z4m Exhaust modification

pixelloft · Post by **pixelloft** » Sat Mar 17, 2012 6:16 pm

I thought some of the z4m owners may find this interesting. Some of you know i have recently fitted 2 z4m back-boxes to my 3.0si. I thought i would share some pics. I wasn't very happy with the sound after all this work and was trying to find a way which would give me a little more noise without droning but that didn't cost the earth (i.e replacement backboxes). Well I found some forums where porsche owners were putting in backbox bypass pipes to add a little more fruitiness and thought, what the hell. I went to a stainless steel fabricator and had 2 3/4" stainless pipes bent to my spec and went back to kustom 101 who kindly obliged with the drilling and welding of the bypass pipes. I'm really happy with the results... no droning, a really fruty exhaust note when revved. All i have to do now is put an x pipe in the center of the exhaust to remove the put put put put noise on tick-over. Here is a clip with sound:

http://www.pixelloft.com/z4/exhaust.mov

Beedub · Post by **Beedub** » Sat Mar 17, 2012 6:28 pm

that sounds great

pixelloft · Post by **pixelloft** » Sat Mar 17, 2012 6:31 pm

Thanks Bryon,

Well couldn't have done it without you shiny old backboxes!

I'm glad it's sounding better now... just need to sort the pitta patter i'm getting because of no x pipe.

Bumpy · Post by **Bumpy** » Sat Mar 17, 2012 7:17 pm

Better to say you "Went Undercover" to discover this Porsche technology...
Or better yet ...Just say you sourced this idea from an undisclosed location.

Seems like a good and reasonable fix.
For some reason Im still having problems with a muffler that costs over a grand USD ...
Anyone ever try an extended length 3/4 inch drill bit rammed up the exhaust pipe ?
Worked on my Harley..

Incompatible · Post by **Incompatible** » Sun Mar 18, 2012 3:29 am

I wonder how this would work on a standard Si back box? Pixelloft, any thoughts? Maybe a tube for each inlet?

M@r]{ · Post by **M@r]{** » Sun Mar 18, 2012 10:12 am

Really like this. Do you think this is something one of those custom exhaust manufacturers like Topgear could do?

pixelloft · Post by **pixelloft** » Sun Mar 18, 2012 10:25 am

I wonder how this would work on a standard Si back box? Pixelloft, any thoughts? Maybe a tube for each inlet?

Yes, this would work no problem. The porsche guys use 1". If i were to do it again i would be braver and go with 1" but 3/4" is still good.

Really like this. Do you think this is something one of those custom exhaust manufacturers like Topgear could do?

Most exhaust guys can't bend 1" or smaller stainless. You would probably need to get the tube made up by someone else and then taken to your exhaust place to be welded up. I would probably just find your local stainless steel fabricator and get them to bend and weld the steel up... if you take some pics and take the exhaust off the car, most friendly companies would do this i'm sure.

I used these guys in tewkesbury to bend the tube:

http://www.warren-engineering.co.uk/

I'm sure if you ring them with the dimensions, they would do it for others.

ranski · Post by **ranski** » Sun Mar 18, 2012 10:29 am

Excellent mod!

Sent from my iPhone using Tapatalk

sammyz · Post by **sammyz** » Sun Mar 18, 2012 8:35 pm

Cool mod, very interesting alternative to fitting new boxes to a Z4M.

M@r]{ · Post by **M@r]{** » Mon Mar 19, 2012 2:34 pm

Have you got the measurements etc that you went to that Warren Engineering place with? Saves me having to remove my exhausts and somehow get to the steel fabricators

Paza3 · Post by **Paza3** » Mon Mar 19, 2012 2:50 pm

I like that will give it a go maybe tewkesbury is only up the road form me, Can ask you how much were the pipes to get made up , also who fitted them and the cost as well please

if you would rather not say I can pm,

I have an Si so thinking 2 pipes each tail pipe , just a little extra raspe 1" I think maybe a Y shape to each pipe maybe.

Thanks for sharing could be a nice little soloution

Edit : kustom 101 ! they did my 350 bumper last year great guys, I thought they only did bodywork?

Aliv6 · Post by **Aliv6** » Mon Mar 19, 2012 4:02 pm

How bizarre!

Incompatible · Post by **Incompatible** » Mon Mar 19, 2012 8:19 pm

Paza3 wrote:I like that will give it a go maybe tewkesbury is only up the road form me, Can ask you how much were the pipes to get made up , also who fitted them and the cost as well please if you would rather not say I can pm,

I have an Si so thinking 2 pipes each tail pipe , just a little extra raspe 1" I think maybe a Y shape to each pipe maybe.

Thanks for sharing could be a nice little soloution

Edit : kustom 101 ! they did my 350 bumper last year great guys, I thought they only did bodywork?

Paza3, I'm very interested in this mod. Let us know how it works out with pics if you can.

Paza3 · Post by **Paza3** » Mon Mar 19, 2012 8:51 pm

Will do mate , both places are local to me maybe 30 mins drive cannot cost that much??? bit of pipe hours labour ??

I do some videos and stuff as well

pixelloft · Post by **pixelloft** » Mon Mar 19, 2012 10:12 pm

Hi Patrick,

PM replied to, but for all interested, pipes were £20 (but the machine was set up and ready to go on another big job they had with the right radius and diameter tube) and fitting was about £45 (but i took the backboxes off for them so no messing around with ramps.

After living with it for a few days, i'd recommend the 3/4" pipe... i think 1" may be too much. Don't bother with a y pipe... just go with 2 x 3/4" pipes or if you want less effect, go with 1 3/4" pipe because you have the equivalent of an h pipe on the si anyway so there shouldn't be a problem with unbalancing anything by just having one bypass pipe on one of the exhausts.

There is absolutely no droning or noticeable exhaust note change when cruising.
There is quite a bit of spitting and popping on overrun (and only on overrun) which i love but some may not.

I have driven a lot of cars with a lot of really nice exhaust systems, but this is just superb... very raspy and sporty on acceleration... fun popping and spitting on overrun, a lovely rumble on tick-over and no droning whatsoever.

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