don't forget the O2 sensors... (archive)
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Posted by Lez on August 21, 2000 at 11:13:00:
In Reply to: Question for Loren, or anyone else... posted by Emir on August 20, 2000 at 19:33:35:
(posted from: ppp-118.shadow.net (207.17.58.138))
if your car is pre-96 then no problem removing the cat. but later date ... you will have a drop in performance ! The reason is the OBDII system. The O2 sensors are located before and after the cat and they are comparing the data. If you remove your cat the rear O2 will "think" the cat isn't working, so it'll light up the check engine light and reduce the power so the emission will be better. Also you'll experience a sudden drop of fuel economy and lack of acceleration.
In pre-96 cars all of this isn't true, and you'll gain approximately 2-3 HP (just removing the cat) and additional 3-4 if you replace the complete exhaust system to a high performance. The exhaust pipe on the 8 series is 2.75" so big enough. On the turbo engine however you could gain a lot of power just to replace the header+exhaust pipe because of the reduced back-pressure. On regular engine's not much but one thing is true, most of the gain comes in the mid-range which is the best. Most of the times just replacing the exhaust pipe+header will not gain too much, but with other mods it could make a difference. Exhaust - muffler wear ? I can't tell you about that. I don't think the you'll see premature wear on your muffler because if you remove the cat the temp. will drop in the exhaust pipe, which is a good affect on the muffler... but that might be not true...
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