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[1abastarsmda]

Did anyone else understand what he just said?  I just drilled out my CAT last night, so I've been pretty intimately involved with what's there are where things go, and that just confused me totally.

I understand that the CC is about 5 1/16" long and I'm assuming you are saying that the chamber where that is located is about 7" long.  After that, I'm not sure what you are saying.  When you remove the CC, it's all gone except a very small bit around the circumference of the pipe.  It's completely opened up after drilling out the CC.

Yes, the pipe splits back into 2 pipes after the CC, so there is only one CC to worry about.  Maybe I'm missing a point here.

[SBB]

Did anyone else understand what he just said?  I just drilled out my CAT last night, so I've been pretty intimately involved with what's there are where things go, and that just confused me totally.

I understand that the CC is about 5 1/16" long That makes senseand I'm assuming you are saying that the chamber where that is located is about 7" long.That also makes sense  After that, I'm not sure what you are saying.You have a 5" long CC in a 7" chamber  When you remove the CC, it's all goneThe only part gone is the part you drilled out. the chamber is an oval shaped chamber so the front and the rear pipe can merge together.  You only drilled out a part of the cat except a very small bit around the circumference of the pipe.  It's completely opened upWrong again after drilling out the CC.

Yes, the pipe splits back into 2 pipes after the CC, so there is only one CC to worry about.  Maybe I'm missing a point here.

See the picture below of the header

[1abastarsmda]

So, are you saying that you would have to cut out the bottom half of the edge of the cat converter to open it up or that you think there is another cc in the lower half of the chamber?  It seems that you are saying that the front pipe is still being partially blocked by the cc. 

[SBB]

So, are you saying that you would have to cut out the bottom half of the edge of the cat converter to open it up YES, if you want to open the pipe up completely![/color][/b] or that you think there is another cc in the lower half of the chamber?There is only one CC. It fills the entire oval collector area.  It seems that you are saying that the front pipe is still being partially blocked by the cc.Bingo!  We have a winner. Yes, after you drill out the part you can get to there will be more flow BUT, the front header will still have a restricted flow. 

[1abastarsmda]

With that being the case, I don't know why I bothered drilling the CAT out.  At that juncture, I think it would be worth the additional labor to get a set off a 96" and put them on here.  I know of one person off the top of my head that has ordered a new complete system for his new bike...I'm sure I could get his to put on mine.  I wonder what he ordered...I didn't think anyone had hit the market yet with a complete system.  Oh well...is it worth the labor to do this or not? 

While I'm at it, I have another somewhat related question.  When I ordered my Maxflo air cleaner, the gent I spoke with told me that if I removed my CAT, changed to Fullsac's in my mufflers, and changed my air cleaner...that I shouldn't even ride my bike as far as the dealer (about 14 miles) to get my SERT done.  I thought that I could ride it that way, but just a better set up when I get the SERT done.  He pretty much told me that I will damage my engine.  Can I ride it to the dealer or am I going to do some damage?

[GregKhougaz]

So, are you saying that you would have to cut out the bottom half of the edge of the cat converter to open it up YES, if you want to open the pipe up completely!   or that you think there is another cc in the lower half of the chamber? There is only one CC. It fills the entire oval collector area.  It seems that you are saying that the front pipe is still being partially blocked by the cc.Bingo!  We have a winner. Yes, after you drill out the part you can get to there will be more flow BUT, the front header will still have a restricted flow.  

 Guys, very good discussion...   My $.02:

           I think Jim Kerr mentioned this before, by using a drill to remove whatever % of the cat you're getting to, you're creating flow for both headers.  Air is a gas which when flowing, will follow a path of least resistance.  When I drilled mine, I could see into both headers.  The front header gas may have had to turn or bend more than the rear but it clearly had more flow than with cat.  The question is would removing this additional section of cat provide more flow?  Considering that the cylinders do not fire together, I do not think so though I have not measured.  Then, even if you get more flow.... the important question.... do you get more power?   Since the engine needs some back pressure, I again have doubts.  I can only say that from stock to no cat and fulsacs in one evening was a very noticeable difference.  Jim measured these and I think you can find his numbers (pre race tune).  

           On the last question, these mods and the A/C will give the motor more air, and not fuel so you will be running lean.  Under 4000 rpm's the closed loop system will try to compensate so a few miles to the dealer should not have any effect or damage.  But get the tune done asap to richen up your a/f mixture.  (OK, $02 x 2)  

[SBB]

Guys, very good discussion...   My $.02:

           I think Jim Kerr mentioned this before, by using a drill to remove whatever % of the cat you're getting to, you're creating flow for both headers.  Air is a gas which when flowing, will follow a path of least resistance.  When I drilled mine, I could see into both headers.  The front header gas may have had to turn or bend more than the rear but it clearly had more flow than with cat.  The question is would removing this additional section of cat provide more flow?  Considering that the cylinders do not fire together, I do not think so though I have not measured.  Then, even if you get more flow.... the important question.... do you get more power?   Since the engine needs some back pressure, I again have doubts.  I can only say that from stock to no cat and flasks in one evening was a very noticeable difference.  Jim measured these and I think you can find his numbers (pre race tune).  

