Thoughts on Cat being restrictive......
Tourer
Joined: Jul 2008
Posts: 491
Likes: 1
From: Mass.
I can't imagine that there would be any difference noticed ( except for sound ) by those folks that did nothing other than gut the cat and the rest of the bike was unchanged. Being that the aircleaner is so restrictive in the first place it would be a " limiting reactant " ( if you will ) in the whole subject . Just curious if that would be the reason that some insist no noticable change and some insist a quite obvious one .....
Last edited by Tele00; Aug 15, 2011 at 01:08 PM.
Extreme HDF Member
Joined: Jun 2011
Posts: 10,216
Likes: 224
From: Glendale AZ
I gutted mine a couple weeks ago and got it out on the open mountain roads yesterday. I did not notice any power increase or decrease. It was def louder almost but not quit like a pair of slip ons. Heat has decreased considerably which was my main reason for removing it. If I can decrease the temp then I have lowered my oil cooking culprid. I plan to keep it stock as its got plenty of power for me...my 2cents
Road Warrior
Joined: Aug 2009
Posts: 1,889
Likes: 104
From: Mississippi
I'm sorry but you cannot agree to disagree, because I do not agree to disagree; it takes more than one person to have an agreement, and you can't agree for me on my behalf. The phrase agree to disagree suggests a possibilility that either of us could be wrong or could be right, but you are just technically incorrect. You are free to be wrong and believe you are right, and I will make no further attempt to convince you otherwise either. I did try to provide you a rational and logical explanation for why the reasons you believe the cat is a restriction are not accurate, but as the good warden said, "some men you just can't reach". No hard feelings here.
"shakin' the bush Boss"
"shakin' the bush Boss"
Grand HDF Member
Joined: May 2006
Posts: 3,636
Likes: 1,208
From: Ohio
To argue that all that material in the head pipe is non-restrictive simply doesn't make sense. Look at it...it's self evident. It may not be the most restrictive thing but it definately restricts flow. The stock air cleaner may restrict more but as soon as you change the air cleaner and mufflers the cat becomes the restriction point. Just look at it and explain how there are not standing exhaust waves in the pipe. Explain how you can chemically convert exhaust gases without restricting flow. Why don't they run cats on race cars or race bikes?
Road Master
Joined: Jun 2006
Posts: 812
Likes: 0
From: Jaw-Jaw (Near The BIG Chicken!)
You can buy all the heat deflectors you want and they will still not give you the heat relief that removing the cat will. You would have to buy one that hangs down past the passangers foot rests to do any good. The wife is very happy by not having her feet burned off when we go riding. When Mama's happy, everybody's happy.
Seasoned HDF Member
Joined: Jul 2007
Posts: 6,336
Likes: 67
From: SW Minnesota
Just an observation on the dyno chart: So far, everyone is looking at hp increase.
Let's take a look at torque increase, not as a number but as a percentage. The change in headpipe is giving a useable 6+ percent increase in torque (as well as hp on the top end).
How much do you have to gain to "feel it" in the seat of your pants? 6% is quite a bit, especially when it shows up in the rpm range that you ride in.
Let's take a look at torque increase, not as a number but as a percentage. The change in headpipe is giving a useable 6+ percent increase in torque (as well as hp on the top end).
How much do you have to gain to "feel it" in the seat of your pants? 6% is quite a bit, especially when it shows up in the rpm range that you ride in.
Stellar HDF Member
Joined: Aug 2008
Posts: 2,404
Likes: 11
From: Southern Nevada (Pahrump)
Those CATS are restrictive. I took my V&H Hi-Outputs off my Limited when I traded it in & put them on my 08 RoadKing & their considerably louder! My 11 Limited has a CAT, my 08 RoadKing does not. My brother & brother in law are both running the same mufflers & both of their bikes are considerably quieter which to me indicates the CAT is the restriction. JMHO
Tourer
Joined: Sep 2010
Posts: 471
Likes: 9
From: Far NorCal
Over the years building race cars and running race cars I have come into a lot of cat contacts.
In the real world of racing, the cat is restrictive.
Many times we tested back to back....(4-8 hp is worth a straightaway pass). On the drags it was almost 2/10th better without.
My bike feels stronger without and respond is better....1200* cat heat is removed, worth the whole deal to me.
The track is real world, not the dyno, however I do dyno a lot, but for other reasons.
Just my 2 cents.....
For your street driven m-c, so what, speed limits are 55-60-65-70-75!
Leave them if you don't mind 1200* below you or wrap them.
In the real world of racing, the cat is restrictive.
Many times we tested back to back....(4-8 hp is worth a straightaway pass). On the drags it was almost 2/10th better without.
My bike feels stronger without and respond is better....1200* cat heat is removed, worth the whole deal to me.
The track is real world, not the dyno, however I do dyno a lot, but for other reasons.
Just my 2 cents.....
For your street driven m-c, so what, speed limits are 55-60-65-70-75!
Leave them if you don't mind 1200* below you or wrap them.
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Tourer
Joined: May 2009
Posts: 270
Likes: 0
From: Dunstable, MA
Yes the cat can be restrictive but this restriction will never be seen with the flow of exhaust these motors produce, the engine is a giant air pump only so much can go in an so much can go out.
So Yes the cat can be restrictive but you need to reach a higher flow in exhaust to see the restriction (which is the flow a race car/boat/bike would see), example run water through a screen at a low/med flow, you'll notice little to no difference in the flow of the water, now do the same thing and turn the flow up and it will statter and probably tear the screen (depending on how high the flow is)
So Yes the cat can be restrictive but you need to reach a higher flow in exhaust to see the restriction (which is the flow a race car/boat/bike would see), example run water through a screen at a low/med flow, you'll notice little to no difference in the flow of the water, now do the same thing and turn the flow up and it will statter and probably tear the screen (depending on how high the flow is)
Cruiser
Joined: Nov 2009
Posts: 153
Likes: 0
From: Keithville, La. 71047
Well, I have read every post. Who gives a rats a$$. Heat is the only issue. If you want to ride solo because the OL refused to blister her feet and you do not mind your jewels sweating then do not remove the CAT. If you prefer the alternative get rid of the darn CAT anyway you can afford. The rest is just BS.