I'm not a fan of the look either, but that's what you get after TIG welding stainless steel, with purge gas in the pipe. A lot of the sportbike riders love that look. The discoloration can be buffed out to the same finish of the unwelded pipe if that's preferred.
Cut
My home made exhaust. I conducted many tests to achieve raw correct combination of baffles, glass pack, steel pack straight through and achieved both the sound I wanted and the look that does not distract from one of the R18s unique features, the exposed driveshaft. Every person that has seen my bike commented on how they like the looks of the exposed driveshaft. See attached photo.
You do nice weldiing. Did you have any issues with copper plating under the chrome?
Well thanks but credit goes to Al
A good "rule of thumb" answer to this age old question is if you're not messing with intake air or fuel or the cats, a simple muffler swap rarely effects the bike's running condition negatively to where it now requires a "tune" (getting the mix back just right). Note this question is usually answered by vendors and service departments in another way - because muffler change or not, tuning never hurts, because any of today's bikes will run cooler (and better) from a richer mix (more fuel at the expense of higher emissions); more importantly, that "other" answer ALWAYS provides a sale and a profit. Put the pipes on...leave the air box (and filter) alone and as David said it will (more than) likely be just fine! That said...once product is on the market a most excellent next step is eliminate the cats, by-pass the flaps, feed it more air and more fuel and get a compatible tune. The last part is the ONLY reason I miss carbs... increase the air, change the pilot jet, raise the needle, improve the slide spring, increase the main jet, increase the air, fine tune by reading the plugs and call it a day!
The Hattech Sidepipes are not a muffler swap. They are larger diameter, much shorter, no cats and no flapper valve (they do ship with plugs to spoof the ECU so that you don’t get any error codes). They are “off road — exhibition use only.” Although, like I said, not loud enough to draw any unwanted attention. So I suspect that the motor may be running outside of, or at the ragged edge of the ECU’s ability to adjust. Either way, Bren tunes radically improve BMW performance even if you don’t change a thing. That’s experience talking. So it’s off to Massachusetts with my ride.
I know the pipes you're talking now...yep you probably need a tune! And regarding Bren tunes...I've never used them and will check them out. For FI tunes I've relied almost exclusively on Dynojet products, and some Rexxer. And yes, my experience is that any OEM bike these days, even without any front to back changes will run better and cooler with a decent tune.
