[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.