Open pipe cat only setup?
 

Just wondering if anyone here has tried an open pipe setup on the R11s with just the cat running. How loud it is and how well it runs. Also wondering how much baffling there is in the cat compared to the muffler because I know a cat only setup is possible on some bikes due to higher amounts of baffling in the cat.

Watch out the BMW noise Police are going to come after you. You can only do that if you are wearing your your safety green Aerostich suit.

it will most likely run lots, lots slower.
it will definitely be loud enough to get a ticket within the first 100 miles. (or get you shot).
you might be shin-kicking the motor by running so short on exhaust. if'n i were a valve, i wouldn't like you much if you did that. i might try to vacate the premises.

why do you want to run naked from the cat back?

with the stock catalytic in place you could run no muffler and it would be pretty darn quiet, no much louder then stock. However if the cat is hollowed out it would be stupid loud. However the flow dynamics will be adversely affected with a straight pipe or no pipe after the catalytic.

really bobby, that big old tuna can has that much ***** inside it?

man, am i glad i castrated mine soon after delivery.

surely the recently released research on cow farts vs. vehicle emissions shows that the bovines are damaging the ozone way more than my recently-rarely-ridden murdercycle.

and before any of ya peta-kissing-tree-huggin'-ozone-sucking zombies attack me....know this:

i EAT those cows. gladly. buy me a steak, i'll woof it down for ya. no problem.

....proud to do my part to cut down on ozone depletion.

actually, i turned the cat convertor into the recycle guys, and i assume it's now been transformed into thousands of Bag Balm cans.

I was thinking of modifying a small car muffler like a single chamber 40 series flowmaster(even though i loathe them) to install in place of the cat. Then put a little shorty tip to kick the exhaust out off to the side in front of the back tire.

If you do decide to try this please post your results.

Doesn't quite jive with my experience of removing my cat and keeping the stock mufflers in place. The sound got "slightly" louder, with a bit more throat to it, but not even close to a Laser or other system with aftermarket mufflers. Based on this, it would appear that most of the muffling is being done by ... the mufflers.

On the BMW parts fiche what people generally refer to as the cat is actually called the front muffler. Recently, I've been running a front muffler only setup on my 1150GS, it really is only slightly louder than with the full exhaust. The bike runs great, can't really notice a seat of the pants difference in performance. The reason I tried it was to put a full bag setup on the left side without spending $600. One thing I did with mine was to machine a small tip to match the same I.D. as on the stock muffler exit.

Mark, do you have and pictures of your set-up?

I'll try to take some tomorrow.

Thx for the replies.

The reason I was asking about this setup is just to see all of my options as far as exhaust. The only aftermarket setup I can find in Vancouver is the Two Brothers Racing sets, be it cat eliminator or slip-on. The slip-ons start at 750.00 so not too cheap, but still do able. I was curious about the Cat only setup because I've heard of the success of it with the 1150 gs.

My main issues are that I want the bike to be a bit louder, no louder then an aftermarket slip-on or full cat eliminator setup, just make the bike a little easier to notice when I'm riding beside day-dreaming cagers here in Vancouver who never seem to look anywhere but staight ahead.

But as well, I dont want to lose any performance out of the engine. I'm not too worried about gaining performance although the weight loss would be nice.

Keep an eye out on EBay, you should be able to find a take off aftermarket system for $400-800 depending on the system. I'd leave it stock or go with the whole system as the benefits are minimal to do it half-assed IMHO.

What I would love is something similar to this.http://forums.pelicanparts.com/uploa...1200426268.jpg

hey coffey, I like that! looks like that's an RT or R? how's that sound and who's is it?

I've always been a fan of Buell's exhaust placement and have always wondered why it never caught on for the R bikes where it seems such a clean fit. I can only recall ever seeing one shot on some German website of a GS (maybe not the right bike for this application, but..) with an underslung can.

utilizing the cat re-gains a bunch of weight I've already disposed of, but that's such a retardedly elegant solution that I might just try it this weekend.... I have visions of reconfiguring the underseat area with a mig welder to make it actually hold something useful. go figure, but I'm actually used to the underseat storage on my RC51

cheers
carlos

...it's the length of the pipe that is the problem in this case... the resonating air... it is tuned to the engine... messing around with the pipes on our boxers can produce some really unwanted results...

I agree with John and disagree with Bobby. There isn't very much muffling going on in the cat. Running an open pipe is just too damn loud, whether it's a Harley chopper or a BMW twin. The cat may take the edge slightly off it, but it's going to be LOUD.

- Mark

ralf, i mentioned the close priximity to valves previously, but nobody else seems to have an issue with it.

i guess stuff like engine back pressure, heat transfer and sonic wave influences on 4-stroke motors is too old school. dang, and all that time i thought it was real info.

