BMW R1200R R1150R/T F800 K1200R R1100R/T R1250R RnineT Message Board

65

Thanks for the info Yellowjacket. I am also contemplating a catalectomy. Looking forward to the sonic results, as well. Just a few tech questions to guide me:

-It sounds like your welds are not stainless. Since I have a limited welding knowledge; Are there any long term weld issues, since the collector is stainless (it is, isn't it?) and the welds aren't (i.e. different metals expanding and contracting at different rates until cracks form?)

-Were the reconstruction welds MIG or TIG?

-Is it possible or practical to only open the back section (where the actual catalyst is) and just remove the most restrictive and heavy component?

Thanks again and keep us posted,

cricman

34

cricman,

I'd also would have cut a trap door in the rear to remove just the restrictive catalyst honeycomb assembly as it looks like the collector portion of the internal "header" was destroyed. That, where the two exhaust pipes join to one, is where the OEM's invest their Rocket Science resources. That means there'll be zero alternate exhaust pulse scavenging - - - resulting in a significant power loss at low RPM and maybe a lower peak power curve. Of course, yellowjacket couldn't see thru the metal to make that decision at the start . . . . or could he?

The CatBox and muffler are Stainless Steel. I had my muffler's air tool cut open trap door welded shut, after I "relieved" the internal passageways, and he used stainless wire feed MIG.

4

Ok, guys, at the risk of really sounding stupid, which I can do and do often, why not just remove the cat completely rather than going thru all that trouble? Is this all for show? Just wondering.

yellowjacket,

"how could it be remedied?"

Too late for that with the damage I believe has been done. At least you still have your stock exhaust to use.

I also have concern that the O2 sensor is now out of the sampling stream and into the "room" of the CatBox where it may not control as it should. This may only be analysis paralysis as I see aftermarket OilHead exhaust systems without the 2-into-1 collector and with "in the room" positioned O2 sensors, but they are only concerned with nice looks, cool sound and peak power.

beemer-biker,
He wanted to improve the sound and performance --and-- do it on-the-cheap by using someone else's un-used (obtained for $25) stock exhaust.

YJ,
As I mentioned when this concept was revealed months ago, non-stainless filler rod used to weld stainless steel will most likely crack in the heat affect zone when exposed to repeated heating and cooling. This is especially true if stress relief and heat treating precautions weren't taken. Keep a close eye on the welds for cracks in the first month or so. If you get past that point you should be alright. The thick material might prevent the cracking potential.

Trust Rob on the airflow comments. This is not my area of expertise.

let us know how it performs and holds up. This is a good cost saving technique.

The Cat on my wife's R1200C started rattling last summer. Took me a while to figure out where it was coming from but after I was certain that it was insided the CAT, I priced a new exhaust system. Because both exhaust and the CAT are one piece on the R1200C, BMW wanted $1300.. &%#$@%#^@% No Way!
I removed the exhaust and took it took a friend who owns a welding shop. He cut it open and said that there was a lot of loose material in the CAT. Apparently, it was self-destructing. He removed everything that was inside and welded it back together. The bike runs cooler and the gas mileage improved by 2-3 mpg.

Hey Yellowjacket...thanks for the post and pics....good job.

DJ

beemer-biker wrote:Ok, guys, at the risk of really sounding stupid, which I can do and do often, why not just remove the cat completely rather than going thru all that trouble? Is this all for show? Just wondering.

CycleRob wrote: beemer-biker,
He wanted to improve the sound and performance --and-- do it on-the-cheap by using someone else's un-used (obtained for $25) stock exhaust.

Cyclerob,

I think he was asking why not remove the cat completely. I assume that one answer is that the O2 sensor plugs into the cat. Also, if you remove the cat and the exhaust, you need something to vent the exhaust gasses away from you, which means you are buying an aftermarket Y pipe or collector box or something like that. Hence, the cost savings achieved by gutting the cat instead of buying an aftermarket replacement. Is that what you mean?

rdsmith3 wrote:[

Cyclerob,

I think he was asking why not remove the cat completely. I assume that one answer is that the O2 sensor plugs into the cat. Also, if you remove the cat and the exhaust, you need something to vent the exhaust gasses away from you, which means you are buying an aftermarket Y pipe or collector box or something like that. Hence, the cost savings achieved by gutting the cat instead of buying an aftermarket replacement. Is that what you mean?

rdsmith 3, yes that was what I was going for, thanks. I have an aftermarket exhaust with no cat, that's what prompted the question in the first place. The other alternative, maybe, is to do what I think DJ did, remove the muffler, leave the cat in place and put a nice tip on the cat. Looks good, simple and I think has close to the same benefits, including weight savings, something not gotten by gutting the cat. Or at least, not as much.

I ran without a muffler for a while. I liked the sound, but I thought it looked not quite right. It is certainly the cheapest alternative, and certainly the best one if you use a full size case.

I put the muffler back on when I began commuting more. I can't really say why, except I think it looks slightly better with a muffler than without.

5

Yellowjacket,

Don't be so bummed out; you are the pioneer that I am going to follow on the path of my catalectomy (or is it circumcatalysion?)! You have done me a huge favor by rippin' that biskit open and exposing its heinous innards. Somebody had to do it first;...and you dared. You are, my friend, the Lewis and Clark, the Leonardo da Vinci, and the Neil Armstrong of the catalytic collector! You have, without a doubt, done something to benefit all of us interested in the project. Seriously, thanks for the time, the work, the information, and the inspiration.

cricman

p.s. Who wants to cut me deal on an converter they are not using for cheap?

4

Yellowjacket,

Thanks for the project and the effort you put into it, let us know how it sounds and runs.