           On the last question, these mods and the A/C will give the motor more air, and not fuel so you will be running lean.  Under 4000 rpm's the closed loop system will try to compensate so a few miles to the dealer should not have any effect or damage.  But get the tune done asap to richen up your a/f mixture.  (OK, $02 x 2)   

 

[TN]

looking at the pic in post from sb the left black mark shows where the cc starts. now go over 5" and thats where it ends. the chamber is 7". capish.

the collector still has about half of the cc left after drilling.
 the front headpipe is unobstructed for flow, well maybe 96%.

bwtfdik


TN

[guppytrash]

Have you ever heard the saying:  Measure it with a micrometer, mark it with a paint brush, cut it with a chain saw, and fine tune trim it with an ax.

Ya gotta let it go man, ya gotta let it go!

I removed my CC and then had my exhaust balanced, blueprinted, polished and ported.

I now feel comfortable in knowing that my exhaust is the highest performance part of my 45 degree air cooled  v-twin touring motorcycle.

Do you see a BIG picture?   Really do you think that whats left in the exhaust is holding ya back!

[dartman]

GT, You hit the nail on the head, My old dinosaur Motors torque band ends about 4500 rpms,  im sure with just an air cleaner, tuner and exhaust it has no clue that there is still a minor obstruction in the head pipe.

[Jim Kerr]

I agree with the last several posts.  There is no material difference in the exhaust after the cat has been drilled. What makes the 96" swap-out a waste of time, money and effort in my mind is the OEM header design itself.  It makes a hard/narrow 90 degree turn to get to the left side.  The OEM design most certainly creates significantly more back-pressure than a small amount of cat material that remains in the collector.  Cat in or out makes no difference in this regard.  The majority of the exhaust is going to exit out of the right pipe if it is opened up with free flowing baffles.  It is the path of least resistance... 

FWIW, spending money to buy/install a 96" header without a cat is pointless.  Why spend money on something that will not add any value?  It is not better looking, it will not make any difference in performance, etc.  For those of you that just have a problem with having any portion of the cat in the collector, my recommendation is to wait until the after market Co's release a header/pipe combo that is actually designed for the 09's.  In the meantime, a cheap drill bit and some elbow grease will free up those horses and make you smile ever time you punch the throttle. 

[1abastarsmda]

I guess that answers my question.  However, I wasn't planning on spending anything to put the 96" pipes on, other than some new exhaust gaskets.  I can get a set for nothing and I would put them on myself, but it there is nothing to gain from it, why go through the headaches?  Since it's winter and I can't get much riding in anyway, and while I'm in "change the exhaust" mode, I figured this would be the time to do it, if it was ever going to get done.  Once I put it all back together next week, I'm done playing with the exhaust.

[1abastarsmda]

Of course, I just had another thought.  If the front exhaust is now being somewhat diverted and passing over the lower part of the CC, and now pretty much all of the exhaust is now flowing together with the rear exhaust and mainly out the right side pipe, we have basically created our own 2 into 1 pipe, with some leakage to the left side pipe.  Like I said, just a thought.

[Jim Kerr]

Of course, I just had another thought.  If the front exhaust is now being somewhat diverted and passing over the lower part of the CC, and now pretty much all of the exhaust is now flowing together with the rear exhaust and mainly out the right side pipe, we have basically created our own 2 into 1 pipe, with some leakage to the left side pipe.  Like I said, just a thought.

Yep, that's pretty much it.  The left pipe will generally only be needed when back-pressure builds up in the right side.  You can try an experiment if you like...  Let the bike idle and then put your hand behind the exhaust of the left side and then the right.  You will feel air from both sides, but there isn't as much coming out of the left side.  Another test is to have someone rev the engine and watch the air shooting out of the back.  The right side clearly pushes more air than the left.  This happens even on the stock bikes with no exhaust modifications as well. 

BTW, this is actually a good thing.  Two into one exhaust tend to out perform dual exhaust systems.  The exhaust gases are accelerating straight out versus having to turn.  In other words, if one cylinder has to work harder to expel the gases it will lower the power output of the engine.  2 into 1 enable the exhaust exit equally for both and it creates less turbulence in the pipes.  In our case, back pressure will build in the right pipe and then relieved in the left.  This helps with torque and keeps both of the cylinders preforming equally.  Path of least resistance thing again. 

[Jim Kerr]

BTW, another case in point on the right pipe being used more than the left is to look at the OEM baffles being pulled out of the bikes.  In my case, the left OEM baffle looked brand new while the right one clearly showed signs of heat and wear (this is most visible in the center where the exhaust changes direction).

The left side is only under a load when back pressure builds in the right pipe, which forces air to take the path of least resistance (e.g. the left 90 degree crossover).  When we swap the right side to free flow baffles we remove the majority of the back pressure.  This is why everyone sees such a remarkable difference in performance after installing Fullsac's and drilling the cat.  It was a night and day difference on my bike.  It was like I installed a different engine.  I'm consistently beating rice rockets on my bagger with zero engine mods