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Getting the cat out of a Fat Bob exhaust

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Getting the cat out of a Fat Bob exhaust

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  #11  
Old 04-01-2011, 05:02 PM
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Originally Posted by tomzilla View Post
i think it really depends on where the bike is sold. i know for a fact that california, and similar emissions states require more than others. for example. i live in valdosta ga, no emissions laws, but in atl there is and anything 96 and up must pass the sniffer. i think that could equate to the diffrence. im just going to cut open, gut and re weld the case. i did it on several car mufflers so im not affrid to do it on a bike. im only worried about bakc pressure and such, but there are baffles for this too .
You are most likely correct about that.

You could always build your own custom 2-1 pipes, I bought a baffle that was designed for an automotive exhaust. Only thing I could find cheap in 3", but works just fine. I did not even have to re-tune.
 
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Old 04-01-2011, 05:08 PM
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I don't have a link handy, but over on the CVO forum they talk about drilling the cat out with a large bit of some kind.
 
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Old 04-01-2011, 06:04 PM
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I never did a bike but in a car I drilled then out with a cement drill bit and broke the rest up with a long chisel
 
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Old 04-13-2011, 10:51 AM
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Does the cat in your pipe block only the top output pipe or also the bottom pipe too?
 
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Old 04-13-2011, 10:52 AM
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Originally Posted by DynaFat09 View Post
Does the cat in your pipe block only the top output pipe or also the bottom pipe too?

It is in the collector so both.
 
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Old 04-15-2011, 11:50 AM
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The state of epa in Illinois is such that all vehicles with obdII get tested. They plug in and test. All other vehicles would require a dyno type test, and they've stopped testing in this manner. HD bikes don't have before and after cat O2 sensors or any obdII device, so I would think the option of trying to dyno sniff our bikes is far off from happening. I'm getting a pair of khrome werks 3" HP + for my 2010 Bob, and I'll use a masonry bit on a hammer drill. I won't worry about getting every last bit of the cat out either. With most of it gone it will work fine. I saw posts in cvo section stating that fullsac in Arizona did back to back dyno runs before and after cat removal and found no gains on 96 inchers in basically stock trim. At the 90 horse level, restrictions were noticed, but without cats, they only got 5 more HP.
 
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Old 04-15-2011, 12:09 PM
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Borrowed this from another post. This might help some to get an idea of whats inside
 
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Old 04-15-2011, 01:05 PM
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I got a set of cat-less headers ('08) off eBay and fitted them yesterday. The exhaust noise is a LOT louder. Now that might be great for some people but I like the noise just-so and its now way too loud, plus it has a metallic, echoing quality to it I don't like.

Pretty sure this means that the cat must offer a fair amount of restriction but I can't live with that noise so its back to the headers with a cat for me. Good job I did find some cat-less headers and didn't butcher the stock ones.
 
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Old 04-15-2011, 02:08 PM
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Well, that might explain why khrome werks added more baffle material in this muffler. Did you try the stock mufflers to see if they could quiet it down? I have read that there are some baffled you could add in the headpipe just before the muffler. I had Flowmaster muffler on my Dakota that had that same hollow sound, and were outrageously loud. After a couple years I changed to a quieter muffler...
 
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Old 04-15-2011, 07:51 PM
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Originally Posted by Foxster View Post
I got a set of cat-less headers ('08) off eBay and fitted them yesterday. The exhaust noise is a LOT louder. Now that might be great for some people but I like the noise just-so and its now way too loud, plus it has a metallic, echoing quality to it I don't like.

Pretty sure this means that the cat must offer a fair amount of restriction but I can't live with that noise so its back to the headers with a cat for me. Good job I did find some cat-less headers and didn't butcher the stock ones.
As it was stated earlier the new cats have little to no back pressure. If you look at the tests for plugged convertors they are suspect at less than 1 1/2 PSI back pressure at idle (this is from a very general test I found a while back). They do change the sound but with no appreciable effect on performance.
 
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