VFRquig

Exactly how I felt. I was completely engrossed in your quest to make the viffer whole again and then to have it all end that way. Truely happy you are ok! Good luck with your next endeavors and include us on an of the cool BMW mods that are sure to arise!

Sweet- thanks for all the free knowledge. Now I just have to decide if the weight savings of going Cat-less will make my ride scary fast- lol One last thing- will the change in restriction have any negative effect on the bike? I assume the bulk of the exhaust restrict comes from the cat, not the stock pipes. I have fears that such a change may cause problems? Any comments?

I think it is all making sense now. So if I put on the new -old headers, and used the O2 sensors, I wouldn't really see much on the bike performance wise. My bike would just run closed loop at all TP and I might get a bit more sound from the stock cans? Correct? Sorry if I sound like a dumbass asking this many questions. I am just trying to squeeze as much bang-for-the-buck out of the silver bullet as possible.

Thanks HS. I was looking for a bit more ed-u-ma-ca-shun on how it actually worked in terms of various throttle situations so I appreciate the help. If I understand this correctly, the O2 sensors "tell" the system to richen/lean mixture as needed depending on the readings before and after the Cat. So my question is, if the Cat is not there (ie 99 header pipe) and the sensors are eliminated, does the bike run leaner, regardless of throttle state (steady, WOT) or does the bike run richer? What actually controls the fuel/air mixture on the bikes, other than the stock map and O2 sensors? It seems the removal of the Cat would decrease the restriction enough to require a change in the mixture (assuming factory exhaust and no PC III). So, to complete my ramblings, if I were to get 99 headers, with no aftermarket pipes and no PC III for my Vtec, would I notice any positive or negative performance changes (hp) or will it simply be enough to address surging problems for those unlucky owners that have them?

I asked a similar question on another recent thread and am impatiently waiting for a response Here it is again to add to Dave's question: If the 99 headers have no cat and the resistors are plugged into the O2s, what does that do to the FI without a PCIII? Does the bike run richer overall, but without the Cat produces more hp? If one were to simply run eliminators on a bike with a Cat and no PCIII, what would happen, assuming no aftermarket pipes? More hp / hurt performance / nothing? Inquiring minds want to know! I really know very little about the intricacies of the FI system and have learned a lot from some of our more technical folks at VFRD. As always, I appreciate the info!! Thanks.

HS is going the right direction with this, I believe. Going back to my Hardley days, the baffles were removed completely and replaced with a 1/4" bolt to provide sufficient backpressure- they still ran like crap, but boy were they load!!! :goofy: Ok, I digress, if you completely block off the end, you will have too much back- pressure and the bike will not run correctly. If you drill a whole in the end, you may improve this, but you may also induce a whistling noise that is annoying at best. What I have seen done that appears to work well is to crimp the leading edge of the baffle. This splits the exhaust airflow, some will go through the baffle end, some is redirected to the outside surface where it will enter the perforated section of the baffle. To do this, heat the baffle with the torch and bend the leading edge in to form more of a cone shape. Its kind of hard to explain without a pic, so think about it like this. Imagine what would happen if you squeezed the end of the baffle equally around its circumfrence (provided you were strong enough). It would taper down to a cone, which is what you want. Oh, I forgot the most important thing- AWESOME MOD!!! :beer: