Muffler delete/back box mod

[Dwaynos]

I've been wanting to perform some sort of exhaust mod on my m5 for a while. I came across a pair of cheap rear boxes and decided I would modify the internals.

I cut them open on both sides not just the top, removed the sound deadening, welded up the perforated section on the top and bottom, put all the fluff back in and welded them back up. I wasn't sure if having an empty can would make it resonate, this is why I put the fluff back in.

Sounds so much better, the flaps must be wired open though, without doing this it's pretty quiet. Ideal if you have an exhaust meister or a tune that can control the flaps so you can have a choice.

This is a very cheap mod and I would recommend this to anybody who wants more noise without going the downpipe route.

[NZ-M340ixDrive]

awesome im contemplating this any video clips of sound?
Plus how about doing a resonator delete too?

[Ickdeep]

That's cool, but I just ended up delete the muffler it self and replacing it with the stock resonators that I took out. I also have catless downpipes and it sounds great!

[Dwaynos]

Originally Posted by Benji335i

awesome im contemplating this any video clips of sound?
Plus how about doing a resonator delete too?

I'll see if I can get something over the weekend.

I have also done the resonator delete. I will say I think the car sounds great now. Having the valves there to open and close is great aswell. Despite what people say, I do get drone under 2k rpm which gets annoying when cruising. Closing the valves stops this completely.

I personally don't fancy running catless downpipes although it would sound better. Anyone on a budget should definitely look into the back box mod and resonator delete, be sure to keep valve functionality though. I have another thread showing my way of fitting a switch to allow valve control without spending money, check that out also.

[NZ-M340ixDrive]

Originally Posted by Dwaynos

I'll see if I can get something over the weekend.

I have also done the resonator delete. I will say I think the car sounds great now. Having the valves there to open and close is great aswell. Despite what people say, I do get drone under 2k rpm which gets annoying when cruising. Closing the valves stops this completely.

I personally don't fancy running catless downpipes although it would sound better. Anyone on a budget should definitely look into the back box mod and resonator delete, be sure to keep valve functionality though. I have another thread showing my way of fitting a switch to allow valve control without spending money, check that out also.

Nice!
Apologies just seen this, could you send that link so I can see how you had control of the valve?
Currently I’m stock with a tune does putting it in sport plus open the valve...?
Was it easy to weld the perforated section?

Thanks again

[Dwaynos]

Originally Posted by Benji335i

Nice!
Apologies just seen this, could you send that link so I can see how you had control of the valve?
Currently I’m stock with a tune does putting it in sport plus open the valve...?
Was it easy to weld the perforated section?

Thanks again

https://f10.m5post.com/forums/showthread.php?t=1618056

Sport plus may open the valves, it depends if this has been assigned by the tuner. I noticed that sport plus can open the valves on factory tune but does what it wants most of the time.

Welding the perforated sections isn't a hard job, some stainless steel sheet cut to size does the job.

[NZ-M340ixDrive]

Originally Posted by Dwaynos

https://f10.m5post.com/forums/showthread.php?t=1618056

Sport plus may open the valves, it depends if this has been assigned by the tuner. I noticed that sport plus can open the valves on factory tune but does what it wants most of the time.

Welding the perforated sections isn't a hard job, some stainless steel sheet cut to size does the job.

Nice one! I’m not that mechanically minded so I will not be able to do that at all.

Hopefully I will be able to code the valve option in with the tune so it stays open. My tuner is just finding out about that from dimsport.

My tune just has speed limiter removal for now.

I do want to do the muffler/back box mod the only thing putting me off is cutting into my stock exhaust

[Dwaynos]

Originally Posted by Benji335i

Nice one! I’m not that mechanically minded so I will not be able to do that at all.

Hopefully I will be able to code the valve option in with the tune so it stays open. My tuner is just finding out about that from dimsport.

My tune just has speed limiter removal for now.

I do want to do the muffler/back box mod the only thing putting me off is cutting into my stock exhaust

Believe me it's well worth it, remove the resonators aswell whilst you're at it. It's cool having the valves to open and close when you want. This is especially useful when you want a quiet startup. Definitely find out about cold start removal aswell.