Catless X-pipe drone

[aswy6]

Hello everyone,
Just wanted to get an opinion from you catless guys with stock rear section. So here is my story: I decided to pull the trigger and put my full catless x-pipe on my car. The exhaust is made by bimmerworld and it's their first prototype so the actual X section is not as far forward but essentially it's the same deal (just 5hp less in mid range and same at the top). Anyway, the exhaust is in 3 pieces (2 front pipes eliminating primary cats and third piece is the X section). I have connected them using a clamp that is 2.5" outer diameter on one side and 2.5" diameter on the other side to accommodate the change in size of the pipe as one of the pieces inserts into another. After I got all of it installed, it sounds awesome and no codes however (drove about 70 miles already). The only thing is that I get a very nasty "buzzing" sound like metal to metal sound and it comes right at 2k rpm and stays until 2.5k and then goes away. This sound only comes when car is under load and if I just sit still and rev the engine up to 2-2.5k the sound can not be heard. What I think could be happening is a leak at the headers because I just used the impact gun to tighten the Torx bolt at the headers and did not hold the bolt behind it.
After all of this information I want to ask you guys if you think it's a leak at the headers or the clamp could be making this funky noise because it's different size and may be needs readjustment to properly seal everything? Or could it be something else? Thanks everyone

[Cbozz]

I ran OEM exhaust with catless setup and there is no drone with OEM exhaust.
You do need to hold the back nuts when you tighten the bolts otherwise those will spin... there is your problem. You should go over every bolt in your setup and make sure it's tight and jack up the car while running it and maybe someone revving it and see if you have any leaks... just feel it with your hand or if you can hear it... besides drone is not metal on metal but it sounds like woofing bass! Cabin bass that will rattle your change in the center console... good luck

[aswy6]

Originally Posted by Cbozz

I ran OEM exhaust with catless setup and there is no drone with OEM exhaust.
You do need to hold the back nuts when you tighten the bolts otherwise those will spin... there is your problem. You should go over every bolt in your setup and make sure it's tight and jack up the car while running it and maybe someone revving it and see if you have any leaks... just feel it with your hand or if you can hear it... besides drone is not metal on metal but it sounds like woofing bass! Cabin bass that will rattle your change in the center console... good luck

It does not sound like Woosh. It sounds like metal to metal contact like you put some coins into metal can (not exactly but reminds it). I will try to tighten headers first and then report back because it kind of feels like it's below my feet but there is no vibration coming through the car or center console just that drone at 2k

[aswy6]

May be not so much drone rather than buzzing

[Ngilbe36]

Get your car back on a lift and see if you have a leak anywhere (black marks will tell you where). Also make sure all of the clamps are seated properly and the bolts are tight. If its not that, there may be a bad weld somewhere or bad clearance to something on the car.

I am fully cat-less as well. Initially I had the modded OEM rear section and had to change it back to stock, too much rasp.
I love it now though.
Good luck with the troubleshooting.

[aswy6]

Today I have adjusted headers again and everything is super tight there. Also made sure that exhaust is not touching the bottom of the car but the sound is still there. Here is what it sounds like.
https://www.dropbox.com/s/ankks6ko3v...%20AM.mov?dl=0
https://www.dropbox.com/s/3hatztkxxg...%20AM.mov?dl=0

[Properstyle]

sounds like an exhust leak that is rattling the heat shield or you have what happen to me. I actually cracked one of the plates in side the factory muffler. I had to re open the muffler and have it tack welded.

[aswy6]

Originally Posted by Properstyle

sounds like an exhust leak that is rattling the heat shield or you have what happen to me. I actually cracked one of the plates in side the factory muffler. I had to re open the muffler and have it tack welded.

Are you talking about the rear clamp that seals the x-pipe to muffler? Also note that the sound is not there when I am standing still and revving the engine. It only comes when the car is under load. Feel like it comes right when vanos kicks in

[JustAnothaM4]

I also have the BW x-pipe without cats or res and it has that same buzz between 2-2.5k rpm...Mine sounds a lot louder with the Dinan Mufflers. I attributed the sound to not having resonators.


Not the best video displaying the sound.

[aswy6]

Originally Posted by project e46m3

I also have the BW x-pipe without cats or res and it has that same buzz between 2-2.5k rpm...Mine sounds a lot louder with the Dinan Mufflers. I attributed the sound to not having resonators.


Not the best video displaying the sound.

The outside my car sounds awesome but the inside buzz is definitely there. Mine has 2 resonators however

[roastbeef]

sometimes catless xpipes just have a metallic ringing or buzzing sound.