| Author | Message | ||
     Fastxb12r |
I am building a few exhausts and am having a few questions.  I already have the elbow down packed so thats not the issue.  I am running the 2" elbow and am thinking for back pressure to either and or use a smaller diameter pipe like 1.5" for a couple inches then after the Y towards the rear back up to 2" on the dual exits.I have also found some small cherry bomb style mufflers much like the D&D ones.I would rather use the straight pipes but dont want to damage the bike. I currently have a race pipe,race ecm,K&N,open inner air box,open outer box,breather reroute. I am wondering what this could damage if I was to do the straight pipe but mind you I am going to step down in pipe size for back pressure. I dont care about power lose as I rode it with open header and I am telling you the bike never pulled harder and faster.I also noticed it didnt stink of fuel like when I had on the race pipe. I know people hate the straight pipes but I like having obnoxiously loud pipes to help the white hairs hear me.Plus I like how harley V-twins sound..... So if you hate it or think its stupid but dont have any REAL input keep it to yourself.please  | ||
| Glitch |
Check out the KV. http://www.badweatherbikers.com/buell/messages/384 2/3842.html?1244685148 There's some excellent stuff there, written by true exhaust professionals. You may have to look a little bit, but trust me, it's worth your while. Once you've perused the KV, come back here and tell me the myth that is "back pressure" is there such an animal? If there is, what is it, and how does it affect power? If there's not, what is it that is mistaken for the term? | ||
| Fastxb12r |
Thats the problem I looked at over 100 threads and I only found mostly people saying how dumb open pipes where when someone asked a question about it. Thats the only reason I am posting here. | ||
| Augustus74 |
I think I heard the smaller HD motors (883/1200) like 1 3/4" open pipes. Not sure about the length, maybe 21-23"??? Gotta look around. What bike are they going on and I want pics and sound clips!  | ||
| Pogue_mahone |
not sure about back pressure,but free open exhaust has pros and cons,and semi restricted does too and i mean as it pertains to the way the engine makes power. so i'll read and watch this thread | ||
| Jakecheez |
i have staight open headers on mine and ive been worried about the back pressure isse, too! the one bit of good advise/bad news that i've got is from an HD service manager. he told me that when you rev it up close to red line and let off fast, the air flow can reverse some and may cause the motor to "hick-up". If the motor stutters a little, then it can cause the piston and the valve to collide, causing the valve to bend. a bend results in a break short after. a break results in catostrophic damage to the motor!!! ouch- the one way to prevent this is to get a tuner (like a pilot command or somthing similar) and map it out to match the exhaust. the problem with a custom exhaust is that finding the map spec is nearly impossible. *not sure if this is any help, but I just got this info today, so I thought id pass it on while it was still fresh.... goodluck! | ||
| Glitch |
Do a search of Knowledge Vault Search user name Aaron Pay attention to header and muffler posts It may be a bit to wade through But like I said, it'll be well worth your while Could someone please explain this "back pressure" thing to me! | ||
| Zatco81 |
When I build mine I looked at a lot of different homemade mufflers. A lot of guys with fully gutted stock cans would complain about loss of power down low due to the lack of backpressure and the free flowing design. I welded chambers in mine with a straight pipe in the middle and noticed an increase in power all across the rev range. My homemade muffler and chopped airbox deffinately pulls harder than stock as read by the butt dyno. And I think it sounds killer too... Mine: (Message edited by zatco81 on June 11, 2009) | ||
| Zatco81 |
SOME READING. http://www.uucmotorwerks.com/html_product/sue462/b ackpressuretorquemyth.htm http://www.thumpertalk.com/forum/showthread.php?t= 659727 http://my.prostreetonline.com/forums/archive/index .php?t-1639.htm | ||
| Andymnelson |
ah the old backpressure is good myth. here's some facts about exhaust systems: - the point of an exhaust system is to quickly and efficiently evacuate exhaust gases - backpressure is not necessary to get the most power out of an engine, but may be necessary to getting the most power out of an otherwise stock engine because the fueling system often can not keep up - burned valves do not happen because of a lack of backpressure, they happen because of a too-lean condition - larger, nore open pipes do NOT equal less backpressure because a smaller pipe will carry the exhaust out at a higher velocity (think of water through a pipe- the same amount of water through a large pipe flows slower than when forced through a small pipe) - the trick is finding the gentle balance in between, where velocity and flow are maximized, but free enough that there is no restriction - with more exhaust flow must come more fuel and air flow - without flow meters and lots of bench testing and software modeling, the only other way to find that balance is LOTS of trial and error moral of the story: backpressure is bad! but our motors were not designed to have no backpressure- the fuel system can't inject fuel fast enough, and the throttle body isn't large enough to flow enough air. the system was designed with a certain amount of backpressure in mind. so eliminating backpressure would require redesigning the motor if you want it run at optimum. oh, and my factory designed race pipe, ecm and filter all function together fantastically. | ||
