What to do for exhaust scavenging on C55?
Thread Starter
Junior Member
Joined: Mar 2015
Posts: 46
Likes: 2
From: Coachella Valley, CA
2006 C55 AMG
What to do for exhaust scavenging on C55?
Hello everyone! So as I posted a few weeks ago, I just had Kleemann headers installed on my C55. The car now has no cats (Primary or Secondary), no resonator, and it has been tuned by Eurocharged. This all sounds awesome right? Well for some reason I feel alot slower now, obviously it is louder and more free flowing but it doesn't even lurch forward like it used to with a simple tap of the gas. It seems I have lost quite a bit of low end torque and I have been told that I could gain it back somehow through exhaust scavenging. What should I do? X pipe where the resonator was and true dual exhaust? I am a bit clueless when it comes to exhaust work. Any help would be appreciated.
Member
Joined: Jan 2009
Posts: 226
Likes: 6
From: Northern CA
CLK55 AMG, SL55 AMG, C55 AMG
You traded low end torque for high end breathing/HP.
Lots of exhaust experts here that hopefully will chime in with more specific answers for you.
Mercedes tunes these exhaust to best match the M113 motor across the power range. When you start altering OEM exhaust flow/scavenging/etc, there are trade offs, both good and bad as you have found out.
In the meantime, there are a number of threads on this topic you might review. Just search this form with a key word like "exhaust" for one suggestion. Good luck.
Lots of exhaust experts here that hopefully will chime in with more specific answers for you.
Mercedes tunes these exhaust to best match the M113 motor across the power range. When you start altering OEM exhaust flow/scavenging/etc, there are trade offs, both good and bad as you have found out.
In the meantime, there are a number of threads on this topic you might review. Just search this form with a key word like "exhaust" for one suggestion. Good luck.
Last edited by Nokiemon; May 28, 2018 at 12:41 PM.
MBWorld Fanatic!
Joined: Mar 2004
Posts: 2,073
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From: North NJ
2002 C32 AMG, 2013 GLK 350/4, 2015 E63S AMG Wagon
Tuning exhaust is black magic. Very few know how to do it right. In your case I would start with a dyno graph along with adding some measurements like AFR and Spark Advance. Only then you will know if it is your new exhaust alone or your new exhaust in combination with other things, that is messing things up.
Senior Member
Joined: Feb 2014
Posts: 268
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From: DFW
2006 C55
I really wish people would forget they ever heard the word "backpressure".
You neither want nor need backpressure for a car to run properly. In a 4 stroke engine the best exhaust is no exhaust past properly designed collectors. If engines wanted backpressure you'd see mufflers on top fuel dragsters.
I've seen situations where cars lose power with heavily modified exhaust. That is due to a lack of tuning. If you want to get that response back I'd suggest giving the car time to run through adaptation. If that doesn't do the trick then you need some tuning on a dyno. I know it isn't cheap but neither is owning a Mercedes.
On occasion I wish I had bought a friend's 5.7 Magnum R/T instead of my C55. It wouldn't handle as well but I'd be WAY ahead on power if the difference in purchase price had been dropped into mods.
You neither want nor need backpressure for a car to run properly. In a 4 stroke engine the best exhaust is no exhaust past properly designed collectors. If engines wanted backpressure you'd see mufflers on top fuel dragsters.
I've seen situations where cars lose power with heavily modified exhaust. That is due to a lack of tuning. If you want to get that response back I'd suggest giving the car time to run through adaptation. If that doesn't do the trick then you need some tuning on a dyno. I know it isn't cheap but neither is owning a Mercedes.
On occasion I wish I had bought a friend's 5.7 Magnum R/T instead of my C55. It wouldn't handle as well but I'd be WAY ahead on power if the difference in purchase price had been dropped into mods.
Last edited by feets; May 28, 2018 at 10:04 AM.
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Joined: May 2015
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From: Miami, FL
2003 CL 600
It's not gonna come back until you move the curve back down with a smaller exhaust. Exhaust/intake flow increases change the placement of the curve relative to the RPM range, so as you shift the efficiency to be better at higher rpms, you are gonna trade off some at lower rpms. Usually a tune can somewhat compensate by increasing timing in the affected areas to help offset, but it will never feel as punchy because it will never make the same torque it used to at part throttle and low RPM.
Senior Member
Joined: Feb 2014
Posts: 268
Likes: 47
From: DFW
2006 C55
It's not gonna come back until you move the curve back down with a smaller exhaust. Exhaust/intake flow increases change the placement of the curve relative to the RPM range, so as you shift the efficiency to be better at higher rpms, you are gonna trade off some at lower rpms. Usually a tune can somewhat compensate by increasing timing in the affected areas to help offset, but it will never feel as punchy because it will never make the same torque it used to at part throttle and low RPM.
Headers generally improve torque due to better scavenging (helping get more exhaust out of the combustion chamber). There are a lot of factors involved such as primary tube diameter, primary length, style of header, collector size, rest of exhaust, etc. A header that is too large by a significant margin will drop a bit of low end torque compared to a properly sized header but should still be well ahead of a stock manifold.
The exhaust pipe diameter will not cripple power unless it is so small it chokes the engine. Too large of a pipe will make more noise but not significantly impact power output on engines as weak as ours. As fun as it is, 360 hp is laughable in the V8 world.
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Senior Member
Joined: Oct 2014
Posts: 254
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From: Oregon
2006 ML350, 2005 C55, 2004 E55
Was your resonator bypassed with a single straight pipe keeping the factory y to the rear mufflers?
Junior Member
Joined: Apr 2017
Posts: 20
Likes: 1
2006 C55 AMG
I currently have true dual exhaust on my c55, i left all the cats, removed the resonator, and put an electric cutout right before the mufflers. I noticed more power up top and less power down low as other members mentioned. Imo worth the trade off.
Super Member
Joined: May 2013
Posts: 522
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2002 C32AMG
It's not gonna come back until you move the curve back down with a smaller exhaust. Exhaust/intake flow increases change the placement of the curve relative to the RPM range, so as you shift the efficiency to be better at higher rpms, you are gonna trade off some at lower rpms. Usually a tune can somewhat compensate by increasing timing in the affected areas to help offset, but it will never feel as punchy because it will never make the same torque it used to at part throttle and low RPM.
When I swapped the front cats for 200 cell units and ditched the back cats/resonator for a 2.5" system I noticed a loss of bottom end tq under light throttle but the mid range was vastly improved. With the C32 having the twin screw all it takes to get that low rpm grunt back is a smaller pulley/tune.
Thread Starter
Junior Member
Joined: Mar 2015
Posts: 46
Likes: 2
From: Coachella Valley, CA
2006 C55 AMG
Thank you guys for all the advice, I feel alot better about the car now. I was dead sure I had ruined the car in some way but as mentioned above the high end power is such an increase that the trade off is worth it and I should be thankful for it. I think I'll do the xpipe and dual exhaust then be done with it.
