| Author | Message | ||
     Riclyd |
One thing I have learned about motors is that the exhaust pipes should be at equal length so each cylinder gets equal amount of resistance. And there is even equal length header pipes as after marked parts, why is not that standard for the XB's? And what difference does it make? | ||
| Glitch |
45o V And the way the bike fires. Equal length would help an equal 90o engine. For a more detailed explanation look in the knowledge vault. | ||
| M1combat |
You want them equal if they aren't a 2 into 1 system. If they are, you want them unequal. | ||
| Glitch |
yep | ||
| Djkaplan |
Why would you want unequal length primaries in a 2 into 1 system? | ||
| Diablobrian |
it has to do with timing exhaust pulses to help draw more air/fuel into the cylinder. beyond that it gets really complicated. | ||
| Djkaplan |
Primary length and diameter have a direct bearing on resonance caused by pressure waves in the exhuast. Why would you want this resonance to occur at different rpms in each cylinder? It seems like Buell engineers go to great lengths to keep the primaries as close to equal length as possible. What am I missing here? Is it the firing pulses entering the collector at uneven intervals? Are the primary pipes not actually equal length? They sure look equal length on my race header. | ||
| Diablobrian |
our motors do not have an even firing pattern. thus the potato potato sound. there has to be a compromise to get the most out of it. The uneven lengths are the result. There is a lot of variance from the different companies because they optimize for different rpms. Some race headers are equal length depending on what their research has shown them. I would imagine this is because of the frequency of the pulses at high rpms, where the pipe is targeted. A street pipe on the other hand will be tuned for more mid- range. There is a fair bit of art as well as science, and even packaging involved in the selection of length and diameter of the headers. It sounds like you have a pretty good handle on the science behind it. (Message edited by diablobrian on February 24, 2006) | ||
| Blake |
Ducati uses unequal length header pipes on their 999. | ||
| M1combat |
You're trying to time the pulses at the collector so that the negative wave from one cylinder helps the other cylinder to scavenge the spent mixture. Because we have a single crank journal and both pistons go up and down 45 degrees apart from each other the pipes need to be different lengths to get the pulse where it needs to be when it needs to be at the RPM you want it all to come together. If you run a 2 to 2 sytem though, then you do want to have the same volume in each pipe (aside from a variance that you may build into the pipes to account for the extra heat from the rear cyl...). | ||
| Djkaplan |
"Ducati uses unequal length header pipes on their 999." But the primary pipes differ in diameters too. The net effect is resonance occuring at the same rpm range for both cyinders. This article touches on this very subject... http://www.sportrider.com/bikes/2003/146_03_ducati_999/ "Optimally, exhaust pipes should be equal length. The Ducati 999 solves this in a unique way by varying the diameters of the exhaust pipes to simulate equal length pipes. The front pipe diameter increases from 45 to 55 mm compared to the constant 45 mm diameter of the rear pipe. I don't think the difference in primary length is used as a tuning parameter, it's more of a packaging issue that had to be worked around with some creative thinking. I've looked at just about every header, stock and aftermarket, for Buells and every one of them seems to have equal length primaries. If they are unequal length, it can't be by more than an inch (or less). It seems if there was some benefit to unequal length, we'd see it in the aftermarket. Could anyone point me towards a currently available exhaust (for Buells or otherwise) that uses unequal length primaries as a design feature? | ||
| Djkaplan |
This article touches on the subject of "should header pipes be equal", but doesn't quite answer the question. http://www.rbracing-rsr.com/exhausttech.htm Still looking... | ||
| Cycleaddict |
how about curves, bends, etc . a 90' bend is roughly 4 x more restrictive than an equal length of straight pipe. | ||
| Riclyd |
As I understand, these pipes will not give our v-twin any positive effects?  | ||
| Donutclub |
When comparing the length of the header pipes, I'd think it would be more of an energy loss comparison versus a length comparison. Hydraulic losses consist of the following: friction, entrance, exit, and bends. | ||
| Anonymous |