PS: hey Ralf, aren't you supposed to be fleeing the country in the next few days? Hiding in the Bahamas under an assumed name?

Stock Cat and Muffler weight in at 27 lbs.

Stock Cat and Muffler weight in at 27 lbs. Plus without dyno runs you are guessing.

Has anyone here actually heard a BMW 1100/1150 with only a Catalytic converter installed and no muffer???????????????????


While I am assuming the rest of you are strictly discussing theory, I have heard several boxers with oem Cat installed and no muffler. With Catalytic only installed it's not that loud, no where near as loud as my full Akra on my HP2, no where in the ballpark of my BC2 Lasers or the Ztechnik I've had installed, as a matter of fact it's not as loud as any full system I've ever tried on an R11S. This is far from a recommendation to try it, but I do have a buddy with a chrome slip-on dildo tip purchased from your local tex-mex parts store on the end of his 1150GS cat and no muffler. It works for him and sounds fairly normal compared to most aftermarket full systems which eliminate the oem cat.

...and with the exhaust emitting approximately 30 inches closer to the ground, why heck that woud help slow down global warming, it'd get to the ozone layer just that much later, Al Gore would invent it.....ooops....wrong thread....then again...maybe not.

sure wish i hadn't found out that my $1,500 staintune system can be swapped out by a $4.99 baloney cut chrome pipe at pep boys.

what time do they close?

Yep. I played with modifying a stock system before i shelled out te $$ for a used Staintune (think I paid $650). Ran the bike with no rear muffler, just cat and up pipe, I was surprised how quiet it was. I went ahead and gutted the rear mufflers, still too quiet, so I gutted the cat, and there still was very little increase in the sound over stock. So Staintune it was.

Remember it is not just the sound level, but the tone that is music to your ears, and I think that tone would be missing from that stubby set up.

OK, so two of us have actually heard an 1100 boxer with only the factory cat installed and say from personal experience that it's pretty quiet in relation to aftermarket full systems vs others with "theories". I personally think leaving the stock exhaust alone is a better solution then trying to manipulate the factory guts, but the best option for me has been a good quality aftermarket full exhaust system (and for the record to the original poster Two Bros is the lowest on my list of worth while replacements, not that my opinion necessarily matters, lol)

...you guys must be deal or near deaf.... when I took off the cans with the cat installed, it was considerably louder than with the cans installed... then I mounted the Two Bros. Cat eliminator and it was louder and deeper yet...

Now, loud might mean something different to soem than it does to others... but it is NOT quiet with no cans cat or not...

Have you heard my BC2 full race system lately? lol That's loud. Loud is every Harley with an aftermarket pipe, not so loud with stock pipes, but louder then any BMW. I would put the Harley with stock pipes in the same realm as a boxer with factory cat only installed,.....louder then stock, but not remarkably.

My 1150RT with the Laser full system is louder than my GS with only the cat. And the cat only GS doesn't backfire on the over run like the Laser or Staintune full systems. My best sound preference on R bikes has been the cat/Staintune slip-on combo.

Actually, the Akra Exhaust on my 12 has a really nice growl to it... but then, I have never heard that one with the stock exhaust...

Yes everyone's opinion matter, hearing everyones thoughts on the matter is why I asked the question. I just wanted to make sure that I wouldn't damage the engine if I tried it out. Nothing is ever written in stone as far as modifying the bike, for the most part. My plan is simply to make sure that I don't change anything that I can't change back if and when I want to trade it in or sell the bike (not for many year I think)

Again thanks for everyone's input, and please keep it coming.

...not expensive enough?

I have had the 2 bros cat eliminator since I got the 11S (first mod... well, second, after the cannister-ectomy) and it works fine, fits well and gets just as golden as any other pipe... yet, I only paid about $270 delivered!

Works for me...

The Two bros cat eliminator is the exception, their product quality and more importantly customer service on the cans is another whole story

Ah, I see... well, Bobby... I have never had the "pleasure" of experiencing their customer service... nor do I have their cans, but you are right, I have heard some concerns about the quality of their cans... they sure look good, though!

But good quality customer service seems to have become more the exception that the norm these days, ANYWHERE... sad to say!

I bought and then sold a Staintune for the GS when I read on Adventure Rider that some guys have over 50k miles with only the cat and no adverse issues with the motor. I'm not sure if it may decrease the hp a bit as some say but they never commented on it and I'll find out soon. I ran it in the garage with only the cat and isn't much louder than stock. That cat is till very heavy so I'm looking at a system from Hattech that has a smaller cat and has un up-pipe that will work with the full sized left Jesse's that I just installed.

I want them to mate this cat ....

http://www.hattech.de/bmw_R1150GS_system12.html

to this up-pipe ....

http://www.hattech.de/bmw_R1150GS_system_U2.html

They are in Asia till the end of the month so I won't know till then