Garages that do the backbox mod?

[AndyBeech]

Hi guys,

Does anyone know any garages that can do the M backbox mod around the Berkshire area? I'm not sure which of the 'mods' is best but I'm guessing the one that involves removing the stuffing etc. from the box for a bit more rasp and the like, but no drone! Anyone have any ideas would be much appreciated!

Cheers
Andy

 

[DPG]

I quite like the bypass mod. Not sure about removing the gubbings though.

 

[AndyBeech]

I quite like the bypass mod. Not sure about removing the gubbings though.

I'm not sure to be honest which is better, hopefully someone who's had it done can post what the differences are. I just wouldn't mind a little more sound and rasp retaining the original back box sound with no drone.......

 

[Anonymous]

Hiya Woots, it was around £80 iirc, about 1 1/2Hrs work, I have had an MOT since and they're fine

This man is the best person to talk to about this mod. I've been interested in it, but have struggled to find comparison videos. I don't know how to tag members on this forum, so hoping the quote will alert Darren to this thread for more help and info.

 

[jimmybell]

to be honest videos tend not to do either mod justice. The tones you're looking to improve are exactly the tones that both cheap mics (phones/gopros etc) and cheap sound systems (most likely your headphones/speakers) won't replicate.

my custom oem+ mod (internals re-worked):

before https://www.youtube.com/watch?v=2f0HmG8Bcj8
after https://www.youtube.com/watch?v=5m0PB8OcdPs

You can't really tell that much on the video. The hints of the change are there - but in real life it's quite different. much lower burble at idle/startup. deeper sound overall.

 

[Anonymous]

to be honest videos tend not to do either mod justice. The tones you're looking to improve are exactly the tones that both cheap mics (phones/gopros etc) and cheap sound systems (most likely your headphones/speakers) won't replicate.

my custom oem+ mod (internals re-worked):

before https://www.youtube.com/watch?v=2f0HmG8Bcj8
after https://www.youtube.com/watch?v=5m0PB8OcdPs

You can't really tell that much on the video. The hints of the change are there - but in real life it's quite different. much lower burble at idle/startup. deeper sound overall.

An explanation of what your mod is wouldn't go amiss! I can hear it's slightly deeper on idle... Costs and explanation?

 

[ncrossy1980]

I've seen a few other posts regarding this mod, but I can't find them. Something about welding pipes on or around the backbox? I'd love to know exactly what it is too, I'm after an exhaust that pops and crackles but I don't want the ridiculous boy racer/renault clio/vauxhall corsa drone and rasp noises!

 

[BMWZ4MC]

I have an exhaust bipass mod on my S2000 and it sounds fantastic. IIRC, the bipass pipes are around 30mm internal diameter. Amongst the S2000 community the bipass is regarded by many as better than almost all aftermarket back boxes available. For those who are interested, I can point you in the direction of the man who did mine. The bipass mod is much easier on the S2000 than the Zed but I'm sure he would have no problem modifying Zed exhausts too. I think he said his day job is for Jaguar (I've forgotten) but he spends his spare time building rally cars and modifying MX5s, including developing a turbo conversion. He has a workshop with a lift near Silverstone.

 

[BMWZ4MC]

Exdos is the man to ask regarding gutting the back boxes.

 

[jimmybell]

I gave an explanation, the internals were re-worked

Took a set of OEM backboxes, gutted the insides, replaced the internal S bend with a straight through perforated pipe. It's pretty well documented somewhere.. i'll see if i can find the thread tomorrow.

 

[BMWZ4MC]

Search 'exhaust' or 'back box' in Exdos's posts and I'm sure it will appear!

 

[exdos]

Here's a link to one of my postings on the subject: http://www.z4-forum.com/forum/viewtopic.php?f=9&t=52845&p=828531&hilit=OEM+//M+silencer+mod#p828531

Here's a video of me datalogging an acceleration in my Z4MC in 3rd gear from 2000rpm to the redline and you'll hear what it sounds like inside the car (turn your speakers up) with my gutted silencers and RamchargerII mod https://www.youtube.com/watch?v=-ZaDO7NbN_Y&spfreload=10

NOTE that the Magnehelic Pressure Gauge (very accurate) shows that the pressure inside the air-intake system never falls below 0 inches of water (= ambient pressure) although the car is at WOT during the acceleration and starts at a speed where ram-pressure will have little effect. Show me another air-intake system on a normally aspirated car that can achieve that. 8)

 

[Machine monkey]

I am sure Jimmy wont mind but hear are some pictures of the insides of his back boxes. Followed exdos guide and ended up with what you can see below. And you have heard the sound. Its a great mod sound great.