Open pipe cat only setup?

[Coffey]

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.

[lht]

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.

[bradzdotcom]

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?

[BMW Atlanta]

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.

[bradzdotcom]

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.

[Bigred455]

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.

[John Lyon]

Originally Posted by BMW Atlanta

with the stock catalytic in place you could run no muffler and it would be pretty darn quiet, no much louder then stock.

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.

[mfbRSV]

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.

[Bigred455]

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

[mfbRSV]

I'll try to take some tomorrow.

[Coffey]

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.

[BMW Atlanta]

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.

[Coffey]

What I would love is something similar to this.

[bigscience]

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

[signit98]

Originally Posted by bigscience

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.

...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...

[markjenn]

Originally Posted by John Lyon

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.

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

[bradzdotcom]

Originally Posted by bradzdotcom

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.

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?

[lht]

Stock Cat and Muffler weight in at 27 lbs.

[lht]

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

[BMW Atlanta]

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.