| Pogue_mahone |
i guess the obvious is for the home made exhaust is to not make it too free and open,and no weird restrictions either. | ||
| Andymnelson |
Jake- I would disregard anything and everything that your mechanic says if he suggest this: "the one way to prevent this is to get a tuner (like a pilot command or somthing similar)" Those tuners do not work on our bikes, and anyone worth touching your bike will know that. They make changes which the ECM compensates for eventually, negating your new tuner. Custom mapping through software that modifies your ECM is the only way to go. I assume you meant Power Commander? Those guys got sued and no longer sell a unit for our bikes. Hhhmmm, I wonder why?  | ||
| 1_mike |
If you are building an all out race bike...road race, drag race or for Bonneville...a NO restriction system will HELP...return the most power. BUT you have to tune it properly. If you are building a street bike/muffler, then some amount of restriction is a good thing. It's actually more than most realize, a fine line between power, driveability and sound. Doing one myself (XB12). Hope to be done in a week or so. Mike | ||
| Fastxb12r |
Augustus74 its going on the XB12R. I am wondering since my motor really stunk of raw fuel with a race ecm,race exhaust and all the above in the first post. Wouldnt it mean its running to rich and to give it more of a flow through pipe would be better? I also am wondering since the bike ran so strong and smooth with wide open headers wouldnt putting on 2" pipes just make it more like having a muffler. Just for the people here I plan on taking fly by videos this weekend with open pipes VS. the pipe I will build....That is if I get it fabbed and welded this weekend. | ||
| Augustus74 |
If your worried about backpressure with open headers, you might want to look at something like "torque cones". Small,short tube thingy that goes in your pipe right after the head to create a little back pressure and save your valves. I think they increase the torque too (hence the name).  | ||
| Tonskey |
WHERE is a good place to get your bike tuned i have an 07 xb9sx with a force pipe and would like to get if tuned who can i trust to touch my bike by the way I'm in missouri???? | ||
| Fastxb12r |
WHERE is a good place to get your bike tuned i have an 07 xb9sx with a force pipe and would like to get if tuned who can i trust to touch my bike by the way I'm in missouri???? Im in florida so I dont know but I would find a Good/Reputable v-twin hotrod dyno shop if you dont have a friend who can help with the ecm tune.  I would post a separate thread and ask maybe someone in the area can help.} If your worried about backpressure with open headers, you might want to look at something like "torque cones". I had the understanding that they only work when you put them directly in the header inlet by the heads.Plus I dont feel like rotating the motor. | ||
| Fastxb12r |
I got the welder dialed in and will be welding up the pipes tomorrow. | ||
| Augustus74 |
http://www.youtube.com/watch?v=0-BC9ry80Ps&feature =related Not mine, don't know anything about it. | ||
| Zatco81 |
What the hell was that?  | ||
| Augustus74 |
OP had a thread looking for pics of such a set-up. Don't make fun, you can barely hear your bike in your video!!! LOL Rev it up a little higher next time or do a drive by please, i am very interested in doing a car muffler exhaust. | ||
| Fastxb12r |
I think it was a S1 with a custom pipe similar to a D&D type and a XB swingarm. Thanks for the link didnt get to finish the pipe due to waiting a week for the Y pipe to do the dual outs. I did however get videos of the bike with the elbow I made and will post them later. | ||
| Fastxb12r |
I got the videos up its the buell with just header and the elbow I welded up...   (Message edited by fastxb12r on June 14, 2009) (Message edited by fastxb12r on June 24, 2009) | ||
| Augustus74 |
From the bottom up: pic 2 looks like the elbow is angled up not straight? Doesn't sound nearly as loud as I thought it would? Must be different in person. Maybe a video at idle revving it up? Oh, your girl(whoever)like most, doesn't understand why guys like loud things, and she wants a new camera, LOL. | ||
| Fastxb12r |
funny thing is its a brand new sony with a built in 320GIG harddrive camcorder....She just doesent know how to use it.  Its not as loud as you would think open headers are loud but as soon as I put the elbow on it quieted up quite a bit. I have it angled up a little but when I put the straight section on I will fix that by cutting it.I am just waiting on a "Y" to moc everything up and tack weld it all thats when ill cut it. | ||
| Joesbuell |
http://www.youtube.com/watch?v=0-BC9ry80Ps&feature =related Not mine, don't know anything about it. That would be my custom S3T here's the latest vid with the reverse cone pipe. http://www.youtube.com/watch?v=WG03lX5QTwE | ||
| Cryptic1911 |
sounds cool I loled at the "GOD I HATE THIS CAMERA!! UGHHHHHHH" | ||
| Zatco81 |
I wasn't making fun...I was really asking "What the hell is that?" Now that I know...It's badass! Nice bike. Oh and if you thought the sound was bad on my vid you should have heard the one I took with my phone. Thats what you get from a digital camera. If my 4 year old will tell me what she did with the charger to my camcorder...I'll take another one. (Message edited by zatco81 on June 14, 2009) | ||
| Augustus74 |
Sorry, technology and people like Fast spoil me with 7 videos!!! I like to hear "fly-bys".  | ||
| Fastxb12r |
Heres what im looking at making to do the exhaust from my elbow back.The measurements will be perfect and the 2 Y's welded together sjould give just enough resistance to work right. Thoughts....OH also its all 409 stainless steel      |
