modifying the stock headers?

ZStig · 03-04-2011, 05:14 PM

The stock headers are restrictive because of the cats inside them right? What if someone cut them open and took out all the stuffing? or just gutting them throught the pipe openings?

mfanatic325 · 03-05-2011, 02:19 AM

Technically that might help a bit. But probably not as good a straight-through design with constant diameter piping.
Also, for the amount of work required to gut the cats from the factory headers, you may as well buy aftermarket and install.
Less hassle this way, and you'll still have stock headers to go back to if you ever need

wrh3 · 03-05-2011, 04:46 PM

They won't flow as well as headers and maybe not as well as they did with cats since they were designed with them. Just pick up the cheapest eBay headers you can find and some e36 head studs with OE gaskets and call it a day ;-) Headers and gaskets should be less than $200......

Diokaef · 03-05-2011, 07:40 PM

You can cut the cats off, but just poking a hole in the cats can an most likely will be a bad idea.

mpower03 · 03-05-2011, 09:03 PM

Quote:

Originally Posted by wrh3

They won't flow as well as headers and maybe not as well as they did with cats since they were designed with them. Just pick up the cheapest eBay headers you can find and some e36 head studs with OE gaskets and call it a day ;-) Headers and gaskets should be less than $200......

what he said

Diokaef · 03-14-2011, 01:16 AM

"A gutted cat can actually hurt power as the empty box can cause flow stagnation, which effectively shortens the length of the moving gas column in the exhaust pipe. The empty box can also reduce important flow velocity. This can be felt as loss in bottom-end power."

03-04-2011, 05:14 PM	#1
ZStig instagram 997turbotom 279 Rep 7,377 Posts Drives: Interlagos Z4MR Join Date: Jun 2008 Location: Delray Beach, FL iTrader: (4)	modifying the stock headers? The stock headers are restrictive because of the cats inside them right? What if someone cut them open and took out all the stuffing? or just gutting them throught the pipe openings? __________________
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03-05-2011, 02:19 AM	#2
mfanatic325 ///M-fanatic 193 Rep 3,885 Posts Drives: '01 911 Turbo Join Date: Oct 2007 Location: Cupertino, CA. iTrader: (23)	Technically that might help a bit. But probably not as good a straight-through design with constant diameter piping. Also, for the amount of work required to gut the cats from the factory headers, you may as well buy aftermarket and install. Less hassle this way, and you'll still have stock headers to go back to if you ever need
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03-05-2011, 04:46 PM	#3
wrh3 Car Guy 31 Rep 796 Posts Drives: 2005 MCS, 2013 Corvette 427 Join Date: Aug 2007 Location: ATL, GA iTrader: (10)	They won't flow as well as headers and maybe not as well as they did with cats since they were designed with them. Just pick up the cheapest eBay headers you can find and some e36 head studs with OE gaskets and call it a day ;-) Headers and gaskets should be less than $200...... __________________ Bill- 2005 Mini Cooper S, 2013 Corvette 427 www.billswebspace.com/bmwindex BMW CCA Member # 389948
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03-05-2011, 07:40 PM	#4
Diokaef Engineer 212 Rep 2,122 Posts Drives: M235I 2015, 335i 2011 Join Date: Dec 2009 Location: TAMPA FL iTrader: (17) Garage List 2008 Z4M Coupe [6.33]	You can cut the cats off, but just poking a hole in the cats can an most likely will be a bad idea.
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03-14-2011, 01:16 AM	#6
Diokaef Engineer 212 Rep 2,122 Posts Drives: M235I 2015, 335i 2011 Join Date: Dec 2009 Location: TAMPA FL iTrader: (17) Garage List 2008 Z4M Coupe [6.33]	"A gutted cat can actually hurt power as the empty box can cause flow stagnation, which effectively shortens the length of the moving gas column in the exhaust pipe. The empty box can also reduce important flow velocity. This can be felt as loss in bottom-end power."
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