Thoughts on Cat being restrictive......
Road Warrior
Joined: Nov 2006
Posts: 1,462
Likes: 121
From: Northern Illinois
The cat is exceptionally high flowing. Ceramic car cats use 50% of the space. The very tough and thin corrugated cats can be flattened to way less than 10% of the volume that they are in.
Most can not detect any change in the exhaust when the cats are removed because the flow is virtually the same.
Most can not detect any change in the exhaust when the cats are removed because the flow is virtually the same.
I have a good friend who has wrenched full time on Harley's for over 30 years. Currently he does most of the performance mods, and dyno tuning for a large dealership. He has never come across an aftermarket header that will outperform the stock cat head pipe.
Road Warrior
Joined: Mar 2008
Posts: 1,783
Likes: 10
From: Oh
I tend to listen to people that have spent thousands $$$ on R&D to test that theory, like Jamie at Fuelmoto over some one who "thinks" it doesn't matter. If you look at Fuelmoto's results the proof is in the pudding and I am talking about proven dyno tuned results. The convergence of exhaust gases into a cat in my opinion cannot not result in the same flow as without the cat, other wise they would put them on everything that races down at the dragstrip.
Ultimate HDF Member
Joined: Feb 2010
Posts: 8,039
Likes: 1,305
From: Jayhawk Country
I tend to listen to people that have spent thousands $$$ on R&D to test that theory, like Jamie at Fuelmoto over some one who "thinks" it doesn't matter. If you look at Fuelmoto's results the proof is in the pudding and I am talking about proven dyno tuned results. The convergence of exhaust gases into a cat in my opinion cannot not result in the same flow as without the cat, other wise they would put them on everything that races down at the dragstrip.
Road Captain
Joined: Dec 2006
Posts: 593
Likes: 4
From:
How did you get a Cat in your exhaust pipe? Did it just crawl up in there? I would think that it would make one hell of a noise when you started it up, not to mention the furr that would fly out of that thing.
Road Warrior
Joined: Mar 2008
Posts: 1,783
Likes: 10
From: Oh
Losing the heat from the cat was worth the purchase price for me and it has a lifetime warranty.
Tourer
Joined: May 2009
Posts: 270
Likes: 0
From: Dunstable, MA
This debate has been going on for years on the automotive side of the fence and the cats are not as restrictive as one might think.
Fuelmoto's head pipe is not a direct comparison as its still a high performance head pipe and is not a carbon copy of the stock one. To see true comparison you'll need to run a stock head pipe vs a stock head pipe with a cat removed.
Fuelmoto's head pipe is not a direct comparison as its still a high performance head pipe and is not a carbon copy of the stock one. To see true comparison you'll need to run a stock head pipe vs a stock head pipe with a cat removed.
Outstanding HDF Member
Joined: Jan 2010
Posts: 2,916
Likes: 31
From: earth
If it's not restrictive then why is my exhaust louder without the cat? Because, as a secondarry effect the cat breaks up and absorbs some sound waves.
If it's not restrictive then why is my exhaust cooler without the cat? Because, the cat operates on heat, It has to get hot for the catalyst material to covert harmful gases to inert gases, it captures and retains exhaust gas heat, when it's gone the heat is gone.
If it's not restrictive then why are the mufflers redesigned for the cat? Because, again the cat absorbs some sound, so the mufflers dont need to muffle as much as a non cat system.
Just look at the picture of the cat cut in half, that has to be restrictive. Yeah, look at it, closely, the total open area of the cat material mesh is more than sufficient area to support the volume of flow required by the primaries.
It's simply not restrictive.
If it's not restrictive then why is my exhaust cooler without the cat? Because, the cat operates on heat, It has to get hot for the catalyst material to covert harmful gases to inert gases, it captures and retains exhaust gas heat, when it's gone the heat is gone.
If it's not restrictive then why are the mufflers redesigned for the cat? Because, again the cat absorbs some sound, so the mufflers dont need to muffle as much as a non cat system.
Just look at the picture of the cat cut in half, that has to be restrictive. Yeah, look at it, closely, the total open area of the cat material mesh is more than sufficient area to support the volume of flow required by the primaries.
It's simply not restrictive.
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Outstanding HDF Member
Joined: Jan 2010
Posts: 2,916
Likes: 31
From: earth
This debate has been going on for years on the automotive side of the fence and the cats are not as restrictive as one might think.
Fuelmoto's head pipe is not a direct comparison as its still a high performance head pipe and is not a carbon copy of the stock one. To see true comparison you'll need to run a stock head pipe vs a stock head pipe with a cat removed.
Fuelmoto's head pipe is not a direct comparison as its still a high performance head pipe and is not a carbon copy of the stock one. To see true comparison you'll need to run a stock head pipe vs a stock head pipe with a cat removed.