Question: Removing Secondary Cats (possible issues)
04-27-2009, 03:11 AM
#1
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Question: Removing Secondary Cats (possible issues)
So I had planned on taking my car to my exhaust guy Tuesday to remove the secondary cats, along with gutting the baffles and such in the mufflers.
I was talking to a friend of mine, who worked for MB & is extremely knowledgeable, and he told me it may not be a good idea. He said that the computer would think the engine was running cold and in turn I would run lean and possible throw a check engine light.
To my knowledge there are only sensors on the primary cats so I’m unsure how it would run any differently with the secondary removed and the mufflers gutted. I would only expect a slight increase in flow and hopefully a noticeable increase in sound (main reason for even doing anything)
Input anyone?
I was talking to a friend of mine, who worked for MB & is extremely knowledgeable, and he told me it may not be a good idea. He said that the computer would think the engine was running cold and in turn I would run lean and possible throw a check engine light.
To my knowledge there are only sensors on the primary cats so I’m unsure how it would run any differently with the secondary removed and the mufflers gutted. I would only expect a slight increase in flow and hopefully a noticeable increase in sound (main reason for even doing anything)
Input anyone?
04-27-2009, 04:32 AM
#2
So I had planned on taking my car to my exhaust guy Tuesday to remove the secondary cats, along with gutting the baffles and such in the mufflers.
I was talking to a friend of mine, who worked for MB & is extremely knowledgeable, and he told me it may not be a good idea. He said that the computer would think the engine was running cold and in turn I would run lean and possible throw a check engine light.
To my knowledge there are only sensors on the primary cats so I’m unsure how it would run any differently with the secondary removed and the mufflers gutted. I would only expect a slight increase in flow and hopefully a noticeable increase in sound (main reason for even doing anything)
Input anyone?
I was talking to a friend of mine, who worked for MB & is extremely knowledgeable, and he told me it may not be a good idea. He said that the computer would think the engine was running cold and in turn I would run lean and possible throw a check engine light.
To my knowledge there are only sensors on the primary cats so I’m unsure how it would run any differently with the secondary removed and the mufflers gutted. I would only expect a slight increase in flow and hopefully a noticeable increase in sound (main reason for even doing anything)
Input anyone?
04-27-2009, 04:49 AM
#3
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C55,SL55,C63
I did see a gain in chopping out my secondary cats. I would leave the stock mufflers just the way they are. I think that sound amazing. Get rid of the res and 2nd cats and you will have a sound you will love. search You Tube under my user name Hooleyboy. I got races and sound clips you can check out.
04-27-2009, 10:21 AM
#4
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You can dump the second cats-they serve no real purpose (emissions only)-the front bank are the ones that you need to get tuned out (remove the O2 sensor read) or have high flows installed-and I agree with Hooley-leave the muffs alone (or try and sell them-someone would like a set of AMG's on their car!)
04-27-2009, 05:01 PM
#5
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2002 C32 Black/Charcoal
You can dump the second cats-they serve no real purpose (emissions only)-the front bank are the ones that you need to get tuned out (remove the O2 sensor read) or have high flows installed-and I agree with Hooley-leave the muffs alone (or try and sell them-someone would like a set of AMG's on their car!)
Better sound, lose 20 lbs (res and secondaries), better performance, no smog issues. The only downside is the cost of removal, IMO.
04-27-2009, 05:15 PM
#6
I removed the 4 cats, i installed custom muffles instead, it throws sometimes check engine light but all i can say that i use to race with a friend always door to door, after the 4 cats removed i put now 3 cars on him plus the sound very owesome and high.
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04-27-2009, 06:24 PM
#8
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Actually, they do not even really serve any emissions purpose either, unless perhaps if your primaries were to stop doing their job. A good friend of mine had his track car (no resonators, no secondaries) smog tested and it passed California standards easily. The sound without secondaries/resonator is much better, IMO, and the car definitely feels faster.
Better sound, lose 20 lbs (res and secondaries), better performance, no smog issues. The only downside is the cost of removal, IMO.
Better sound, lose 20 lbs (res and secondaries), better performance, no smog issues. The only downside is the cost of removal, IMO.
04-28-2009, 07:28 PM
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05-01-2009, 10:50 AM
#14
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Its a common fix for CEL on O2's-buy 1-2 spark plug spacers (if you need 2-drill out the first one to the correct dia for the sensor) and use that in the bung to "push" the sensor out of the exhaust flow (it makes the ECU think there is resistance on the exhaust if it isnt getting the full stream on the O2 sensor tip)-
05-01-2009, 12:09 PM
#16
Super Member
Nope-these are the second set of O2's we are tricking-not the fronts-the fronts monitor the AFR's-the rears....I dont know what those do on any car....really-anyone know? They're always narrow band....
05-01-2009, 01:55 PM
#19
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05-01-2009, 03:38 PM
#20
C32s have definitely removed the secondary cats before. however, you will not see sizable gains like Hooleyboy did. You will have a slightly louder exhaust sound, will drop a little bit of weight, and will have a little better flowing exhaust. maybe a gain of 1-2whp, like with the resonator delete. however, if you ever did headers, deleting the resonator and secondary cats will net you more gains with the headers than if you had the resonator and secondary cats b/c these are no longer bottlenecks in the exhaust.
05-01-2009, 07:30 PM
#21
MBWorld Fanatic!
deleting secondaries? not it 1000000% does not throw any codes. O2s are not over there. they are up front by the primaries.
C32s have definitely removed the secondary cats before. however, you will not see sizable gains like Hooleyboy did. You will have a slightly louder exhaust sound, will drop a little bit of weight, and will have a little better flowing exhaust. maybe a gain of 1-2whp, like with the resonator delete. however, if you ever did headers, deleting the resonator and secondary cats will net you more gains with the headers than if you had the resonator and secondary cats b/c these are no longer bottlenecks in the exhaust.
C32s have definitely removed the secondary cats before. however, you will not see sizable gains like Hooleyboy did. You will have a slightly louder exhaust sound, will drop a little bit of weight, and will have a little better flowing exhaust. maybe a gain of 1-2whp, like with the resonator delete. however, if you ever did headers, deleting the resonator and secondary cats will net you more gains with the headers than if you had the resonator and secondary cats b/c these are no longer bottlenecks in the exhaust.
Cool, thanks brother. Hope you're feeling better.
03-31-2011, 02:56 PM
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86 16v turbo, 02 c32
Its a common fix for CEL on O2's-buy 1-2 spark plug spacers (if you need 2-drill out the first one to the correct dia for the sensor) and use that in the bung to "push" the sensor out of the exhaust flow (it makes the ECU think there is resistance on the exhaust if it isnt getting the full stream on the O2 sensor tip)-
03-31-2011, 09:48 PM
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86 16v turbo, 02 c32
03-31-2011, 10:24 PM
#25
You will have no problems. Although it is preferred to put in an X-pipe instead of just running two parallel straight pipes. It will improve scavenging effects and also help "clean up" the exhaust note quite a bit. You should pick up some low end part throttle torque, and high end HP WOT, but it won't really do anything in the mid range (maybe 1HP).
hope that helps.
AMS
hope that helps.
AMS
