Any harm in keeping the cat while changing the pipe?

[Grey Thumper]

Been thinking of getting a new slip-on, although I feel vaguely guilty about replacing the cat with a Y pipe. Any disadvantages to keeping the cat?

[riceburner]

Been thinking of getting a new slip-on, although I feel vaguely guilty about replacing the cat with a Y pipe. Any disadvantages to keeping the cat?

only the heat build up, which is only really an issue in the hotter areas of the world.

I'm currently running the cat by itself - I swear the bike is quieter than it was with the standard can on.....

mind you - my standard can rattled like buggery!

[Grey Thumper]

only the heat build up, which is only really an issue in the hotter areas of the world.

Just to clarify, so the cat is likely to run hotter with a less restrictive pipe? Good to know, since I do live in one of the hotter areas of the world.

[riceburner]

only the heat build up, which is only really an issue in the hotter areas of the world.

Just to clarify, so the cat is likely to run hotter with a less restrictive pipe? Good to know, since I do live in one of the hotter areas of the world.

no - I was referring to the "generic" heat build that is caused by the restrictions in the cat.

With an open pipe I'd guess the cat may well run a touch cooler because the hot gases can escape the cat more easily. With the standard can, they can't.


What ever you do - do NOT run a Y-piece with the standard can. The exhaust from the can will be VERY hot - hot enough to melt the OE panniers. (trust me on that).

[AirForceDirt]

on the heat topic (I know, hijack right?). I got curious today so after a decent length ride, I took the bike to work to make use of our IR thermometer. My Remus can (titanium/carbon fiber) was 145 degrees Fahrenheit; the header pipes were 460 degrees Fahrenheit. Didn't measure the y-pipe.

[KiwiRR]

My cat and standard pipe were replaced with a Remus Y-pipe and carbon can by a previous owner. I didn't like the noise/look and put the standard can back on with the Y-pipe. Has run great over the last two years and no probs with the panniers, albeit NZ summers may not be as hot as elsewhere in the world.

[challey]

riceburner wrote:

What ever you do - do NOT run a Y-piece with the standard can. The exhaust from the can will be VERY hot - hot enough to melt the OE panniers. (trust me on that).

Not to be argumentative, but I ran a Sebring Y-pipe with the OEM can and system cases for years with no problems. Maybe I was just lucky, maybe it was just the lower ambients of the Northern Hemisphere but I did not have a problem in 28,000 miles of varied riding, including some long highway trips and some stints in heavy summer traffic.

YMMV

Charlie

[riceburner]

riceburner wrote:

What ever you do - do NOT run a Y-piece with the standard can. The exhaust from the can will be VERY hot - hot enough to melt the OE panniers. (trust me on that).

Not to be argumentative, but I ran a Sebring Y-pipe with the OEM can and system cases for years with no problems. Maybe I was just lucky, maybe it was just the lower ambients of the Northern Hemisphere but I did not have a problem in 28,000 miles of varied riding, including some long highway trips and some stints in heavy summer traffic.

YMMV

Charlie

Sounds like you were lucky then.
I ran a Remus Y-pipe with the OE can for one trip to France from the UK and the exhaust melted a hole in the rear face of the pannier - I can only assume a freak eddie / vortex in the aerodynamics around that area caused that part of the pannier to feel the full heat of the exhaust gases.

oh - and as for being "argumentative", I can only speak and advice from my own experiences - as can we all.

[sweatmark]

The exhaust from the can will be VERY hot - hot enough to melt the OE panniers.

Discovered the effect of hot exhaust gasses on BMW System Cases last season:

Seems that one of two rivets holding my ZTechnik muffler's "cloisonné" badge fell out, leaving a very small (2-3mm) hole in side of can. Unfortunately, the badge-side of muffler is the bag-side... like the Colorado River slowly but surely eroding soil & clay to produce Grand Canyon, that little muffler hole huffed & puffed & melted a small hole through the backside of case, filling the interior with exhaust gasses and water vapor. The resulting condensation completely soaked and stained the bag's contents, melted plastic bag material, left a stink.

Somewhere I've got pics...

[sweatmark]

Found the pics...

What exhaust system leaks can do to your System Cases:

[jcridge]

Has anyone looked at back-pressure of the cat and muffler? I too would like to remove the cat in favor of better acceleration and less heat, but don't really want extra noise. I have read quite a few posts here on different variations of slip-ons, modified stock cans, stub pipes with cat, etc... But haven't been convinced that what BMW has given us isn't the best overall.

Keeping the cat and custom bending a straight pipe to exit below and beyond the left pannier is something I have been thinking about. Anyone done this? I would like to know if the noise level increased, or does it just change pitch. A lower tone, slightly louder would be ok.

As far as the Y-pipe with factory can burning the pannier, I would think a simple heat shield spaced on the back of the pannier would take care of that. But it is good to know that it can be an issue when tweaking the exhaust.

John

[boxermania]

jcridge

Keeping the cat and custom bending a straight pipe to exit below and beyond the left pannier is something I have been thinking about. Anyone done this? I would like to know if the noise level increased, or does it just change pitch. A lower tone, slightly louder would be ok.

Has been done many times, loss of about 18 pounds not louder sound but mellower, the tip can be sourced at ay auto parts store, needs to be 1.75 in diameter witha slight bend, inexpensive. You can even used the clamp/protector between the cat and the original muffler.

I saw the first one on Rat Bastard's bike at the first Beakster Bash (April '04), there have been many more since then.

Do a search

[rdsmith3]

I ran for a long time with no muffler, and many others have as well. The first proponent of that, IIRC, was djdownunder, going back to maybe 2002? I put the muffler back on for inspection, and decided I liked the looks better.

Others, like cyclerob, have removed some of the restrictions in the muffler, but kept it on for some back pressure.

Oh, and get rid of the cat