| Author | Message | ||
     Jmkushla |
just wanted to see if some straight pipes are possible. wanted a set that followed the same path as stock exhaust then slightly split on either side of rear tire | ||
| Froggy |
Yep it can be done, despite how loud and undesirable the results will be. | ||
| Fast1075 |
Sure if you don't care how bad it will run...somebody will build you a set I'm sure. | ||
| Fresnobuell |
Get a D&D, which is pretty close to straight thru. You will be sorry for more reasons than one. | ||
| D_adams |
This is probably the closest you'll find. Not quite straight pipes, but close. BTW, does this make my butt look big?  (Message edited by d_adams on February 14, 2011) | ||
| Hybridmomentspass |
damn you Dean for posting that exhaust porn | ||
| Froggy |
Dean, just make a new version without the cans, and sell it to this guy  | ||
| Jdugger |
I like a nice tailpipe. | ||
| 99buellx1 |
....anything is possible. | ||
| Ljm |
Guy up here in AK has one with straight pipes. They are duals, rather than being a two into one. My older 1125 had a d & d when I bought it and I think the straight pipes are not quite as loud. Could be where they exit (off right side, straight down) but still painfully loud. Much more than aftermarket cans I've heard. LJM | ||
| Forerunner |
I ran my 1125 for just a few seconds at idle when I had the muffler off before installing the FMF. I ran it for only a few seconds because that's all I could handle. Well beyond my limit of tolerance and I typically like loud. YMMV, Nels | ||
| Ausxb |
A mate had this made locally pretty much straight through..... f#####g loud! and produced fueling issues, big imbalance F&R...wasn't prepared to get it tuned no one local who could do it and wasn't prepared to DIY    | ||
| Fresnobuell |
These bikes are loud. i have seen a couple different guys around here on XBs without a muffler at all--just the bare headers--and I think my Barker is almost as loud as those pipeless XBs. Maybe not quite. | ||
| Duphuckincati |
JM, what is the attraction for you to straight pipes? | ||
| Zac4mac |
LOUD Fire out the back on decel. Just my WAG | ||
| Slaughter |
Possible? Yes. Job security for your dyno tuner. You guys will be starting from scratch and at the end you will make less power and more noise. WAIT JUST ONE MINUTE!! Less power, more noise??? You could just buy a Harley! (Message edited by slaughter on February 15, 2011) | ||
| Rex |
has anyone tried to make 4 pipes? 1 pipe for each outlet on the head? might be kind of cool looking...do a lot of twisting they around and then back in to two and back to four outlets? | ||
| Dman |
"WAIT JUST ONE MINUTE!! Less power, more noise??? You could just buy a Harley!" Now I don't care who you are, that's funny. | ||
| 1_mike |
Not necessarily less power. If the stock header is all that used...yea, bad idea power wise. But if some homework is done and tube diameters and lengths are scienced out...while still horribly noisy, could be ok power wise. It would just take doing a lot of homework to design the "correct" open header for his application (read that rpm). It would most probably also require a third collector, for a single outlet. Mike | ||
| Forerunner |
I would guess that properly sized tubes and properly tuned fueling would achieve very high power outputs and most likely at very high RPM. Racecars(spelled the same backwards or forwards) and racebikes that I've seen don't run mufflers and are trying to extract every last ounce of power. The ones that do run mufflers are usually doing so to meet track db requirements. Nels | ||
| Duphuckincati |
I gotta say, if I came upon someone riding an 1125 with straight pipes on the street one word would enter my mind and it would be butthole. (that's the version Blake will allow) I'm sure I'm not the only one. | ||
| Forerunner |
I will constrain my comments on the subject of straight pipes or open headers to 'off road use only.' Nels | ||
| Dannybuell |
on my 96 s1 I have a D&D. several years ago as I was accelerating away from a stop light the bike fell flat on its face, power dropped off so quickly I actually lunged forward. Things got really loud. I stopped the bike and noticed the back half of the muffler had blown off. I went back and retrieved the rear cap. I went to my friends shop and welded the thing closed. motorcycles need back pressure to run properly, how much IDK. | ||
| Forerunner |