Tons of research have gone into it, and I'd venture to say Buell/H-D know more about 45 degree V-twins than anyone on the planet. Unequal length pipes give more power on a 2 into 1 system. It is a crucial part of making a collector system work at it's best on one of these engines, and it takes very sophisticated computer modeling tools to get the design right. It is indeed as Diablo first said, that a 2 into 1 system works with pressure pulses which are influenced by the oppositie cylinder. Because to unequal firing cylinder timings occur, the pulses get fired back up the pipes at unequal times. Therefore to get equal effect on each cylinder, the pipes have to have an offset to compensate for the unequal pulse timing. That's why the XB street bikes have them, as does the XBRR. Don't assume that because someone builds a non-street legal noisy pipe than has equal length pipes and it makes more power than a street pipe, that the pipes are the reason. It just ain't so. On separate exhausts for each cylinder, equal length is usually correct for ultimate peak power, although sometimes unequal lengths are used to broaden the powerband at the expense of peak power. | ||
| Djkaplan |
"Is it the firing pulses entering the collector at uneven intervals? Are the primary pipes not actually equal length?" Thanks for answering my questions, whoever you are. | ||
| Blake |
Why DJ, that is "Anony" our good friend and big hairy ball of knowledge concerning all things Buell.  | ||
| Buelldyno_guy |
One of my biggest heart aches are those who bring a bike for me to Dyno with a great engine and a lousy exhaust. Yes it's always loud and way too often it doesn't work well. When I am done tuning and they are not happy with the numbers, I have always tried to tell them, "You can't blow out more than you can suck in and you can't suck in more than you can blow out." So from a tuners point of view My Hat's off to those of you who have designed a good flowing and performing system. ... Terry | ||
| Jimincalif |
Say you have an engine with two cylinders firing exactly opposite each other, generally either a parallel twin or opposed twin ("Boxer") motor. You can set up a situation where each cylinder's exhaust flow travels down the pipe, gets JUST past the 2-into-1 merger point and then the other exhaust cycle starts. In this event the pulse from the other cylinder now just past the merge sucks THIS pulse out faster than it would normally flow. The pipe lengths control this "timing" of suction pulses. In the case of our hog motors, we can really only do this "halfway". We can suck one cylinder's pulse with the other. Think about how our crank, rods and pistons are laid out and you'll get it. This is why our two pipes are of different lengths, or can be: only one of the two lengths really matters related to "timing". | ||
| Riclyd |
I watch the OCC program on the Discovery chanel and it don't seem to me that they care much of the pipe length when they build their choppers, and they should be professionals. | ||
| Jens |
The potato-potato-potato timing is not equal to rice-rice-rice... -or other engineconcepts with a constant angular ignition spacing. In times of wave analyzing many golden rules get lost. I believe in the interference point for roadexhausts, but thats experience and meaning not science. Have a look at the Moto GP Bikes how unequal their headers are today, or look at Kawasaki Moto GP bike they use straightouts to get rid of the torque (-; Modern sequentiell working engine management systems compensate a lot. Jens | ||
| Imonabuss |
OCC professionals!!!!!ROTFL  | ||
| Lenny |
Two into one is the way to go for making serious street power.The area under the horsepower and torque curves defines the "power" the engine produces.The more area that is under the curve, the better the power. Two into one use the exhaust of one cylinder to pull out the next cylinder exhaust. Thats just my two cent | ||
| Blake |
Doooood! OCC cares for nothing but the looks of their two wheeled creations as far as I can tell. | ||
| Kdan |
OCC cares for nothing but the looks of their two wheeled creations as far as I can tell. How fast you wanna go on one of those things anyway? I think volume is more important, you want people to hear you coming, since you can't stop. | ||
| Road_thing |
Well, the guys at OCC do build bikes and they get paid for it, so I suppose that does make them "professionals", grammatically speaking. But their bikes don't interest me. What does that make me? Un-professional? rt ..and he throws out a slow, hanging curve that just clips the plate, high and outside... | ||
| Bomber |
Thang -- I believe that makes you an amatuer -- one who is involved for the love of the thing, not the dough (goodness knows your motorcycle cash flow, like mine, is pretty much one-way ;-} ) OCC may be capable of building good bikes -- the stuff they do for their corporate sponsors and TV shows does not demonstate that, sadly -- |
