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RarlyL8 RarlyL8 is offline
Crotchety Old Bastard
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Join Date: Jan 2000
Location: Huntsville, AL
Posts: 14,182
By "none" I mean a Zork Tube. A Zork Tube is not an exhaust system by street car definition.
If you are talking race cars then the theory is extremely simple - an short cone and large ID short exit pipe with minimal bends.

I have done dyno testing using stock muffler (no cat) vs my various mufflers vs the Zork.
On a stockish 292WHP Euro 930 engine you will gain ~15HP by replacing the stock muffler with a Zork. You gain ~12HP by replacing the stock muffler with my muffler - driver's side exit, dual out, passenger's side exit makes no difference. All are 3"ID.

Iterestingly the driver's side vs passenger's side outlet mufflers sound identical. The extra pipe does not quiet it down.

I also have one of those "Boxes with 2 pipes" you mention. That "muffler" sounded absolutely horrific! The box creates a resonance chamber that amplifies the sound. The tailpipe was huge 4"ID.

When you get above 400WHP bigger ID tube and muffler chamber is needed and design becomes more significant. At that point the turbo is pushing a LOT of air and any restriction becomes a noticeable problem.
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
Old 03-05-2009, 08:41 AM
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