Secondary Cats removed with DYNO!
Thread Starter
Former Vendor of MBWorld
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From: Glendale Arizona
C55,SL55,C63
There has been alot of talk in the past about this car needing back pressure, Some even went as far to say they a Res-delete would make you loose some HP. I would think they would say the same about secondary cats removed. Well I guess this thread debunks that. Its just about the cheapest horsepower as you are going to get. Cut two pipes and weld two pipes and there you have it.
Thread Starter
Former Vendor of MBWorld
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From: Glendale Arizona
C55,SL55,C63
I wouldn't say go to midas. but any custom exhaust shop in the phonebook could do this i would think. Most important you would want someone who can weld good.
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C 55
Signed: Ex garage DIY exhaust hacker......
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From: South of the Border
06 C55
Thread Starter
Former Vendor of MBWorld
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From: Glendale Arizona
C55,SL55,C63
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From: Western Canada
2013 C63 AMG P31, 2014 GMC Sierra (6.2)
Hey hooleyboy,
First of all another good post and something we need more of! 19wtq and 13whp just seems like a lot to me for just removing the secondary cats and I’m just wondering a few things:
- Did you by any chance inspect them to see if they were clogged? I believe there is/was a recall out for the C55 for this sort of thing. If this was the case then I can easily see how removing them could yield 19wtq and 13whp!
- As you alluded to, I can’t help but wonder if some of the gains you realized were in fact mostly due to the Evosport Headers and removing the secondary cats just allowed them to perform to their true potential. I'm wondering if someone doing this to a stock C55 without aftermarket headers/high-flow manifolds would benefit as much?
- Just for clarification you said you “chopped them off and repiped them with a 2008 M5's exhaust” so you did the dyno after adding the M5 exhaust then or before? Did the M5 exhaust free up some HP/TQ??
- I was surprised that “After i installed these wheels I deff seeing a lose of power at the wheels on a dyno. Anyway” especially considering they are 18s. Do you know if they were heavier than your stock C55 rims?? This makes me wonder how much I may have lost going to 19s. Now, the Renntech’s are supposed to be very light but still – it would kind of defeat the purpose of what I’m trying to achieve……..
- Finally, I will be getting headers in the future (I don’t know which ones) and if there are indeed a lot of gains to be had by removing the secondary then I will indeed have to try this….
First of all another good post and something we need more of! 19wtq and 13whp just seems like a lot to me for just removing the secondary cats and I’m just wondering a few things:
- Did you by any chance inspect them to see if they were clogged? I believe there is/was a recall out for the C55 for this sort of thing. If this was the case then I can easily see how removing them could yield 19wtq and 13whp!
- As you alluded to, I can’t help but wonder if some of the gains you realized were in fact mostly due to the Evosport Headers and removing the secondary cats just allowed them to perform to their true potential. I'm wondering if someone doing this to a stock C55 without aftermarket headers/high-flow manifolds would benefit as much?
- Just for clarification you said you “chopped them off and repiped them with a 2008 M5's exhaust” so you did the dyno after adding the M5 exhaust then or before? Did the M5 exhaust free up some HP/TQ??
- I was surprised that “After i installed these wheels I deff seeing a lose of power at the wheels on a dyno. Anyway” especially considering they are 18s. Do you know if they were heavier than your stock C55 rims?? This makes me wonder how much I may have lost going to 19s. Now, the Renntech’s are supposed to be very light but still – it would kind of defeat the purpose of what I’m trying to achieve……..
- Finally, I will be getting headers in the future (I don’t know which ones) and if there are indeed a lot of gains to be had by removing the secondary then I will indeed have to try this….
Last edited by wawy; Oct 4, 2008 at 12:10 PM. Reason: typo
Thread Starter
Former Vendor of MBWorld
Joined: Jan 2007
Posts: 3,193
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From: Glendale Arizona
C55,SL55,C63
Hey hooleyboy,
First of all another good post and something we need more of! 19wtq and 13whp just seems like a lot to me for just removing the secondary cats and I’m just wondering a few things:
- Did you by any chance inspect them to see if they were clogged? I believe there is/was a recall out for the C55 for this sort of thing. If this was the case then I can easily see how removing them could yield 19wtq and 13whp!
- As you alluded to, I can’t help but wonder if some of the gains you realized were in fact mostly due to the Evosport Headers and removing the secondary cats just allowed them to perform to their true potential. I'm wondering if someone doing this to a stock C55 without aftermarket headers/high-flow manifolds would benefit as much?
- Just for clarification you said you “chopped them off and repiped them with a 2008 M5's exhaust” so you did the dyno after adding the M5 exhaust then or before? Did the M5 exhaust free up some HP/TQ??
- I was surprised that “After i installed these wheels I deff seeing a lose of power at the wheels on a dyno. Anyway” especially considering they are 18s. Do you know if they were heavier than your stock C55 rims?? This makes me wonder how much I may have lost going to 19s. Now, the Renntech’s are supposed to be very light but still – it would kind of defeat the purpose of what I’m trying to achieve……..
- Finally, I will be getting headers in the future (I don’t know which ones) and if there are indeed a lot of gains to be had by removing the secondary then I will indeed have to try this….
