Rear Muffler (Backbox) Removal - Advice Please

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Hello Everyone,

I am after a bit of general advice please.

I have owned an E85 3.0si for a couple of years now and I really like it. Many memories and much fun. I've become aware of a 'mod' through YouTube (https://www.youtube.com/watch?v=p9DdPu7Jzgg), this involves removing the rear muffler (Backbox) and welding some tubes and tips in its place. I believe it changes the tone and sound of the exhaust for the better (more sound, backfiring plus some droning when cruising at higher revs). My inner hooligan wants this done but my sensible side is on the fence.

I was wondering if anyone has had experience on the following please?

  • How much approximately is this mod to do? - I'm in the UK and I've had a quote for £280 which is a bit spicy for me
  • People who have had this done - have you had to declare it on your insurance and if so what was the cost?
  • Is the mod absolutely obscene or is it good fun (I like sound but I don't want to 'chav' the car)?
  • Have you had any issue getting this through an MOT?
  • Can you actually do this in the UK? - I'm finding it pretty confusing
  • Are there any other alternatives?

Cheers
 
I think it would be worth trying to hear one before you decide - it's defnitely not for everyone as this recent thread illustrates:- https://z4-forum.com/forum/viewtopic.php?f=2&t=125657

I like a bit of volume - my 2nd Coupe had a cat-back custom system and my current one has Powerflow backboxes - but I've heard a 3.0Si with a backbox delete and I would find it annoying pretty quickly!

Maybe something like this might be a good compromise:- https://z4-forum.com/forum/viewtopic.php?f=6&t=83802
 
I had this done a few years ago now. To answer your questions:

- 280 seems steep, personally I wouldn’t want to pay more than 200 for decent looking tips and welded pipework.

- Yes I declared it on my insurance. Not sure what it added on I’m afraid.

- It’s definitely very loud, and there is certainly an argument for it being a bit much especially when going up a long drag, sitting at certain revs with the roof up, cold starts at night etc. When you’re out for a bit of spirited driving it’s great fun though, the snaps and snarls are loud and the engine noise / sound is epic at mid to high revs.

- There shouldn’t be any issues with MOT’s - I’ve had 4 (2 at a bmw dealer) and it’s never been a problem. I don’t think noise is tested for at all and the cats are on the exhaust manifold on our cars so it shouldn’t affect emissions much.

- Yes you can do it in the UK. Do you track the car? I imagine it would fail the stationary test.

- Yea there are alternatives. The best one IMO would be to have a small custom made box put on and piped by a good local exhaust specialist. This way you can explain what you want and have a better chance of achieving it than ordering a cat back system / box online and hoping for the best and it would be a hell of a lot cheaper.

Long story short in my case it’s been great fun for a few years, and as I use the car for pleasure only have been able to get away with it but I’m going to get a small box put on because it’s just a bit too unrefined around town.
 
Thanks for the input everyone, it’s much appreciated.

I use the car mainly for pleasure, but I do take it to work occasionally when the weather is fine.

I think I might be stepping down, off the fence onto the ‘back box delete is to much’ side. I like the idea of the alternatives (Powerflow, and custom). I’ve had a look and there are a couple of independent exhaust shops up in the ‘North’.

Any recommendations of what to ask for and to expect in terms of price please?

Cheers.
 
I currently have a backbox delete and don't feel like it is to my taste (though it does sound amazing, just a little too much for me). I'm heading for a new system on it in a few weeks time, so can share some videos of before (backbox delete) and after.
 
I had mine removed from my 2004 and I love it. Not too loud or appreciative droning at highway speeds. Now the car sounds like it looks! I live in Georgia in US where everyone has modified exhaust systems!
 
I have had the custom system installed and got a before and after recording: https://www.dropbox.com/s/pctymjincmwo1jd/Exhaust%20sound.mov?dl=0

I’m so pleased I made the change, the only thing I miss are the backfires from the backbox delete, but with that said the car is so much nicer to drive without the horrid drone it used to have.
 
This is my 2.5l e85, Backbox mod, i personally don't think its obnoxious in any way if you compare it to you're local chavs with pops and bangs and decats...im 28 and that stuff does my head in now days, just not needed LOL, getting old! :lol:

Here is a little snip of mine, hope it gives some sort of impression.

https://www.youtube.com/watch?v=GwOazHS7AFw&feature=youtu.be
 
Thank you all for taking the time reply to my post. I’ve found the information, especially the videos, really useful.

I’m heading to a local exhaust fabricators (part of the Powerflow franchise) tomorrow morning to have a chat about a custom stainless steel back box made.

I think this would be the best choice to suit my needs. I was quoted £350 over the phone, this seems fair considering the price of off the shelf systems and labour.

I’ll get back to you with an update (and sound if I go ahead).

Just got to persuade the misus now...

Thanks.
 
Thanks for the additional information.

I’ve booked in to have a custom stainless steel back box configured by a Powerflow exhaust specialist

Cheers!
 
Mr Tidy said:
I think it would be worth trying to hear one before you decide - it's defnitely not for everyone as this recent thread illustrates:- https://z4-forum.com/forum/viewtopic.php?f=2&t=125657

I like a bit of volume - my 2nd Coupe had a cat-back custom system and my current one has Powerflow backboxes - but I've heard a 3.0Si with a backbox delete and I would find it annoying pretty quickly!

Maybe something like this might be a good compromise:- https://z4-forum.com/forum/viewtopic.php?f=6&t=83802
Click to expand...

@Mr Tidy - how did you configure your backboxes in terms of sound and could you tell me if there is any excessive drone please?
 
I thought I’d follow up on this post.

I have had the work done by Powerflow, I had two small boxes put on with new tips for £350. I asked for the car to be about 30% louder than stock without too much drone.

I’m pleased with the results, the car is definitely louder and more dramatic, but it’s not over the top which I feared it may be. The backfire is slightly muted when lifting off the accelerator, however it’s more pronounced than stock but it’s not there all the time.

There is some more drone at 4000-6000 rpm but it’s not excessive and is not defining.

I’ll try to get a video together if anyone would find it useful. Overall I’m happy with it and would recommend.

Cheers for the input from everyone it helped me choose.

Strav
 
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