS with a properly sized X-Pipe w/expansion chamber can yield additional HP gains above 4500 RPM, but don't expect more than 1%-3%.
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'18 AMG GTR, '04 CL55, '04 E55, '03 CLK500, '01 E55,94 E500, '91 190E 2.5-16 EVOII, '86 560SL
Hey Luke, I have Chris's system and have zero cats, no resonator, X-pipe, and stock mufflers. I was once on the fence like yourself but after endless conversations with Chiromikey I was finally convinced. My biggest fear was DRONE, glad to report that I have none what so ever. A few members here have been in my car and I'm sure they'll all tell ya how quiet my car is inside, almost too quiet. Let's see - Mikesamg (the most), Chiromikey, MB_forever, Hammer Down, and Sneakyneon.
Performance....
My other fear was loss of torque and raising my 60' times. I definitely don't feel any loss of torque and I haven't been given the opportunity to test my 60' times on a well prepped track. My last outing track prep sucked but I was still able to pull off a 1.642 with traction loss. If I had to guess, which I don't like to but I will, I feel my car has more torque than before. Unfortunately I won't have an answer for you until later on this year when TNT moves back to days. Both Mo, Nick, and Mike will vouch that my car is very strong right now and it pulls very hard all the way up to red line. I'm also running about .6 rich consistently but better safe then sorry on the streets. Once I get more seat time, runs, and better logs at the track I'll have Jeremy remove some fuel if I feel needed.
You have my contact info Luke so please feel free to contact me anytime.
Performance....
My other fear was loss of torque and raising my 60' times. I definitely don't feel any loss of torque and I haven't been given the opportunity to test my 60' times on a well prepped track. My last outing track prep sucked but I was still able to pull off a 1.642 with traction loss. If I had to guess, which I don't like to but I will, I feel my car has more torque than before. Unfortunately I won't have an answer for you until later on this year when TNT moves back to days. Both Mo, Nick, and Mike will vouch that my car is very strong right now and it pulls very hard all the way up to red line. I'm also running about .6 rich consistently but better safe then sorry on the streets. Once I get more seat time, runs, and better logs at the track I'll have Jeremy remove some fuel if I feel needed.
You have my contact info Luke so please feel free to contact me anytime.
Which brand?
Do you have any pictures of your exahust system seeing it from under the car?
Im installing right now a set of LT headers, planing to remove all of the CATS, resonators but leaving the stock rear mufflers untouched.
But after reading all this, Im worried to have a lot of sound inside of the car, and that the car would sound like an old tow truck.
Does your car sound too loud outside that can be heard blocks away?
How about inside the cabin?
I havent decided what to do and my exahust system is about to get all chop and cut.
I just installed a 180 pulley, 82tb, cf air intake, and a ECU tune for all of this mods, plus NO cats.
Im not planing to race my car on a race track, just want to have a very strong car for the streets, but still want to keeps its Luxury car use and confort.
What would you advice me?
