Replacing Secondary Cats with Eisenmann Straight Pipes (w/E-Sport Exhaust) - BMW M5 Forum and M6 Forums

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Old 13th June 2007, 22:15   #1
polar993
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Replacing Secondary Cats with Eisenmann Straight Pipes (w/E-Sport Exhaust)

I recently swapped my Eisenmann Sport exhaust with an Eisenmann Race exhaust, but the sound is a bit too much for me (mainly on cold starts because I live in a condo with shared underground parking....I'm sensing that my neighbors are starting to dislike me because the car is so loud when I start it and leave the garage!).

I'm thinking about putting my E-Sport back on and replacing the secondary cats with the Eisenmann Section 1 straight pipes. For now, I would leave the stock resonators (Section 2) in place. From what I understand, replacing Section 1 will provide more sound than replacing Section 2. Hopefully this will give me the perfect sound that I'm looking to achieve, and won't be too loud on a cold start.

Has anyone replaced Section 1 and kept the stock Section 2, with or without an aftermarket exhaust? If so, I would really appreciate your feedback.

I am concerned about losing back-pressure if I remove the secondary cats and replace them with straight pipes (I've heard this is what happens). Can someone please explain the disadvantage of losing back-pressure? What exactly does that mean? Will I actually lose power as well?

Theoretically, if I create a less restrictive path for the exhaust system by removing the cats and replacing them with straight sections of pipe, that should create more free-flow and power, right?

Before I go down this path, I just want to make sure I'm doing the right thing.

I know the more common solution to adding more sound to an exhaust system is adding an x-pipe in place of the resonators, but again, I heard the sound increase from doing that is minimal.

I welcome and would appreciate your input.

Thanks!

Below are the videos of both my E-Sport & E-Race exhausts.....just looking for something in between.

E-Sport
http://www.youtube.com/watch?v=ROXwGcv0M5s

E-Race
http://www.youtube.com/watch?v=24gcF6bMFgI
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Old 13th June 2007, 23:06   #2
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[quote=polar993;1066885]...I'm thinking about putting my E-Sport back on and replacing the secondary cats with the Eisenmann Section 1 straight pipes. For now, I would leave the stock resonators (Section 2) in place. From what I understand, replacing Section 1 will provide more sound than replacing Section 2. Hopefully this will give me the perfect sound that I'm looking to achieve, and won't be too loud on a cold start.

Has anyone replaced Section 1 and kept the stock Section 2, with or without an aftermarket exhaust? If so, I would really appreciate your feedback.

I am concerned about losing back-pressure if I remove the secondary cats and replace them with straight pipes (I've heard this is what happens). Can someone please explain the disadvantage of losing back-pressure? What exactly does that mean? Will I actually lose power as well?

Theoretically, if I create a less restrictive path for the exhaust system by removing the cats and replacing them with straight sections of pipe, that should create more free-flow and power, right?...I know the more common solution to adding more sound to an exhaust system is adding an x-pipe in place of the resonators, but again, I heard the sound increase from doing that is minimal./quote]

Replacing the secondary cats will not give you that much of a sound increase, but it will increase the power yielding better flow. Sure it decreases the backpressure but not too much so. I have replaced on my M6 my 2ndary cats with straight pipe and the sound diff was small to none.

I have also replaced resonators (section 2) on my E39 M5 and it made a huge in sound way better. I had Dinan exhaust on and wanted it louder so adding the SS X-pipe really increased it. If you saw what the resonator looked like you would understand why it decreases sound so much. Even the name speaks to sound restriction. That is my experience anyway.

Here is a video I did comparing before and afters the cat delete. However, the before vid is my wife driving and she did not rev the engine that much or that high. I drove the after delete and revved much higher. Also the exhaust was broken in more for the cat delete. Listen to the sound at startup is the best compare on this vid.

http://www.youtube.com/watch?v=Zv3L5qR0NoI
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Old 14th June 2007, 00:48   #3
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Quote:
Originally Posted by deknight View Post
Replacing the secondary cats will not give you that much of a sound increase, but it will increase the power yielding better flow. Sure it decreases the backpressure but not too much so. I have replaced on my M6 my 2ndary cats with straight pipe and the sound diff was small to none.

I have also replaced resonators (section 2) on my E39 M5 and it made a huge in sound way better. I had Dinan exhaust on and wanted it louder so adding the SS X-pipe really increased it. If you saw what the resonator looked like you would understand why it decreases sound so much. Even the name speaks to sound restriction. That is my experience anyway.

Here is a video I did comparing before and afters the cat delete. However, the before vid is my wife driving and she did not rev the engine that much or that high. I drove the after delete and revved much higher. Also the exhaust was broken in more for the cat delete. Listen to the sound at startup is the best compare on this vid.

http://www.youtube.com/watch?v=Zv3L5qR0NoI
deknight, your M6 sounds great! In addition to the straight pipes, do you ALSO have the Eisenmann x-pipe with your Race exhaust? I realize what you mean by only a marginal difference with and without the straight-pipes/secondary cats, but I do hear the difference.

From what I've read on this board, adding the x-pipe to the E-Race makes a pretty big difference, but adding the x-pipe to the E-Sport will probably not make too much of a difference. The E-Sport is only a little bit louder than the stock mufflers.

BTW - I also like the difference in driving style between you and your wife! Very easy to tell who's got the heavy foot in the family!
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Old 14th June 2007, 01:36   #4
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As far as power gained and lost...From what I've learned on this board you will not have a problem adding an X-pipe and straight through pipes. In fact deleting the primary cats and replacing the secondary cats with high flow race cats will give you a sizable increase.
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Old 14th June 2007, 04:28   #5
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Quote:
Originally Posted by polar993 View Post
deknight, your M6 sounds great! In addition to the straight pipes, do you ALSO have the Eisenmann x-pipe with your Race exhaust? I realize what you mean by only a marginal difference with and without the straight-pipes/secondary cats, but I do hear the difference.

From what I've read on this board, adding the x-pipe to the E-Race makes a pretty big difference, but adding the x-pipe to the E-Sport will probably not make too much of a difference. The E-Sport is only a little bit louder than the stock mufflers.

BTW - I also like the difference in driving style between you and your wife! Very easy to tell who's got the heavy foot in the family!
No I do not have the x-pipe on the M6. Thanks for the props though.
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Old 14th June 2007, 21:57   #6
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Awesome Sound

Deknight, love the sound of your M6 can only hope my M sounds as good as yours when I receive my e-race in a couple of weeks, cant wait. -Noah
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