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Join Date: Feb 2000
Location: Monroe, Louisiana
Posts: 1,340
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Pre muffler or cat by pass ?
What is the difference between a European Pre-muffler
and a cat by pass ? Thanks Chuck |
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07-10-2004, 09:06 PM
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Now in 993 land ...
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I thought they are synonyms. The latter being more politically correct.
George |
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07-10-2004, 09:08 PM
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Bye, Bye.
Join Date: Apr 2003
Location: Planet Earth
Posts: 6,167
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A cat by-pass is a straight pipe, while a pre-muffler is kinda a mini muffler of sorts. The pre-muffler allows for more back pressure, which provides a greater performance increase than a straight pipe.
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07-10-2004, 10:20 PM
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Join Date: Aug 2002
Location: Galivants Ferry, SC
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The real poop is that a cat by pass is simply an aftermarket pipe...and often doesn't contribute to any real hp gains. The pre-muffler is a Porsche part used in Europe for the non-cat cars and has proper internal shape and geometry ( some perforated internal plate baffles too)...that can add hp. If you go this route, you'll likely need to add a 18 x 1.5 mm bung for an O2 sensor.
--Wil
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Wil Ferch 85 Carrera ( gone, but not forgotten ) |
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07-12-2004, 06:09 AM
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Location: Bellevue, WA
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And, you can plug your O2 sensor into the premuf (if you buy the one w/ the bung). It sort of looks like a cat as well (for anyone inspecting).
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1985 Carrera Targa |
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07-12-2004, 06:39 AM
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No premuff will come with a bung as built from the factory. Remember..these were used for Euro cars in lieu of cat and their DME's were never set up to receive O2 sensor signals.
If you buy a real Porsche pre muff...you need to have the O2 bung added...if you run one. ---Wil
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Wil Ferch 85 Carrera ( gone, but not forgotten ) |
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07-12-2004, 06:47 AM
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Location: Bellevue, WA
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I bought a Dansk euro pre muff. They are an OEM supplier to Porsche for these things of course, but this was not a Porsche part.
You can order them with or without the O2 bung... I went for the bung. I guess they make this model for the US market?
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1985 Carrera Targa |
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07-13-2004, 10:03 PM
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Location: Bellevue, WA
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Here's a pic...
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1985 Carrera Targa |
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07-13-2004, 10:07 PM
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Bye, Bye.
Join Date: Apr 2003
Location: Planet Earth
Posts: 6,167
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Purdy! Here is mine before install with O2 Bung from factory (aftermarket):
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07-13-2004, 10:41 PM
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If you pair it with a sports muffler (dual out) you enjoy gains near pre 74 headers. There are numerous posts about it, with comparison graphs. I have an original pre muff. I had an O2 port welded on. I have yet to get a dual outlet muffler.
Lee 78SC
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78SC coupe, Silver Metallic |
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07-14-2004, 04:09 AM
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I have the same Dansk Premuffler paired with a Dansk 1 in 1 out Sport muffler, very nice package and the sound is good, nice low rumble but not tot loud.
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"Coffee is for Closers" "Push the button Max!!!" |
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07-14-2004, 04:32 AM
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White,
Still running the stock headers then? Dave
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1984 Porsche 911 Carrera 2002 BMW R1150RT 2013 Audi A4 2020 Ford F150 4x4 |
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07-14-2004, 02:35 PM
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Silver 911SC
1987 Porsche 911 Carrera 3.2
