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E36/7 Z3 (1996-2002)
E36/7 Z3 Roadster, Z3 coupe, Z3 M Roadster and Z3 M Coupe talk with our gurus here.

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Old 08-15-2005, 10:45 AM
TurnAround TurnAround is offline
Location: Oregon
Join Date: Jan 2004
Posts: 358
Mein Auto: Z3C, Z3R, X5
I have a dumb question about removing the catalytic converter..

At some point in my Coupe's life I might do some kind of exhaust mod. To get more growel. I heard a 3.0i Coupe at DFest that obviously had some kind of mod.. but I didn't have a chance to talk to the guy. But I take from this.. that there must be some after market options for the 3.0i.

But here's the real question; I was considering the mod only for sound, as I have read that an aftermarket exhaust provides very little HP gain. But then it ocurred to me... our city has no air pollution auto check stations. No regulations at all, and no one to follow up on your car's setup. Portland does, but none of the other towns in OR have a DEQ station. We will likely NEVER get one either.

Soooo.... can I remove my catalytic converter? If I did that, as part of a custom exhaust mod, then wouldn't this provide quite a bit extra HP?

My guess at this is that I can't just do this because the engine's electronics will freak out.. looking for feedback from sensors mounted near the converter. Yes??

Also, would it effect the life of the engine at all? If this were a late 70's to early 80's car, I wouldn't hesitate.. as there are no electronics relying on the presence of the converter. But my impression is that modern cars have highly integrated pollution control systems that constantly feedback info to the engine for fuel and air ratio changes.

My other dumb question; Why do they call some aftermarket exhaust systems "Catback". Is this a play on words. Marketing language that suggests that, "hey, with our muffler, we'll give you some of the power back that your catalytic converter is stealing from you!", and it really has nothing directly to do with the converter? Or, do these systems actually replace the catalytic converter or modify it somehow?

Thanks guys.

'02 Z3 Coupe 3.0i [Hellröt II - Walnuß]
'03 X5 3.0i [GrauGrün - Beige]
'01 Z3 Roadster 3.0i [AlpenWeiß - TraumRöt]
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Old 08-15-2005, 11:50 AM
QikSilver's Avatar
QikSilver QikSilver is offline
Too much is never enough
Location: Ft Lauderdale, FL
Join Date: May 2003
Posts: 266
Mein Auto: 01 M roadster
"Catback", it means from the catalytic converter to the tailpipe.

You might want to avoid removing the cats. You won't pick up that much, and even if your state has no emissions inspection, you could be pulled over and issued a ticket: I can smell a missing cat a quarter mile away, so can the police. A fast car that's emissions legal is much cooler than one that isn't.

01 M roadster, F: GC/Koni short coilover struts, Eibach, Wilwood front brakes, GC tubular swaybar. R: TC Kline springs, short Bilsteins, IE sub & swingarm bushings & shock mounts, 3.23 gear, Rogue dual-ear cover, Eisenmann 4x83 pipes. MISC: Sport mode, Rogue pulleys, keyless, RG Motorsport intake, OZ Superleggera 18" 3 piece.
06 Hemi Durango
04 G35 Coupe
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89 Reynard F2000
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Old 08-15-2005, 12:07 PM
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LmtdSlip LmtdSlip is offline
Do the interns get Glocks
Location: The Sunshine City
Join Date: May 2003
Posts: 9,324
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Mein Auto: 325iC
The federal Clean Air Act [203 (a) (3) (A) and (B)] does
not allow anyone to replace a catalytic converter with
“replacement pipes”. Improper removal or installation of
a catalytic converter by any individual could result in stiff
fines and/or imprisonment.

The only time when removal of a catalytic converter is
allowed is when the vehicle is being shipped to a country
that does not sell unleaded gasoline. The vehicle owner
must have a letter from the EPA authorizing the catalytic
converter’s removal. Vehicles sent to Canada or Mexico
are not eligible for this exemption.

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