Looking for results of Cat removal without a Tuner
Account Retired
Joined: Oct 2009
Posts: 3,245
Likes: 12
From: Here
SpiderPig,
I was going to do this mod to a 2010 2:1. I got a full exhaust system off Ebay and started looking at how I would go about it. After some measuring and design assessment I decided against it for a few reasons. The area housing the catalyst is a relatively large cross section compared to the primary tubes, after removing the catalyst it would act as an expansion chamber, which is counterproductive. I noticed the outlet after the collector was an 1/8 smaller I.D. than the primary tubes, so it was actually a choke point in the system. The arrangement of the two primaries was offset in a manner that I felt would not promote complimentary scavenging. I have a fully equipped welding and machine shop at my disposal, but by the time I could correct all of these shortcomings, I would basically be building a new set of pipes, so I bought the FM 2:1 head pipe instead. I was able to use the shields and OEM muffler from the system I purchased so it wasnt a total loss. In fact it turned out to be a very good system. Im not sure if you are working on a 2:1 or 2:1:2, but I think they both have the same characteristics that I identified. It is doable, but after very serious consideration, I decided it wasnt worth it. Weather it is core drilled or cut in half and completely gutted, you will probably end up with a cooler running pipe, but I doubt it will flow freely.
I was going to do this mod to a 2010 2:1. I got a full exhaust system off Ebay and started looking at how I would go about it. After some measuring and design assessment I decided against it for a few reasons. The area housing the catalyst is a relatively large cross section compared to the primary tubes, after removing the catalyst it would act as an expansion chamber, which is counterproductive. I noticed the outlet after the collector was an 1/8 smaller I.D. than the primary tubes, so it was actually a choke point in the system. The arrangement of the two primaries was offset in a manner that I felt would not promote complimentary scavenging. I have a fully equipped welding and machine shop at my disposal, but by the time I could correct all of these shortcomings, I would basically be building a new set of pipes, so I bought the FM 2:1 head pipe instead. I was able to use the shields and OEM muffler from the system I purchased so it wasnt a total loss. In fact it turned out to be a very good system. Im not sure if you are working on a 2:1 or 2:1:2, but I think they both have the same characteristics that I identified. It is doable, but after very serious consideration, I decided it wasnt worth it. Weather it is core drilled or cut in half and completely gutted, you will probably end up with a cooler running pipe, but I doubt it will flow freely.
Road Warrior
Joined: Mar 2007
Posts: 1,383
Likes: 3
From: Texas City, TX
When I was researching my bike, they weren't putting cats in the exhaust yet but for very few exceptions. The general consensus was, you could change the mufflers or the intake without adversely effecting the stock fuel ratios. The opinions were that the system could compensate for a change in one or the other. Change both however, and you'd probably be better off going with some kind of EFI programmer too. PCV or SERT etc.
Assuming all of that is true, and I've not read anything to make me believe that it wouldn't be, I can't seeing "just" removing the cat from the exhaust system hurting anything. Keep the stock air cleaner and mufflers and you should be good to go. One has already testified to an improvement in performance. I wouldn't have bet on that one way or the other but it's good to hear. On the heat side of things, catalytic converters by their nature, run very hot. If they didn't, they wouldn't work. Removing the CC couldn't help but reduce the heat levels IMO.
Personally, I'd say go for it and let us know how it turns out!
Good luck & Ride Safe,
Steve R.
Assuming all of that is true, and I've not read anything to make me believe that it wouldn't be, I can't seeing "just" removing the cat from the exhaust system hurting anything. Keep the stock air cleaner and mufflers and you should be good to go. One has already testified to an improvement in performance. I wouldn't have bet on that one way or the other but it's good to hear. On the heat side of things, catalytic converters by their nature, run very hot. If they didn't, they wouldn't work. Removing the CC couldn't help but reduce the heat levels IMO.
Personally, I'd say go for it and let us know how it turns out!
Good luck & Ride Safe,
Steve R.
