| Author | Message | ||
     Aydenxb9 |
Did anyone else read the article on the ZX-6R in the new Cycle World? It has a "servo-operated exhaust valve" in the muffler. Claim it controls the pressure waves inside the exhaust system for enhanced low- and midrange power characteristics. I've heard that some where before, right?  | ||
| Blackbelt  |
i am not sure... it sounds familiar.. in fact i think we saw a press release on that sometime like i think august 2003.. but i am not too sure...  | ||
| Reepicheep  |
Fair is fair, I think Yamaha did that a while back with their ExUp system. Buell just did it better  | ||
| Tripper  |
I think Yamaha has had the EXUP system (valve in the collector not the muffler, but similar effect)since, guessing here, 1990? All the Japanese sportbikes have used similar devices. On the other hand, I was reading the review of the MT-01 and as I looked at the pics and read the reviewer's impressions, I kept seeing my S1. I think the MT-01 is an interesting bike, but has all the appeals of the S1. | ||
| Lpowel02  |
i think honda did a similar variable airbox and exhaust system on the CBR a few years ago too... edit: called HTEV - it was on the 2000 CBR929RR (Message edited by lpowel02 on February 02, 2005) | ||
| Tripper |
Hi Bill. Should'nt you be working? | ||
| Dropnstyle |
yea my 929 had one but it wasnt in the muffler, it was before the muffler right where the header went from 4 to 1, it kinda was the collecter. kinda hard to explain easy to see in person. anyways it worked. riddin many liter bikes and the 929 and 954 have great low range compared to others. of coarse the buell kills em all | ||
| BadS1  |
I had a FZR 1000 and the exup valve was before the muffler.Piece of crap it was to.It rusted shut it rusted closed and the cable snapped once.Went through 2 systems and one cable in 2 1/2 years.Piped it after that.My 12 is piped now.I for see the same happening after time to those as well.Maybe not the valve but the cable will need extra attention to stop corrosion. | ||
| Nedwreck  |
The Yamaha YZ350 had YPVS in the eighties. Bob | ||
| Just_ziptab |
The "valve in exhaust" system was used in the early 70's to win the Daytona 200. At that time, is was something like a 4 barrel carb throttle base, grafted in line on the header collector. I can't remember how it was controlled.  | ||
| Anonymous |
The biggest difference with the Buell are these: It actually changes the gas path, instead of just changing back pressure like the competion, and even more importantly, it is actuated by the ECU under a number of different scenarios and time schedules depending on the ECU sensor inputs. The competiton used stytems that basically were actuated at a certain RPM. The difference in effect on performance between these two different approaches is substantial, and Buell has by far the more advanced one. | ||
| Loki  |
A strange thought just came to mind. Not about this thread in particular either. Why do I feel like I am having a Python experience. That would be a Monty P experience! | ||
| Littlebuggles  |
"I want an shrubbery" ?  | ||
| Doughnut  |
"African or European?"  | ||
| Littlebuggles |
Ah, I'm a little slow but I usually catch on. Good cop, have a doughnut. I'll go back to lurking now...  | ||
| Doughnut |
More to the story, but you got half of it. | ||
| Newfie_buell  |
So what effect does it have when people remove the stock pipe? | ||
| Littlebuggles |
Just taking a stab but I'd say the same thing as piping most bikes - you end up with a trade off, lose low end power for HP (free breathing pipe) or lose HP for low end (generally more back pressure). Off subject but it works that same (the end result I mean) with cams and lift duration doesn't it? The HP vs Torque thing... Please educate me if I'm wrong. -Mike | ||
| Djkaplan  |
I think if you disabled the valve on a stock XB, you'd wind up with a big hole in the powerband. | ||
| Blake |
More back pressure never produces more power. More back pressure always diminishes power. | ||
| M1combat  |
"I think if you disabled the valve on a stock XB, you'd wind up with a big hole in the powerband" There are Dyno's on the ?hillbilly? site that prove this. Both with the exhaust stuck open and closed, with and w/o their FAST intake system as I recall. | ||
| Anonymous |
Yes, that's because neither path of the Buell system has any back pressure to speak of, just different noise attenuation and tuned length. Take the valve off and you lose the path that gives low end torque. | ||
| Blublak  |
Nie! | ||
| Littlebuggles |
Blake, Maybe I should check the KV for the answer then but my bike seems to have less down low grunt since I swapped my E-Series pipe for a Vance. Don't disk pipes tune back preasure/flow for best performance? | ||
| Crw  |
Don't think back pressure...think acoustics. | ||
| Just_ziptab |
I installed the Buell race muffler(no valve), off of my ECM'd 9R ,on to my stock 12R. I didn't notice any changes ,except a pleasant sound. A D&D went on the 9R.......neart "loud" now. | ||
| Blake |
Back pressure is a characteristic of the flowability of the system. Restricting flow creates higher pressure losses between exhaust port and tailpipe and is never helpful as far as power output is concerned. As mentioned above by others, the performance gains of any 4-stroke exhaust system come from eliminating restrictions to flow and in designing the system to put a negative pressure wave (suction) at the open exhaust port rather than a positive pressure wave. So like CRW says, it isn't backpressure; it is more akin to acoustics in the form of reflected pressure waves. Just don't confuse the acoustic cancelling of the muffler with the pressure pulse design of the exhaust tract. They are two different things. Of course the acoustic design of the muffler also affects the pressure pulse reflecting characteristics of the exhaust tract. To answer your question though, no, the tunable disk type mufflers allow one to tune the pressure wave reflection performance of the system, not so much the back pressure. Back pressure, meaning restriction to flow, is never beneficial for engine performance. The only instance I can recall where back pressure was a good thing was way back when valve seats and valves would burn if the hot exhaust gasses were allowed to fly out the exhaust port unimpeded. In those cases, the backpressure kept the valves and seats from burning; it did so by impeding performance. Nowadays, the valves and seats are made from materials that are largely impervious to being burned up, thus there is no need for any backpressure inducing exhaust tract designs. The whole idea that backpressure helps performance is a long tired myth. Back pressure hurts performance. The tuned exhaust tract that puts a suction pulse at the open exhaust port during the open intake/exhaust overlap event will aid cylinder filling, while the converse will hinder cylinder filling (having a pressure pulse arrive at the open exhaust port during the open intake/exhaust overlap event). This is why different cams with different overlap between intake/exhaust will often require a different exhaust tract design for optimum performance. This is the reason for the valve in the XB12 muffler, to put the negative (suction) pressure pulse/wave at the exhaust port at the opportune moment. As engine speed (RPM) changes, the optimum exhaust tract configuration/geometry changes as well. The optimum solution would probably be a sliding trombone type tailpipe that changed length according to engine speed. In general, lower engine speeds require longer length exhaust tracts due to the longer time interval between exhaust pulses. I've seen animated illustrations of how a tuned exhaust tract functions. Do a google search and you'll find lots of pertinent info. Just be careful to look for 4-stroke information; the 2-stroke engine exhaust tract design is governed by other concerns completely foreign to that of a 4-stroke engine. Here's one informative link, http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm. Note particularly the section entitled "The Exhaust Pulse." |
