Homemade expansion chamber
This is a little thread about how i made my own expansion chamber at 16 years old, it was the first time i ever touched some sort of welding device and i had to make do with a mig welder for this exhaust, it worked great and was easy to learn, tho tig wouldve been the best option its expensive and i dont have one available to me.
But all in all, this project costed me 10 pounds, and that was how much i paid for my 1m^2 piece of sheet metal. Im not counting costs of the welder or weld gas etc, or all the other tools i used like a slip roller etc, i am lucky enough to have a great neighbour with a big workshop that let me use his equipment.
I used 0,9mm thick metal, for me it was perfect, thick enough to get okay welds on without blowing through and thin enough to not have a nightmare trying to bend it into the cones, in all honesty the slip roller is useless when it comes to making cones, id recommend that u do it on a round spikey object instead like an anvil but it also works great if u just clamped a piece of tubing in a vice and pounded the flat sheet metal with a rubber mallet around the pipe.
Since its my first ever pipe i didnt know what to plug into the software that spits out all the dimensions so i made it at 30hp at 10500 revs, also went in the middle when deciding a power band, i dont want it to be only between 10000-10500 but i also wanna be able to feel when u hit the powerband so i went roughly 50% in the middle in the software
I know the underslung design has many people torn, i think it looks pretty cool, unique and aggresive, but honestly for me it came down to the fact that an underslung is so much easier to make rather than a standard one, it saved me loads of time since im doing piecuts cause i didnt know the angles before hand, piecuts isnt optimal but i dont think it has a noticeable impact anyway, but yeah, for my first pipe underslung was the best option, and now when im finished im absolutely in love with the look if im gonna be honest
All i really mean to say with this thread is that nothing is impossible, if u have the tools laying around, maybe u have a dad with a welder or good friend with one etc, its not that hard to be honest give it a try, even if you dont know how a welder works beforehand just like me, its a great project to learn loads about the 2 stroke engine but also about metal fabrication
I will edit this with picture as soon as i wake up tomorrow since im not on my computer at the moment, sadly i didnt even take that many pictures tbh
Calum last edited by
Yes some photos would be grand.
Underslung will allow you to get greater performance. A wrap around is a compromise for ground clearance.
It's good you went out and messed around with some fabrication. Those types of skills are invaluable in the mechanical engineering space!
Im fixing the photos as soon as im able to get on my computer, the pipe doesnt look the absolute best but im still happy with the end result.
I also read a thread on facebook in the twostroke r&d group where they said that there practically isnt any difference in power in a well made up and over pipe compared to the underslung design, as long as u dont make any sharp bends and have a natural good flowing curves the extra bends of the up and over pipe doesnt impact gas flow to the extent where it makes it worse in performance, i could be completely wrong on this info tho tho
declan last edited by
@Arild I was looking into making a pipe figured i would run out of skill pretty quick so went off the idea I’d like to see how yours turned out though
This post is deleted!
Im starting my computer as im writing this to upload the pictures if i manage to do it
In all honesty it was pretty easy, and it doesnt demand thaaat much skill, or it does if u want an absolutely flawless pipe but for one that looks pretty good and makes difference minimal skill is required, the most importsnt skill to have for making ur own pipe is patience and even more patience, spending loads of time trying to get good cone shapes that fit with the next cones etc, or laying down good welds that penetrate but doesnt make a mess on the inside etc, it takes a long time but it isnt as challengine as people make it out to be, and i say this with never have touched a welder or done any kind of fabrications before, just a dream and goal in mind and lots of patience gets u there
Welding 0.9 sheet metal to sheet metal is no easy feat for anyone. Good going for your first time. You must have the knack of seeing the heat and balancing the wires speed. Love to see pics as well...
This is my first attempt at uploading pictures so i hope it goes well
I couldnt find how you get the pictures onto the thread but heres a link to imgur where theyre uploaded in the right order, first picture is the software i used to design it and all the dimensions i used, there might be something wrong in there and if it is pleaes tell me.
I cut all the plat cones out with an angle grinder and went around the edges with a flap disk to smooth all the jagged edges down, a hand held sheet metal cutter could also probably work fine, i found it a little tough to get through the 0.9mm thick mild steel with it though, and it also leaves a curled up edge were you make the cut, it could just be hit with a rubber mallet and it would be fixed but the grinder went faster
The welds are by no mean even close to perfect, but after you grind it all down it looks okay
Fair play bud! It doesn’t look too shabby, and you know it’ll only get better each try.
How many hours do you have into it?...
All in all i spent around 2 months making it, though i had school during the day and some days i didnt feel like going out in the garage, but maybe around 20-30 hours for me, might take longer for someone that has no idea what they are doing and someone really skilled with a welder might do it in under 20, but its not a short project and u gotta have loads of patience but when u see the end result and ride the bike and feel the increased power every second of it was worth it in my opinion, it was also honestly a really fun project, a fun thing to try over the summer break or while stuck in lockdown
This is the software i used
I dont know if its perfect, probably not as good as a paid software, but its still all the same principles when making a twostroke pipe, or it depends what formula u use, theres newer ones and more outdated ones but u can make a pipe with any of them that atleast makes a difference and is better than the original pipe
There is one software to stay away from though and it is the build and click exhaust wizard software, it costs around 20£ and is a complete waste of money, atleast to me, the diameters they gave me seemed ridicoulus, the widest section should be 7cm according to theyre program and it just didnt seem right to me so i just stuck with the free 2texcalc software and sucked up the fact that i paid 20 quid for a shit software
You can also find the FOS formula online which is a different way of designing and making them
Theres also a spreadsheet thats fairly good but for that one you need to know the area of you port which i didnt have by the time of that software and i still dont have it
I couldnt find a link to the download page of the program but its in the description of this youtube video, he goes through the excel sheet and what u need etc to make it all work.
declan last edited by
i really like that well done