How to Design a Tuned 2 Stroke Exhaust system Part 1

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Greetings to all and welcome to my YouTube channel, or welcome back.
As per the previous video on two-stroke modeling software we're going to branch
out into designing a two-stroke expansion chamber, now we don't need
all of the parameters that was covered in the previous video because it relates
to the modeling software itself. In this case we can actually work straight
towards designing a pipe for the engine that we've got now just be aware that
what I'm gonna show you here is how to design a pipe for the engine you've got
but you know you have to be satisfied that everything else is in order,
port balances you know the sizes the timings of each of the ports compression
ratios squish clearance and not limited to that, now if that's not correct okay
well we will do that a little bit later because after we've done the expansion
chamber one then we're going to move to things like this one specific port time
areas and and other factors that you might want to do first
if so then we'll get to that but if that's all in order and you're satisfied
that you just want to build an expansion chamber or you don't want to make any
modifications to the engine then watch this video and the series of this videos
I'll put it into one playlist so that we can keep track of it and we'll go
through the steps of actually what we need to design a pipe standalone pipe
and then go through these steps and the first one is taking some measurements of
the engine, exhaust port timing, the exhaust port area so that will cover how
to measure the exhaust port and any calculations related as well, calculating
our average cylinder pressure being brake mean effective pressure, the next
one is we do some calculations, most importantly we calculate our tuned
length of our pipe based upon our exhaust port timing, our header pipe
diameter, there's a bit of a trick there in relationship to the port area port
area diameter, the outlet diameter and the diameter ratios
further on in this calculation here. Horn coefficient, midsection diameter,
outlet diameter again and then we go on to basically do all the actual dimensions
the remainder of the dimensions of the pipe the length of each part and next
section and once we've done that then you actually get on to the actual
manufacturing or building of the pipe and we've got a few issues that we go
over there that you'd want to know before doing that but essentially these
three parts, this is all measuring and on paper so once you get to this part then
you actually committed to doing the pipe. You may not want to build an expansion
chamber right at this point but because it's a fair commitment once you actually
go to do the cutting welding and fabrication of the pipe itself it's not
something that you should leave until you actually are going to make one if
you've got the intention to making anyone in future it's a good idea to
basically practice this so that you're reasonably familiar with the steps and
you're reasonably familiar with what's going on there while you're doing it and
then calculating pipe because you can do that as many times as you like on paper
until you're you're satisfied with that before you actually get into the tools
and start making a pipe and commit to that. The first step, exhaust port timing
using a degree well which you can download one of these there's two links
up here the bottom one is actually a better one but you can stick with this
one either print it out in high resolution or DPI or whatever make sure
it's not too big good idea is to laminate it then cut out
sort of around the outside of the edge of the circle so you know you know
unseal it and that makes a little bit stiffer to put the center in and bolt it
on to one side of the crankshaft then you've got to find yourself a piece of
wire and attach it you can attach it to a fin or a bolt attached it to a fin
with a little vice grips if you like and then pointer down. Once we got our
degree wheel setup turn our engine over and look up the exhaust port
so we can just see the a gap between the top of the port and the piston in here
take a feeler gauge and just stick it in the top there okay and then push the
piston back until it's just touches or just pushes the feeler gauge against the
top of the top of the port just a thin feeler gauge just don't chomp it off and
then what we're going to do is we're just going to rotate the wheel around
until the zero until we get the zero on our pointer pointing to the zero of the
wheel okay so we just just get the zero point and make it zero being the zero
amount from when the you know feeler gauge sticks at the top and just make
that zero okay once you've done that turn the motor over alright, and then all
the way and then back again until the feeler gauge is pushing against it and
then mark the spot on your degree wheel with a marker pen where the
pointer is now okay, and what we're gonna do from that is we're gonna count how
many degrees of movement we've had for the exhaust port period being open
because that's what we need is this period in degrees all right so all we're
gonna do is we're just going to count that off the wheel as I said you know
you can do the true top dead center method if you like if you want to
get down into the degree but the fact is that because ports are symmetrical in
other words it opens the same amount of time after top dead center as it closes
before top dead center and we know they're gonna be the same each side we
don't really have to find a critical zero for this purpose, when you're
dialing in camshaft and a four-stroke yeah you do big time but that's a
separate issue alright back to the other screen. Okay to what I was referring to
before when you shove the feeler gauge in the port to stop the port you got to
point it to zero then you turn the motor over all the way until the feeler gauge
touches again and then you mark your wheel so now you've got a zero point and
you've got your mark as far as how far and just make a little mark on there
just use a marker pen or something and just mark that this is the period that's
open for okay so now it's just a matter of
counting down how many degrees you got on your wheel so you'll get a hundred
and eighty degrees okay so if the mark is here then we know our port timing is
170 degrees if the marks here it's 180 degrees and if the mark is here then it
goes down in numbers but she's just got to add 210 so 180 190 200 210 okay so
that's the period of opening and basically write down that figure as your
total exhaust period being open and then we will move on to the next part of it
which is using that to determine the tuned length of the pipe, but that will do
it for today for this video and that will be in the next one so I hope to see
you in the next video if you've got any questions don't hesitate to ask in the
comment section if you haven't subscribed please do it all helps please
share the videos and that helps a lot too and we'll see you in the next one
and bye for now
Unlocking the secrets of 2 stroke expansion chamber exhausts E1 Reed Valve V Rotary Disc Intake and why small 2 stroke engines favor the later. 2 stroke power valve, gas v acoustic velocity, exhaust port timing for expansion chamber. E2 The two tuned lengths of the 2 stroke expansion chamber, photo of compression wave formation. E3 Diameters for belly and stinger on 2 stroke expansion chambers, tapered header pipes E10 Active Demo of Wave Timing through 2 Stroke Exhaust Cone Sections. 2 stroke expansion chamber outlet bleed pipe and port plugging pressure explained E7 What is the effect on 2 stroke expansion chamber tuned length after raising cylinder ? E11 Simple Tuned length calculation 2 stroke chamber baffle cone, temp, gas effect on sonic velocity E4 The Secrets of Resonance Tuning in 2 Stroke Expansion Chamber Exhausts E12

How to Design a Tuned 2 Stroke Exhaust system Part 1

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