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Discussion Starter #1
Has anyone cut open an Eisenmann full race rear muffler ?

I'm curious as to what the design in inside the muffler
 

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I remember seeing pics of this. It might have been on the e39 page. It was not impressive!
 

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Discussion Starter #3
I'm thinking it's 2 perforated straight through tubes with glass packing , can anyone confirm ?
 

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Discussion Starter #4 (Edited)

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Discussion Starter #5 (Edited)
The inner pipes insude the muffler are 50mm diameter

A nice design compromised by noise emission laws , a well made muffler

We will build something similar but with those inner tubes a larger diameter
 

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Not necessarily seeing where the restriction is--the bigger tip opening not lining up with the piping wouldn't matter, and it sort of looks like a straight-through resonator, which is optimal for power. Optimal diameter depends on what the diameter of the B pipe is. If the Eisenmann matches the B-piping diameter then there isn't much point making it bigger.
 

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Discussion Starter #7 (Edited)
The pipe sizes are

Inlet 2.5"

Internal 2"

Outlet 3" at the front of the exhaust tip

Sounds like a restriction to me but done I guess to keep noise levels within sort of legal levels.
 

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Hmm that's strange they wouldn't simply make the internal the same, don't think there'd be any scavenging effect way back there.
 

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Discussion Starter #9 (Edited)
The Eisenmann race internal pipe in the muffler matches the diameter of a standard M5 exhaust system, for a standard M5 system it could be considered to be non restrictive.



For us the Eisenmann race muffler is a problem / restriction as we are experimenting with a 4 inch internal diameter system

So far we've got some good results , an increase in power and torque across almost the entire rpm range.

We've just modified the exhaust again last night , changed the shape of the centre expansion chamber to reduce drumming and it's made the whole system much quieter.

You can have a normal conversation in the car at idle without drumming or booming , it's somewhere between a stock system and a sport system at idle and low rpm now, at high rpm it's loud


 

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Discussion Starter #10
Boot seal air gaps

Something to check if you're getting any booming or drumming with any exhaust system is to make sure that the boot lid seal has no air gaps, it's common to see a 1 or 2cm gap near the boot lock and that will create a lot of noise in the interior as the boot acts like a big sub woofer
 
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