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RarlyL8 RarlyL8 is offline
Crotchety Old Bastard
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Join Date: Jan 2000
Location: Huntsville, AL
Posts: 14,390
No, that is the illusion. The neck itself is 3"ID, the "cone" is created by the back-cut angle into the muffler. The cross section at that spot is 3.5". This was done purposely to make the best compromise due to the angle/relation of the turbo to the muffler body. The muffler opens up internally into a 5"ID shell with a 3"ID perforated core. The core contains packing material that settles out to the remaining 3/4 distance to tailpipe. The space occupied by the packing material is influenced by the exhaust gas flow resulting in a cavity at the proximal end of the muffler right where the "bend" of the neck occurs.
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8

Last edited by RarlyL8; 06-20-2009 at 02:14 PM..
Old 06-20-2009, 02:11 PM
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