It most certainly matters but again is going to be such a finite element in the tuning I wouldn’t go nuts with it. Factor in the length of the system between the merge and the beginning of the silencer and you’ll be right on par with where you need to be. Factoring in the silencer is going to require some fluid dynamics and factoring in the rapid expansion of the pulse within the volume of the silencer body.
I’ll post more on the tuned pipe theory later, and link you some ceramic packing as well.
The “silencer” is going to be all of about 6" long or how ever much I can fit under there. Idea is a 3" dia 16ga SS tube how ever long I can make it, lets call it 6", cut down the center. add in two, 1" or 2" X 6" strip of 16 ga flat bar between the 2 halves, making a 3"X4or5"X6" long oval tube. Cap the ends, send a 1.5" or 2" dia pipe through that from the merge, drill the piss out of it, and put a bad ass exit tip on it.
Not going to do a hell of a lot (I think) to quiet it down, but hopefully it adds a little bit of back pressure so I dont risk burning up the exhaust valves people say ducati’s like to do with straight pipes.
heres a nice write up. i was reading about exhaust designth in a couple books and they say its hard to get it exact just as mentioned in link. but if you take some time youll get it right
2 strokes need back pressure so thats a good easy to find design to look at.
looks like you know what you doing but a different perspective might help
Bike is running good and rides great. It needed exhaust in a bad way, so I set to work.
Made everything but the first few inches of the primaries into the head, no need to replicate them when I can just reuse the ducati originals. I made the muffler baffle like a short version of the Screamin Eagle baffles for HD’s. Made the end caps to slip inside the 3" SS slash cut tip, welded on the baffle tube, wrapped it with packing and secured it with some SS tig wire. Cut the muffler caniset to shape and slide the baffle in. Sealed with gold high temp silicone and secured the baffle with 4 rivets.
As you can see its a 2-1 design, I made the merge from 2 mandrel bends splayed together to converge nice and smooth, then slip fit into the baffle nice and tight, then held together with 2 dirt bike exhaust springs and tabs, as well as secured and located with the bracket to the engine case behide the rear barke. Which still needs to be formed against the muffler better and final welded.
Primaries are 1.5" 16GA. The forward cylinder was re-routed VS the factory pipe to allow access to the oil filter and drain plug a bit better and knock 2 inches off the total length leading to the collector. The rear cylinder is naturally going to be a bit short to the collector unless I sent the tube forward under the motor and 180’d it back in, which would be hard without a 2" or less CLR. So I decided to shorten the front pipe a bit as mentioned and try to lengthen the rear pipe as much as I could to get them a bit more equal length. the factor ducati pipes were different lengths by 4", the combo of pipes I made is now only 1.75" different front vs back primaries.
Dont mind the welds, the tubing is mild steel and its getting header wrapped anyway… so it got a bit more heat and more filler so it wouldnt crack being shaken to death on a V-twin. This was my first exhaust on a bike made from scratch so I was not about to sink the money and time in tigging up SS so clean I can eat off it, when I didnt even know if the exhaust was going to work!
So here it is, needs to be wrapped and muffler powercoated. But it looks cool, and sounds great. Much quieter than straight pipes, decel pop is almost totally elliminated, deeper tone, added a bunch of back pressure and richened up the tune. Powercommander is installed and flashed with the “K&N no air box lid and slip ons” file then I can tweak it from there. Runs night and day different on the short blast down the road and back last night.
it was 1AM and I just head to hear my hard work pay off. went down the hill, turned around and came back to park it and go home. I could have gotten hit by a mac truck the moment I pulled away too, so I know it doesnt matter the distance.
Idk I just dislike the sound, it looks fucking awesome though!
I mean, it sounds like I’d expect it to sound, but I love the bassy thump thump thump sound these make stock. It just sounds like a harley with a shitty exhaust now lol.
I don’t think I’ve ever said I liked a stock exhaust over a pie cut, dope, slash cut dump on anything. Weird. I must be getting old.
the camera phone doesnt do it justice at all. And thankfully sounds nothing like a fart can harley IRL. It sounds completely different. Also the stock exhaust was a silent hum. lol sounded like a hover. haha
Ill have to shoot another video with a decent camera.
2.5" CLR to keep it tucked up tight. and the verticle cylinder needed such a tight bend no way a mandrel would get me that. And i think its easier to tape and spin a bunch of wedges around to get from point A to B and do all the math and crap to find the right deg to find a hunk out of a mandrel.
I actually started with a bunch of U bends, put about an hr into trying to get them to fit right and got all pissed off becasue they were way too wide.
He sent me that via a text message he haven’t posted a build thread yet I think it would look sick on any twin the swing arm is off of a Honda vfr easy to modify and make work
