R129 exhaust experiment

[Sp!ke]

Having looked at all the options for aftermarket exhausts and not really getting excited by whats on offer, I thought I'd buy a second hand rear section and open it up and see what could be done to liven it up a little. Given that my SL didnt come with a centre box as standard, the silencing is done on the back box alone.

So my aim is as follows;

1. Retain stock look
2. Improve sound, target being measurably louder without being obnoxiously so whilst retaining a deep tone.
3. Try not to introduce any droning.

The picture that follows is what you see when you open up one of these silencers and remove all the fiberglass packing.

At this point I wont reveal my thoughts on how to proceed as first off, I'm interested in the opinion of you guys as to how you might tackle this. It may well be some bright spark here comes up with something I've not considered.

 

[aka$h]

The obvious one is to enlarge the holes and pack the box again.

 

[Whitey]

weld in a Y piece inside the box ?

 

[Borys]

Did that before,cut the inside silencers out weld back together,add nice Brabus,amg tips
It won't be loud but very deep
Smaller back box louder it gets
Cheapest way to get it sound nicer

 

[Sp!ke]

The obvious one is to enlarge the holes and pack the box again.

The holes are for sound absorbtion... enlarging them will likely make it quieter.

 

[Stratman]

Shorten the two pipes nearest the top of the picture and replace the U-loop, so the gases don't have as many holes to escape into the glass wadding.

 

[Sp!ke]

Shorten the two pipes nearest the top of the picture and replace the U-loop, so the gases don't have as many holes to escape into the glass wadding.

The pipe routing and length has been carefully calculated to reduce resonance and maintain correct back pressure.

If I shorten the pipes that will likely alter the resonance and cause droning.

My theory is that if I replace the perforated pipes with solid ones then back pressure and resonance will be largely unchanged but noise should be less absorbed into the glass fibre packing and hence more volume. I'll start by replacing all 5 perforated pipes for solid ones. If its too loud I can always reopen and drill some new perforations...

 

[jaymanek]

On my SL60 someone stripped it out completely as far as I could see...
IT sounded great until you booted it at which point it would WHOOOOSH instead of growl!

My AMG box has just made it quiet.

I could have given you my old box but i threw it..

 

[Sp!ke]

I fitted the modified back box to the car yesterday and I have to say that I think I've only gone and cracked it.

On tick over the car is as quiet as standard. It has a lovely deep burble at around 2k and at 4k rpm upwards it really howls like a banshee with a gnarly C63 like rasp.

Maintaining the same pipework routing did as I suspected and there's no droning at motorway speed, and no overbearing noise at all until you want it. :bannana:

Here's a short video. (needs decent speakers or headphones)

[YOUTUBE]cmI3MSRjcak[/YOUTUBE]

http://youtu.be/cmI3MSRjcak

 

[BTB 500]

That sounds pretty good

 

[joesoap]

That sounds fantastic a friend has just bought a CLS63 and the rip is similar to his?
I want that sound for my C32? Will having only 6 cylinders kill my chances?

 

[230K]

Sounds brilliant!!:bannana::bannana:

Has she standard cats?
Is that the 119 or 113 engine?

Thanks,

230K

 

[Sp!ke]

113 engine and yes, both sets of cats still present.

 

[Doodle]

Very nice...fear I might get lynched if I cut open the AMG box to do it though.

 

[230K]

Hi

Anyone got a late model SL500 back box that I can have a play with???

Let me know of any available.

Thanks

230k

 

[Willsco]

This sounds great
I moved to an SL500 after 8 years with a Porsche 928 with "Rear Muffler Bypass" (RMB) - and the sound is the only thing I have missed so far
Would be interested in replicating what you have done
Unfortunately I am a bit of a numpty when it comes to mechanical engineering

 

[BTB 500]

Very nice...fear I might get lynched if I cut open the AMG box to do it though.

Yup that's why I went for the partial decat.

The 113 exhaust system doesn't have a centre muffler, IIRC?

 

[230K]

Yup that's why I went for the partial decat.

The 113 exhaust system doesn't have a centre muffler, IIRC?

Yes the 113 engined cars have jus primary and secondary cats and a rear box.

230k

Sent from my GT-I9505 using MBClub UK

 

[Vlad]

Spike.....did you repack it with the fibreglass or leave that out?

 

[Doodle]

Yup that's why I went for the partial decat.

The 113 exhaust system doesn't have a centre muffler, IIRC?

Unfortunately, being a pre-facelift I don't think I have that option. The centre muffler is already gone but there's only a single cat.