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7 Series - E38 (1995 - 2001)

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  #1  
Old 03-21-2013, 08:50 AM
Celthorseman Celthorseman is offline
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Location: La Grange, CA
 
Join Date: May 2012
Posts: 16
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Mein Auto: 740i
To cat or not to cat

Ok here is what I am wondering. I have a 98 740i and last year some time I had to change out one of the cats. Well it is starting to have the same problem that it had last year so I am thinking the other cat needs to be changed out. Being I am a little on the poor side right now I was thinking of just cutting them out and putting test pipe in. I am just not sure if that will mess anything up with the way that it runs (i.e. the O2 sensors.) I don't have to worry about smog where I live so no worries there.

Any thoughts from the peeps out there?

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  #2  
Old 03-26-2013, 04:32 PM
skinchin13 skinchin13 is offline
SittinRock
Location: Landrum, South Carolina
 
Join Date: Apr 2011
Posts: 61
Mein Auto: 1996 BMW 750il
When I had my 750il. I cut the cats and sold them to a company on the internet. I got some where around 280 for the stock ones. Then i just had a shop weld in pipe. It will cause the check engine light to come on but the car should run fine. Mine never skipped beat
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  #3  
Old 04-03-2013, 02:54 AM
mrcchevy25 mrcchevy25 is offline
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Location: Virginia
 
Join Date: Apr 2013
Posts: 1
Mein Auto: 740il
I have a 1999 740il. I had the cats cut and haven't had any problems. A little more power not being restricted by the cats. Gas ml is the same. So I say run free.
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  #4  
Old 04-03-2013, 08:30 PM
JasonSC540ia JasonSC540ia is offline
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Location: Alamogetto NM
 
Join Date: Aug 2009
Posts: 674
Mein Auto: 1999 740i
I too have no smog limits in NM. However, when cats clog up Im planing on running these http://www.frozenboost.com/product_i...5fb74b5b66745c

They look the part and are not expensive at all. If you cant afford that then just have a muffler shop straight pipe it. You might get some post cat O2 sensor codes but nothing to worry about. The post cat sensors only tell the computer how while your cats are performing there job, and do not effect anything. If you dont want the CEL in your face all the time you can install an O2 eliminator/simulator on your post cat sensors and you wont trip CEL. I ran one for years on my superchaged 540 with no cats, and no CEL.
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  #5  
Old 04-03-2013, 08:52 PM
Celthorseman Celthorseman is offline
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Location: La Grange, CA
 
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Mein Auto: 740i
mind at ease

Thank you all for your replies. I had a friend tell me that if I was to straight pipe my 740 that all kind of sensor issues would ensue therefor after.

As it sits my girlfriends sister is seeing a guy that has a shop and said that he will straight pipe for me, and told me about the post cat sensors. He looked up all the parts and ordered them today. It is looking like my cat issues will be no more as of mid next week. I am very excited about this. I am also wondering if getting rid of the cats will add a different tone, or more volume.

Did any of you all hear a difference at all?
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