Outstanding HDF Member
Joined: Jan 2010
Posts: 2,916
Likes: 31
From: earth
Ronp42,
The origin of my calculations is no mystery; Using a Starrett 6 dial caliper I measured the inside diameter of the primary tubes and the inside diameter of the outlet after the catalyst chamber, applied some elementary math to compute cross section area for both and WALAH. The area of the outlet is significantly less than that of one of the primary tubes. So, I can tell you, that ANY flow application with a smaller diameter down stream, than the original inlet diameter is a restriction, hence my assessment of chokepoint. To expound on my theory of the empty catalyst area acting as an expansion chamber, I used the same type of measuring procedures and math to confirm much greater area than the TWO primaries combined. Hot, high velocity exhaust gas comes out of the primary, it enters the chamber where it slows and cools, then it has to be pushed to speed up again to exit the smaller outlet. Through the fast, slow, fast, cooling process, parasitic loss is introduced because it takes more energy from the motor to push the gas through the inefficient design. Lastly, the collector, just look at it, there simply is not a smooth, gradual transition from the two primaries to the single secondary tube, compare it to the collector of any 2:1 system by any manufacturer. Im confused when you say you did what I decided not to and then you say you bought a pipe off Ebay. If you bought an OEM header that had the cat removed, then it sounds to me like you paid someone else to do what I decided not to. Can your claim of performance improvement be quantified and supported with before and after Dyno slips, or is just what you feel. The addition of your high flow muffler alone would be a seat of the pants noticeable gain, even without cat removal. Put the OEM muffler back on and see how it feels, compared to stock. I never intended to imply this was a useless mod or that no desirable characteristics could be achieved, and I definitely didnt intend to offend anyone who has performed this mod. Kudos to You and Your mod, Im glad you were satisfied with the results. I simply wanted to share my observations with the OP, who did in fact ask about the cat removal mod. I started my project with a different goal in mind than the OP, but many of my observations were relevant to the inquiry. The time and effort required to do what I wanted to do, was not cost effective compared to buying a pipe. All that being said this mod will offer some modest gains, but even with no dyno proof, I am confident it will not flow as well as the worst performing aftermarket 2:1 headpipe.
The origin of my calculations is no mystery; Using a Starrett 6 dial caliper I measured the inside diameter of the primary tubes and the inside diameter of the outlet after the catalyst chamber, applied some elementary math to compute cross section area for both and WALAH. The area of the outlet is significantly less than that of one of the primary tubes. So, I can tell you, that ANY flow application with a smaller diameter down stream, than the original inlet diameter is a restriction, hence my assessment of chokepoint. To expound on my theory of the empty catalyst area acting as an expansion chamber, I used the same type of measuring procedures and math to confirm much greater area than the TWO primaries combined. Hot, high velocity exhaust gas comes out of the primary, it enters the chamber where it slows and cools, then it has to be pushed to speed up again to exit the smaller outlet. Through the fast, slow, fast, cooling process, parasitic loss is introduced because it takes more energy from the motor to push the gas through the inefficient design. Lastly, the collector, just look at it, there simply is not a smooth, gradual transition from the two primaries to the single secondary tube, compare it to the collector of any 2:1 system by any manufacturer. Im confused when you say you did what I decided not to and then you say you bought a pipe off Ebay. If you bought an OEM header that had the cat removed, then it sounds to me like you paid someone else to do what I decided not to. Can your claim of performance improvement be quantified and supported with before and after Dyno slips, or is just what you feel. The addition of your high flow muffler alone would be a seat of the pants noticeable gain, even without cat removal. Put the OEM muffler back on and see how it feels, compared to stock. I never intended to imply this was a useless mod or that no desirable characteristics could be achieved, and I definitely didnt intend to offend anyone who has performed this mod. Kudos to You and Your mod, Im glad you were satisfied with the results. I simply wanted to share my observations with the OP, who did in fact ask about the cat removal mod. I started my project with a different goal in mind than the OP, but many of my observations were relevant to the inquiry. The time and effort required to do what I wanted to do, was not cost effective compared to buying a pipe. All that being said this mod will offer some modest gains, but even with no dyno proof, I am confident it will not flow as well as the worst performing aftermarket 2:1 headpipe.
Banned
Joined: Sep 2009
Posts: 7,580
Likes: 7
From: The Internet (& Dyer, Indiana)
I don't see how making such a big change could possibly behave the same with the original ECM map.
Big risk, using same map. Better have some back-up cash available for a tuner, if you decide to take the chance. (Just in case).
Big risk, using same map. Better have some back-up cash available for a tuner, if you decide to take the chance. (Just in case).
