C55 exhaust mod question
So I have a question, and I'm sorry in advance if its been answered before. I saw several threads pertaining to it, but none of them cleared it up for me. I'm thinking of taking it in today to get the exhaust modded... What I want to know is, am I okay just cutting out the resonator, or should I remove the secondary cats as well? Seems everyone who's done it on here has done both. I'm just afraid to get rid of the cats in case it won't pass emissions down the line without them. But if I just take out the resonator, will there be a noticeable sound and/or HP increase? Or must the cats come off in order to get any gains? Also, will taking them off cause any issues? And finally, has anyone taken them off and then passed emissions without any problems?
Would appreciate anyone's input. =) Thanks.
So I have a question, and I'm sorry in advance if its been answered before. I saw several threads pertaining to it, but none of them cleared it up for me. I'm thinking of taking it in today to get the exhaust modded... What I want to know is, am I okay just cutting out the resonator, or should I remove the secondary cats as well? Seems everyone who's done it on here has done both. I'm just afraid to get rid of the cats in case it won't pass emissions down the line without them. But if I just take out the resonator, will there be a noticeable sound and/or HP increase? Or must the cats come off in order to get any gains? Also, will taking them off cause any issues? And finally, has anyone taken them off and then passed emissions without any problems?
Would appreciate anyone's input. =) Thanks.
resonator delete on the C55 is good for sound and will NOT affect emissions. However, there is no power to be gained by deleted this. If you delete the secondary cats, you should see somewhere between a 7-10whp gain and more sound. The secondary cats are NOT monitored by any O2 sensors so there would be any check engine lights (CELs) or any problems. Regarding passing emissions, I suppose it depends on where you live. You should be able to pass a smog test, but if you are in CA and they have visual tests, you MIGHT not pass that. I have read on this forum that an SL55 with deleted resonator, secondary cats, and headers passed emissions in CA...but again, it probably depends on the place you go to. If you aren't in CA, it shouldnt be a problem.
Hope the helps!
The only thing at that point that had me worried was the visual emission inspection in GA. They pulled the mirror out and looked under the car and passed it with no questions asked. I figure since the primaries were still in place they didn't care.
High flow 2nd cats made 10HP/12TQ @ wheels on dyno dynamics dyno (delete makes 13HP/19TQ also @ wheels on DD dyno). Its a great modification to do and is simple & cost effective. If you want a smoother more european tone, go with high flow cats. If you want more of an unrefined muscle car sound then go with 2nd cat delete. There is no real reason to even touch the resonator (especially if you are going to delete 2nd cats, you will want it in place to help smoothen out the tone a bit).
If you plan to do headers, then just do high flow 2nd cats and keep stock resonator in place until the very end. Also remember that any time you do exhaust changes it can take a 2-3 weeks for the full sound transformation to occur (sometimes even longer). If you are going to upgrade sound, you might as well upgrade for power at the same time, just a suggestion...
Hope that helps,
~AMS~
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So I have a question, and I'm sorry in advance if its been answered before. I saw several threads pertaining to it, but none of them cleared it up for me. I'm thinking of taking it in today to get the exhaust modded... What I want to know is, am I okay just cutting out the resonator, or should I remove the secondary cats as well? Seems everyone who's done it on here has done both. I'm just afraid to get rid of the cats in case it won't pass emissions down the line without them. But if I just take out the resonator, will there be a noticeable sound and/or HP increase? Or must the cats come off in order to get any gains? Also, will taking them off cause any issues? And finally, has anyone taken them off and then passed emissions without any problems?
Would appreciate anyone's input. =) Thanks.
1) Deleted resonator
http://www.youtube.com/watch?v=3Sw5ZCzExvg
2) Deleted resonator + cats
http://www.youtube.com/watch?v=C1uxDOef3vY
3) kleemann headers + straight pipe + resonator + cats (on the dyno)
http://www.youtube.com/watch?v=MDzTW9ijRA4
The Best of Mercedes & AMG

The video does not justify HOW LOUD the exhaust really is...you can hear my car from about 4 blocks away at WOT.
The best sound combo is headers & high flow cats, keep stock resonator in place & stock muffler. Its the only real streetable combo, if you start deleting resonators and etc the drone and sound can become too much in conjunction w/ headers & cats. Remember its a mercedes, not a mustang (no offense to any mustang owners)... keep it refined
Last edited by AMS Performance; Apr 22, 2010 at 10:32 PM.




