| Author | Message | ||
     Blackhat |
I've got alot of questions for the knowledgeable types out there. Sorry in advance if this one has already been beaten up before. The bike is a 2003 XB9R, completely stock 'cept for the K&N filter. I hear alot about exhaust back pressure vs. free flowing, the need for exhaust volume which is a challenge for Buells given the location and space provided for the muffler etc. I have the tools, mediocre welding skills, patience, and some cool ideas in either modifying my stock can, or designing and building one from scratch. Modifying the stock can is my 1st choice simply because it already fits. My dealer told me that Buell (or some rep) did an experiment by running cargo straps around the stock XB muffler, and hanging the bike upside down from the muffler. No proof, but just looking at the system leads me to believe it possible. So I don't really want to mess with that integrity of the bike. A simple, but incredible design. Why is back pressure important? Seriously I have no clue, except what is talked about here, like lack of dampens your lows and mids, and too much kills your highs. My simple train of thought, is that any back pressure puts more load on the engine to push, thereby sapping power. If someone could explain this at the 8th grade level, I'd appreciate it. What's the difference between exhaust volume, and back-pressure, and how do they work together? I think I understand about 50% of this one. Volume is the length of the system, and back pressure is the amount of restriction. Back in the 80s, I owned a beater '74 Vega that we dropped a 327 in. Built our own exhaust by mounting straight 2 3/4" pipe to the headers. To determine length, or "tune the exhaust" we would paint the straight pipe with cheap spray paint, run the motor and get it hot. Where the paint stopped burning off the pipe, we would cut it, then bend it here and there to fit, and dump out the side. This was an old school technique that was somewhat common where I was growing up, so I followed suit. This would be hard to do with a stock can. Does anyone know the ideal (happy medium) length of the XB9 exhaust? Will changing the length of the exhaust damage anything? I.E., ECM's normal function, backfiring through the intake etc? What is the diameter of the pipe inside the stock can? Type of metal? If I shortened the exhaust by re-routing the exhaust path using the stock internal muffler pipes, will that kill my necessary back pressure? Could this be offset by reducing to a smaller diameter pipe before the outlet, or will this cause alot of crackle and pop when I let off or downshift? Is there anything wrong with crackle and pop besides the noise? I will use the stock 03 XB9, 2 to 1 header. From there, what is generally the better setup, duel outlets like the XB Race muffler, or single? Once I've got everything welded in place (inside the can) I'll give the works a good treatment of Phosphoric Acid to kill any rust, and spray it with a light coat of paint, before closing up the can. Same treatment to the outside. I would like to use stainless piping on the inside to re-route the exhaust. I don't think it will work considering the tightness of space, and stainless steel's brittleness and poor bending/flairing qualities. What's the best alternative to stainless? Shit, this is long. I'll stop here for now. I've got more questions, but I'll wait. Any help is appreciated. I'll post a sketch of what I plan on doing when I get some time. Knowledge is Power! Blackhat | ||
| Kds1 |
Blackhat, 101 is everyone thinks bigger is better, but its not, it is only percieved as better because it looks as if it will flow better...first question is why would it need to be bigger,longer,shorter??? You have to first know what makes an internal combustion engine function? No need in having your head pipes bigger than your exhaust valve size...exhaust movement is not the problem in the pipe its usually the muffler...yes you need backpressure but a very little... its called progressive backpressure...well i'm getting tired of typing and my brain is going to explode...more later...KEVIN | ||
| Buckinfubba |
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| Gonen60 |
didn't i see that exhaust canister on FD engine 54 ? | ||
| Pilk |
hey guys you are beating a dead horse, do a search in the knowledge vault on the backpressure issue, Aaron lays it out very clearly. Pilk | ||
| Buckinfubba |
pilk beatin a dead horse is what keeps this place cookin  its been laid out a million times | ||
| Buckinfubba |
gonen oh yeah I forgot yes you did. that is a fir extinguisher all cut up and polished up | ||
| Gonen60 |
beatin a dead horse is what keeps this place cookin AINT THAT THE TRUTH, except not sure last time we talked about fire extinguisher exhaust cans, or side mounted exhaust cans, or building XB9S/Rs or the thousand other new topics..."nothing new under the sun? " ...bull shit !!! | ||
| Buckinfubba |
yeah I ain't sure we've seen fireextinguishers for exhaust cans. maybe that is new. I will post up something here a lil later that shows some fun facts about some stuff. It was on a race bike that the engine was about ready to fly apart but it gives you an Idea. or atleast I think it might | ||
| Buckinfubba |
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| Buckinfubba |
ok kev said this might help. This if you read the notes is on one of our race bikes now ofcourse the numbers don't show it but the engine is on its last leg. The race shop wanted to see how the drummer would work on this bike. well with 1350cc, xb12 headers and the drummer which was straight bolt on no fuel map change it was about 2 hp better than a double stepped header, equal lenghts, and a 3" collector. the fuel map was made for this set up and not the 12 headers with the drummer. what makes this signifigant is that with the drummer and 12 header it leaned the fuel ratio out to almost 18:1. so imagine what the difference would have been if they had changed the map for the drummer set up. Now kevin ask me to explain it and I have probably done it wrong so maybe he will do that tonight when he gets home. but smaller headers with a big voulme pipe worked better. so bigger ain't always better. I hope I didn't screw that up. damn that engine was ready to go boom | ||
| Kds1 |
Hey guys, Bubba finally got something technical right... Very well explained...KEVIN |