Account Retired
Joined: Oct 2009
Posts: 3,245
Likes: 12
From: Here
Ronp42,
The origin of my calculations is no mystery; Using a Starrett 6 dial caliper I measured the inside diameter of the primary tubes and the inside diameter of the outlet after the catalyst chamber, applied some elementary math to compute cross section area for both and WALAH. The area of the outlet is significantly less than that of one of the primary tubes. So, I can tell you, that ANY flow application with a smaller diameter down stream, than the original inlet diameter is a restriction, hence my assessment of chokepoint. To expound on my theory of the empty catalyst area acting as an expansion chamber, I used the same type of measuring procedures and math to confirm much greater area than the TWO primaries combined. Hot, high velocity exhaust gas comes out of the primary, it enters the chamber where it slows and cools, then it has to be pushed to speed up again to exit the smaller outlet. Through the fast, slow, fast, cooling process, parasitic loss is introduced because it takes more energy from the motor to push the gas through the inefficient design. Lastly, the collector, just look at it, there simply is not a smooth, gradual transition from the two primaries to the single secondary tube, compare it to the collector of any 2:1 system by any manufacturer. Im confused when you say you did what I decided not to and then you say you bought a pipe off Ebay. If you bought an OEM header that had the cat removed, then it sounds to me like you paid someone else to do what I decided not to. Can your claim of performance improvement be quantified and supported with before and after Dyno slips, or is just what you feel. The addition of your high flow muffler alone would be a seat of the pants noticeable gain, even without cat removal. Put the OEM muffler back on and see how it feels, compared to stock. I never intended to imply this was a useless mod or that no desirable characteristics could be achieved, and I definitely didnt intend to offend anyone who has performed this mod. Kudos to You and Your mod, Im glad you were satisfied with the results. I simply wanted to share my observations with the OP, who did in fact ask about the cat removal mod. I started my project with a different goal in mind than the OP, but many of my observations were relevant to the inquiry. The time and effort required to do what I wanted to do, was not cost effective compared to buying a pipe. All that being said this mod will offer some modest gains, but even with no dyno proof, I am confident it will not flow as well as the worst performing aftermarket 2:1 headpipe.
The origin of my calculations is no mystery; Using a Starrett 6 dial caliper I measured the inside diameter of the primary tubes and the inside diameter of the outlet after the catalyst chamber, applied some elementary math to compute cross section area for both and WALAH. The area of the outlet is significantly less than that of one of the primary tubes. So, I can tell you, that ANY flow application with a smaller diameter down stream, than the original inlet diameter is a restriction, hence my assessment of chokepoint. To expound on my theory of the empty catalyst area acting as an expansion chamber, I used the same type of measuring procedures and math to confirm much greater area than the TWO primaries combined. Hot, high velocity exhaust gas comes out of the primary, it enters the chamber where it slows and cools, then it has to be pushed to speed up again to exit the smaller outlet. Through the fast, slow, fast, cooling process, parasitic loss is introduced because it takes more energy from the motor to push the gas through the inefficient design. Lastly, the collector, just look at it, there simply is not a smooth, gradual transition from the two primaries to the single secondary tube, compare it to the collector of any 2:1 system by any manufacturer. Im confused when you say you did what I decided not to and then you say you bought a pipe off Ebay. If you bought an OEM header that had the cat removed, then it sounds to me like you paid someone else to do what I decided not to. Can your claim of performance improvement be quantified and supported with before and after Dyno slips, or is just what you feel. The addition of your high flow muffler alone would be a seat of the pants noticeable gain, even without cat removal. Put the OEM muffler back on and see how it feels, compared to stock. I never intended to imply this was a useless mod or that no desirable characteristics could be achieved, and I definitely didnt intend to offend anyone who has performed this mod. Kudos to You and Your mod, Im glad you were satisfied with the results. I simply wanted to share my observations with the OP, who did in fact ask about the cat removal mod. I started my project with a different goal in mind than the OP, but many of my observations were relevant to the inquiry. The time and effort required to do what I wanted to do, was not cost effective compared to buying a pipe. All that being said this mod will offer some modest gains, but even with no dyno proof, I am confident it will not flow as well as the worst performing aftermarket 2:1 headpipe.
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Big Kahuna HDF Member
Joined: Jul 2007
Posts: 28,128
Likes: 21
From: US poverty capital, california
Does your calc take into consideration the outside flow of air over the pipe while moving, creating a vacuum at the pipe outlet? that lower pressure area would help evacuate the pipe and probably overcome the "push" you speak of
