Backbox deleting a 2.5 auto?

[skmattwell]

Is backbox deleting a 2.5 auto e85 worth it? Given the 2.5 doesn't have the sound generator as standard, I'm left wanting a bit more noise. However given it has a 5 speed gearbox, I imagine the motorway drone would be even worse than a 3.0 as it will be revving higher?

Eager to hear everyone's thoughts, not sure of the differences in sound between the 2.5 vs 3.0

 

[Smartbear]

Drone is more pronounced at lower rpm, don’t know if you’re aware but it’s possible to retrofit the sound generator.
Rob

 

[skmattwell]

Ah interesting, I thought it was the other way round and it would be more annoying at higher rpm.

I have also thought about the sound generator mod and it's roughly the same price as a backbox delete. Wondering which one, if any, to go for really.

 

[mr.tourette]

Better getting a custom backbox or a modified standard box for better sound with less drone

 

[zriha]

The previous owner of my 2.5i E85 retrofitted the sound generator (at the official BMW dealership), and it gives a crazy sound, even with the stock exhaust, so maybe you can retrofit it.

 

[enuff_zed]

The previous owner of my 2.5i E85 retrofitted the sound generator (at the official BMW dealership), and it gives a crazy sound, even with the stock exhaust, so maybe you can retrofit it.

You can. Very easily. It costs a bit to get all the parts together though.
Wifey wanted a backbox delete but luckily common sense and forum advice prevailed. The sound generator does the job for her.

 

[skmattwell]

Sounds like the sound generator mod is the way to go. Looks to be around £170 all told... maybe next month :rofl:

 

[Jamesbradbury]

I've actually found the sound generator to be not that great. The comments I always had were "do the speakers pump engine noise through the cabin" which I guess is cool but it does sound a bit fake imo. I did my own back box delete and it's completely different. It depends what you want, just a tad more noise then get sound gen. Lots of noise in and out delete the box although if you daily it like I did you'll get used to it and your partner will moan when you do a long drive on the motorway. Best of both worlds is a custom cat back although it will cost more. I personally wouldn't pay for the sound generator but that's just me. I have a 3.0i btw.

 

[enuff_zed]

The sound generator is essentially fake, but it is generated by the induction of air. Only fake bit being that it acts on a kind of resonating drum skin that is 'tuned' by BMW to sound just right. On the E85 it is a mechanical device, it does not use the speakers. It merely amplifies the natural noises and pipes them into the cabin.
To go back to my old-skool Ford days, the sound generator is the modern equivalent of putting a K&N filter on the carburettor, whereas the back box delete is akin to fitting a cherry bomb.
The two sounds are different and a lot depends on whether you want to hear it for yourself or want the whole town to know you just got home. :wink:
Also, with the sound generator, you can make it louder by removing one or both pieces of foam rom the pipe that ducts the sound into the cabin. The sound only really occurs when you put your foot down. Whilst I've never had the back box delete, I have read many times that it can create a constant drone at certain speeds/revs, and there's not much you can do to alleviate that other than change gear or slow down.

 

[skmattwell]

I'm thinking I start with the sound gen and delete the backbox if I'm not happy with it. If you have all the foam in the sound gen, I'm guessing it won't be much noiser than not having it at all right?

 

[enuff_zed]

I'm thinking I start with the sound gen and delete the backbox if I'm not happy with it. If you have all the foam in the sound gen, I'm guessing it won't be much noiser than not having it at all right?

Sorry, can't help you there. Fitted it from scratch and took the bulkhead end foam out at the time.