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Old 03-10-2010, 08:09 AM
 
14,777 posts, read 34,597,131 times
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Quote:
Originally Posted by Tightwad View Post
It's not about emissions. it's about engine back pressure that is required for the computer to sense fuel mixture and engine valve life.
Absolutely incorrect. Cats exist for one reason and one reason only, to control emissions from the car. The car is tuned with this in mind and is programmed to account for the cat. If you remove the cat, as I said in the post above, you simply need to retune the engine PCM or otherwise trick it into thinking that the cat is still there. By removing the cats, you will gain horsepower, torque and MPG. However, this is illegal, even if you can tune the car to pass emissions without them installed.

Maintaining proper backpressure is a whole other matter and is very vehicle specific as to the proper size of the exhaust system.
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Old 03-10-2010, 04:19 PM
 
Location: Vancouver, B.C., Canada
10,715 posts, read 22,379,800 times
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Originally Posted by NJGOAT View Post
Absolutely incorrect. Cats exist for one reason and one reason only, to control emissions from the car. The car is tuned with this in mind and is programmed to account for the cat. If you remove the cat, as I said in the post above, you simply need to retune the engine PCM or otherwise trick it into thinking that the cat is still there. By removing the cats, you will gain horsepower, torque and MPG. However, this is illegal, even if you can tune the car to pass emissions without them installed.

Maintaining proper backpressure is a whole other matter and is very vehicle specific as to the proper size of the exhaust system.
good point I know ford and GM small blocks opposite in that fords like some backpressure
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