motorcycles need back pressure to run properly Old wive's tale. Thanks to D_adams for the info below: Backpressure: The myth and why it's wrong. I. Introduction One of the most misunderstood concepts in exhaust theory is backpressure. People love to talk about backpressure on message boards with no real understanding of what it is and what it's consequences are. I'm sure many of you have heard or read the phrase "Engines need backpressure" when discussing exhaust upgrades. That phrase is in fact completely inaccurate and a wholly misguided notion. II. Some basic exhaust theory Your exhaust system is designed to evacuate gases from the combustion chamber quickly and efficently. Exhaust gases are not produced in a smooth stream; exhaust gases originate in pulses. A 4 cylinder motor will have 4 distinct pulses per complete engine cycle, a 6 cylinder has 6 pules and so on. The more pulses that are produced, the more continuous the exhaust flow. Backpressure can be loosely defined as the resistance to positive flow - in this case, the resistance to positive flow of the exhaust stream. III. Backpressure and velocity Some people operate under the misguided notion that wider pipes are more effective at clearing the combustion chamber than narrower pipes. It's not hard to see how this misconception is appealing - wider pipes have the capability to flow more than narrower pipes. So if they have the ability to flow more, why isn't "wider is better" a good rule of thumb for exhaust upgrading? In a word - VELOCITY. I'm sure that all of you have at one time used a garden hose w/o a spray nozzle on it. If you let the water just run unrestricted out of the house it flows at a rather slow rate. However, if you take your finger and cover part of the opening, the water will flow out at a much much faster rate. The astute exhaust designer knows that you must balance flow capacity with velocity. You want the exhaust gases to exit the chamber and speed along at the highest velocity possible - you want a FAST exhaust stream. If you have two exhaust pulses of equal volume, one in a 2" pipe and one in a 3" pipe, the pulse in the 2" pipe will be traveling considerably FASTER than the pulse in the 3" pipe. While it is true that the narrower the pipe, the higher the velocity of the exiting gases, you want make sure the pipe is wide enough so that there is as little backpressure as possible while maintaining suitable exhaust gas velocity. Backpressure in it's most extreme form can lead to reversion of the exhaust stream - that is to say the exhaust flows backwards, which is not good. The trick is to have a pipe that that is as narrow as possible while having as close to zero backpressure as possible at the RPM range you want your power band to be located at. Exhaust pipe diameters are best suited to a particular RPM range. A smaller pipe diameter will produce higher exhaust velocities at a lower RPM but create unacceptably high amounts of backpressure at high rpm. Thus if your powerband is located 2-3000 RPM you'd want a narrower pipe than if your powerband is located at 8-9000RPM. Many engineers try to work around the RPM specific nature of pipe diameters by using setups that are capable of creating a similar effect as a change in pipe diameter on the fly. The most advanced is Ferrari's which consists of two exhaust paths after the header - at low RPM only one path is open to maintain exhaust velocity, but as RPM climbs and exhaust volume increases, the second path is opened to curb backpressure - since there is greater exhaust volume there is no loss in flow velocity. BMW and Nissan use a simpler and less effective method - there is a single exhaust path to the muffler; the muffler has two paths; one path is closed at low RPM but both are open at high RPM. IV. So how did this myth come to be? I often wonder how the myth "Engines need backpressure" came to be. Mostly I believe it is a misunderstanding of what is going on with the exhaust stream as pipe diameters change. For instance, someone with a civic decides he's going to uprade his exhaust with a 3" diameter piping. Once it's installed the owner notices that he seems to have lost a good bit of power throughout the powerband. He makes the connections in the following manner: "My wider exhaust eliminated all backpressure but I lost power, therefore the motor must need some backpressure in order to make power." What he did not realize is that he killed off all his flow velocity by using such a ridiculously wide pipe. It would have been possible for him to achieve close to zero backpressure with a much narrower pipe - in that way he would not have lost all his flow velocity. V. So why is exhaust velocity so important? The faster an exhaust pulse moves, the better it can scavenge out all of the spent gasses during valve overlap. The guiding principles of exhaust pulse scavenging are a bit beyond the scope of this doc but the general idea is a fast moving pulse creates a low pressure area behind it. This low pressure area acts as a vacuum and draws along the air behind it. A similar example would be a vehicle traveling at a high rate of speed on a dusty road. There is a low pressure area immediately behind the moving vehicle - dust particles get sucked into this low pressure area causing it to collect on the back of the vehicle. This effect is most noticeable on vans and hatchbacks which tend to create large trailing low pressure areas - giving rise to the numerous "wash me please" messages written in the thickly collected dust on the rear door(s). | ||