First of all another good post and something we need more of! 19wtq and 13whp just seems like a lot to me for just removing the secondary cats and I’m just wondering a few things:
- Did you by any chance inspect them to see if they were clogged? I believe there is/was a recall out for the C55 for this sort of thing. If this was the case then I can easily see how removing them could yield 19wtq and 13whp!
- As you alluded to, I can’t help but wonder if some of the gains you realized were in fact mostly due to the Evosport Headers and removing the secondary cats just allowed them to perform to their true potential. I'm wondering if someone doing this to a stock C55 without aftermarket headers/high-flow manifolds would benefit as much?
- Just for clarification you said you “chopped them off and repiped them with a 2008 M5's exhaust” so you did the dyno after adding the M5 exhaust then or before? Did the M5 exhaust free up some HP/TQ??
- I was surprised that “After i installed these wheels I deff seeing a lose of power at the wheels on a dyno. Anyway” especially considering they are 18s. Do you know if they were heavier than your stock C55 rims?? This makes me wonder how much I may have lost going to 19s. Now, the Renntech’s are supposed to be very light but still – it would kind of defeat the purpose of what I’m trying to achieve……..
- Finally, I will be getting headers in the future (I don’t know which ones) and if there are indeed a lot of gains to be had by removing the secondary then I will indeed have to try this….
I kinda think that with the headers it did help with the gains a bit. I would say that with my findings on the dyno, these gains would only be realized if someone had headers. So i think that is a factor to think about.
As for the wheels I went to a 18x9.5 wheel with a 255 tire. I dont know the exact weight but if the drag strip tells me anything, As soon as i put the new wheels on my trap speed at the drag strip went from a 108mph to 103mph. To me thats a sign the rotational mass is greater with the aftermarket wheels. Your monolites even being 19s, are at least 10lbs lighter per wheel than my rims. I know nothing about physics so I cant say what that would mean on a dyno. IMO lighter is better in most cases.
Yes we did dyno before and after chopping the m5's exhaust up. What you're seeing in the dyno is baseline pull then secondary cat delete with m5 stock pipe fitted. 2.5 inch pipe i believe.
Evosport headers are a good way to go IMO. just about the most affordable ones out their. C55 headers are the same as SL55 headers. So if i ever get an Sl55 I taking these headers with me.
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From: AL,IL, GA, CA
CLS, SLK, ETC
I'm at work n my work doesn't have speakers so I can't hear your car sounds.. But I had a friend with an slk55 with cats removed.. His car sounded like a Harley / Cam'd mustang.. which i didn't like it very much... Way too loud imo...
Its crazy that you can gain those whp /wtq though! Thanks for the infor!
Its crazy that you can gain those whp /wtq though! Thanks for the infor!
Thread Starter
Former Vendor of MBWorld
Joined: Jan 2007
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From: Glendale Arizona
C55,SL55,C63
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From: Chester County
2006 C55
Don't have pics, but I have a C55 with true duals and X-Pipe. I would go lay in the driveway to describe where they are chopped but it is freaking puring here in cow town (burbs outside philly). All I know is whatever is up towards the front that has the sensors is still there, everything else is custom back to the stock mufflers and tips.
Sounds nasty.
Sounds nasty.
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From: Seattle, WA
C55
Just got my secondaries removed today. The sound is AWESOME. Even with the res delete it sounds pretty quiet inside but finally I can hear my exhaust scream from the inside. But when you're just driving normally its barely, i mean, barely louder than before. I don't know from my butt dyno if its faster or not; but I do have heavy *** 19" rims weighing me down too.
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From: Watertown, SD
2005 C55 AMG
The only thing holding me back is the fear of highway drone. I am at 2800 rpm at 80 on the freeway. How is the interior noise at that constant rpm?
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AMG
If you get the high flow cats, it will give you most of the gains with almost zero drone. If you do headers & high flow 2nd cats, keep stock exhaust & resonator. It will still give you very nice exhaust note as if you had an aftermarket catback.
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From: Watertown, SD
2005 C55 AMG
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From: Seattle, WA
C55
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From: Tampa, Florida
2005 c55amg, 2000 clk430, 2002 clk55amg, 2008 clk63amg black series
There has been alot of talk in the past about this car needing back pressure, Some even went as far to say they a Res-delete would make you loose some HP. I would think they would say the same about secondary cats removed. Well I guess this thread debunks that. Its just about the cheapest horsepower as you are going to get. Cut two pipes and weld two pipes and there you have it.
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From: Seattle, WA
C55
have him cut off the secondary cats and the resonator with straight pipes. A lot of shops won't do this as its illegal in many areas to mess with emissions though.
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From: Fort lauderdale, Florida
2005 Red C55 AMG and 2009 Harley davidson NIghtster SIlver and black
I just got my secondary cats deleted and wow it soudsn and feels amazing..
I have to say this is the best mod I did to the car that was so cheap.
I will do a video to show how it sounds..
Sounds unbelieveable!
I have to say this is the best mod I did to the car that was so cheap.
I will do a video to show how it sounds..
Sounds unbelieveable!
Thread Starter
Former Vendor of MBWorld
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From: Glendale Arizona
C55,SL55,C63
what ever you do, if you go with a cat delete make sure you keep the stock clamps in their currant location.You are going to want them at some point.
