Mazda Miata (MX-5) This compact RWD model, offered with many engines options for those are who want to cruise with the top down in a base model, or hit the track in one of the high performance models, has been a popular model since its introduction.

Removing Cat

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Old 05-01-2012, 11:52 AM
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Default Removing Cat

What are the general thoughts on removing the exhaust catalyst ?


thanks,

gander10
 
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Old 05-01-2012, 01:04 PM
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Originally Posted by gander10 View Post
What are the general thoughts on removing the exhaust catalyst ?


thanks,

gander10
Personally I'm fond of breathing air which is as clean as possible; for the sake of the rest of us you share this planet with, please leave your catalytic converter in place.
 
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Old 05-01-2012, 01:34 PM
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More trouble than its worth in most cases. They are even trying to find ways to clean up race car exhaust.
If you are driving on the street, keep the cat. Your CEL and state inspection station will love you for it.
 
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Old 05-01-2012, 01:56 PM
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Hollowing out a catalytic converter or replacing it with a test pipe or straight section of pipe is a violation of Federal Law punishable by fines in excess of $25,000 and/or jail time for both the vehicle owner and the person doing the work.
Removing a catalytic converter will result, at most, in 5 HP in power improvement. However, hollowing out a catalytic converter will cause resonance problems. The symptom is most often seen as a hesitation, popping, or backfire at or about 3,200-3,500 RPM. Upon hard acceleration, the engine will appear to cut out for a split second as RPMs drop and a split second later recover and continue past 3,200-3,500 RPM. Additional symptoms are a loud and continual popping sound when the vehicle is allowed to decelerate under load and a whooshing sound that is delayed from or following the engine speed. This is due to the open chamber within the hollowed out catalytic converter case. It loads up and releases pressure in the exhaust system that acts almost as a capacitor. The open chamber allows the formation of standing waves within the chamber which reflects back toward the engine and causes the hesitation and miss in the RPM range.
Above from: ISUPAGE; Performance Exhaust System Basics

your factory catalytic converters are robbing horsepower from your engine by creating a huge restriction and excessive heat in your exhaust system. To combat that, aftermarket parts companies have come up with test pipes and high flow cats for many popular applications. companies like Berk Technology have streamlined their high flow catalytic converters to a point where they have been proven to flow exhaust gasses up to 87% as efficiently as their test pipes, which is only 1.3 horsepower less per 10 horsepower gained.
Above from: Test Pipes vs. High Flow Cats |

I would get a hi-flow cat 1/4" bigger than stock with an exhaust pipe 1/4" wider than stock to maximize flow. Make sure the exhaust before and after your cat is also 1/4" wider as well. Sound, flow and power should be realized. On my 3.0 litre V6 the stock exhaust is 2.25", mine is 2.5" and the single flow part. Any bigger would negate flow. Check out Magnaflow.
http://www.magnaflow.com/wideopen/performdata.asp
 

Last edited by UseYourNoggin; 05-01-2012 at 02:09 PM.
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