| Zac4mac |
Good stuff there, helps to explain why a 2-1 makes more power than a 2-2. Velocity and combustion chamber evacuation... Rocket science anyone? Another observation - Dean makes the RT-4 a beautiful 2-1-2system that makes power and sounds better than ANY other exhaust, IMO. Free Spirits makes a 2-2 system that LOOKS awesome. Sounds like shit tho, don't know how it compares to my Drummer or Dean's cans, they didn't send one for the American Sport Bike Exhaust shoot-out. (Message edited by zac4mac on February 15, 2011) | ||
| Dannybuell |
Flow velocity is good but don't call it back pressure .... | ||
| Blake |
Never heard the velocity explanation before for exhaust, but it makes sense as I know the same is true for intake. Energy being critical and proportional to velocity squared, it's easy to see why velocity can govern over flow (pressure). Always heard that exhaust tract design is most sensitive to pressure wave reflections, the idea being to put a negative wave at the exhaust port during the intake and exhaust valve overlap event in order to assist scavenging. Any discontinuity like a collector or any change in flow path diameter will cause a reflected wave. The more you have, the weaker they get. The weaker they get, the less effective at helping to pull-into the combustion chamber (scavenge) additional air/fuel charge during the overlap event. So you want just enough discontinuities that are placed appropriately downstream to cover the desired power-band of the bike. A straight pipe has just one reflection point, at the end of the pipe, thus a narrow power-band. Check out Wes and Pammy's stepped straight pipes for the optimum power-generating exhaust tract configuration. The megaphone (expanding chamber) idea is neat too, it creates a softer wider range of reflection. See MotoGP. Seems to be analogous in some respects to RF wave device tuning for wider bandwidth. | ||
| Kds1 |
I have to do this, I can't help it...backpressure is present in exhaust flow, it is needed however to much is restrictive, exhaust flow is not continuous outward, turns aroung and goes back to the port the same number of times it goes out....scavenge is great, just like anything else in life, too much is wasteful, just enough is good...I totally agree that some people talk about backpressure that really don't have a clue to what is happening, some people talk about backpressure, velocity, anti-reversion and really do know what they are talking about....efficiency makes more useable power over a broader range, straight pipe with a tuned specific length will make the most power for the rpm band that the math was used to design for....if the exhaust only has to flow 80% of the intake, if you need such a large opening to flow out of and all this scavenge, why not put bigger exhaust valves and ports than the intake....I love straight pipes on a blown nitro engine, doesn't seem to matter what is on those!!!! Kevin www.kdfab.com | ||
| Carbonbigfoot |
Good to hear you chime in, Kevin! For the rest of you, this guy knows a thing or two about exhausts.... R | ||
| Dannybuell |
the D&D on my S1 is a megaphone, it apparently lost velocity and crapped out. the Barker on my CR has the 1" quiet core it does not rev as fast, the good part is my ears are no longer ringing. a blown nitro engine is WOT not much else. | ||
| Fresnobuell |
there is a single exhaust path to the muffler; the muffler has two paths; one path is closed at low RPM but both are open at high RPM. Okay rookie question here--is this the reason for the solenoid in the XB12 exhaust? | ||
| D_adams |
Yes. Long tube exhaust for low rpm operation, short tube for higher rpm. I don't know where the switch point is, but I'd guess somewhere around 4k rpm or so. Tuned length pipes for different ranges, kind of a mix to get the best of both. | ||
| Fresnobuell |
Wonder why they deemed this beneficial for the 12 but not the 9? | ||
| Zacks |
Volume - not as in noise - would be my guess. Bigger cylinders would push more air. |
