- This is a carburetor and
this is a special 3D printed see-through carburetor. And this is a high-speed
camera with a macro lens on it. You see where this is going. If you've ever cranked some
type of lawn care product, with a small engine on it, you have interacted at some
point with a carburetor. The question is, what does
this little device do? Yes, it mixes air and fuel together. But how, like, I want to understand how it works. As a mechanical engineer, I thought I had an understanding
of carburetors until the day I went to visit my dad who was replacing a
carburetor on his tiller. My dad is a really good teacher
and he has a really good understanding of how
mechanical things work. So I decided to suspend
everything I thought I knew about carburetors and just ask him
to teach me from the ground up. Teach me. What followed was a 45
minute lesson on everything about carburetors. - That's the main jet carburetor. See the holes on the side. Bowl, you got gasoline in there. - Uh-huh. - Float. See the needle going up
and down right there. - Yes, sir. - That's the throttle right
there. You can see there. Choke. We running open right there. Suction. The intake when the cylinder goes down. - It's a vacuum. - It sucks air through here. Put your finger up there, and the vacuum will pull this right open. The valve closes in the cylinder, the compression stroke comes up and compressors the gasoline. The spark plug fires,
pushing it back down. (engine turning) That's smooth. Works well. - So my dad gave me a masterclass
in how carburetors work. What I'm going to do is try
to explain in brief detail what he taught me. And then we'll move on to
the see-through carburetor, where I think you can understand
it a little bit better. So most carburetors are either
aluminum or thermoplastic. So let's look at this aluminum here. Most carburetors have some
things that all look familiar. Like you've got some kind
of little turny thing here. On this side, you've got
another little floppy do. And down here, if you take off the bottom, you can see that there's
some type of container on the bottom and a little thing
on the inside, right? All this looks kind of normal. Like if you've ever looked at an engine, you've seen stuff that looks like this. The thermoplastic version
kind of the same way. Okay. So what I want to draw your
attention to is there's two main components to a carburetor.
There's the top part. And the bottom part, and the
top part is called the Venturi. And the bottom part is called the Bowl. So in order to understand this, I tried to figure out if
I could find a see-through carburetor and I found
two different versions. Number one, I actually found a see-through carburetor on the internet. The problem is the guy that
sold it to me made me promise I wouldn't run gasoline through this. It was for teaching only,
and I'm a man of my word. So we're not going to run
gasoline through this carburetor. So I was left to try to find other sources for see through carburetors, and I found one on the internet. There's a young man in Pennsylvania. He created this. It's basically a see-through Venturi, which is part of a carburetor, but it didn't quite do what I wanted, which was to show the complete inner workings of the carburetor. So at this point, it's clear, we're going to have to make
our own see-through carburetor. And remember there's two components of the carburetor, right? Okay. First, let's talk about the Venturi. If you are like me and you have really old books on your shelf, you might have one that explains
carburetors in great detail and explains that a Venturi
is a really cool thing where you take fluid, that's
flowing through a pipe. If you neck it down at
some point to a smaller cross-sectional area, the static pressure at that point at the throat decreases. Creating kind of like a
vacuum in that one spot. Well, that can be used to
suck fuel up into the Venturi. All right. So let's look at that. So the Venturi part of
the carburetor is for sucking the fuel up into the line. The second part of the carburetor, the Bowl is for holding the fuel. So after a lot of collaboration, conversations and actual
engineering meetings. We came up with a 3D printed solution for a see-through carburetor. It consists of a laser 3D printed housing, which incorporates both
the Venturi and the Bowl. And we removed a float and
needle from a thermoplastic carburetor made by Briggs and Stratton. We laser cut our front cover that would allow you to
see the entire thing. And then we 3D printed a
choke and throttle lever out of PLA plastic. So this is the 3D printed
see-through carburetor. On an earlier episode of Smarter Everyday, I described a see-through
engine and we actually get see the combustion
happen inside the cylinder. Basically there's four strokes
to a four stroke engine. You have the intake stroke, which is where it's
pulling in fuel air mixture into the cylinder. After that you have
the compression stroke, which compresses the fuel air mixture. And then you have the
ignition at the spark plug, which creates the power stroke,
driving down the piston, and then the valve at the top opens and you push out in the exhaust
out of that valve and you start the whole thing over again. You have intake,
compression, power, exhaust. Intake, compression, power exhaust. The interesting thing
about the intake stroke is that it is a vacuum. It is
sucking air into the engine. And what we can do is we
can take advantage of that. Hang with me. This is a
little bit complicated. So this is the carburetor and let's assume the engine
is out here to the right it's taking advantage of the fact
that the intake stroke has a vacuum and it makes air want to flow this way into the engine. So once air starts flowing this way, what happens is air comes in
this side and it starts necking down into the Venturi there. Like we said, in our book earlier, where flow is high, pressure's low. And so if you have gasoline
down here in the Bowl, down here, all full up right here, what you do is you have a
little bitty of pipe right here, like a straw that goes up and goes into the center of the Venturi. And what that does is that
creates a little bitty jet of liquid that comes up right
here because of that vacuum. And then once that happens, it mixes and then it goes downstream into the engine like this. So basically you have
nothing but air on this side, you've got the fuel coming up here. And then you have the mixture
that goes from here forward. That's basically what a carburetor does. The choke in the throttle up top. That's the flappy things
we were showing earlier. That's the choke and that's the throttle. Basically what they do is control the mixture
that goes to the engine. If you close off the choke
and you restrict the amount of air that goes down into the Venturi, then you can create what's
called a rich mixture. Meaning the mixture that goes to the engine is rich in gasoline. You might want to do that if
you're starting the engine and it's having a hard time firing up. If you want to lean the mixture like this, that means the mixture
downstream is lean of gasoline. And there are different
reasons to do different things. But if you have an ideal
mixed choke right here, and you have full throttle, then you're going to have
great chemistry downstream. It's going to make the engine
run really, really fast. So these are the two controls
that most carburetors have. And this is basically the simplest design for a carburetor that can exist. So let's go get dad to show us
how to use this thing and see if we can catch it in slow motion. The first thing we had to do
is actually hook the gas line up to the carburetor. - Okay, I'm going to open the fuel. Here goes. - And it'll just fill up. - It should. - Ah, it's doing it. (laughs) I don't know why. - Didn't you know that's
what the Bowl was for? - No, I did not know that
was what was going to happen. - Well, yeah. - I mean it's obvious, now that you do it. Fuel flows in here and when
the float starts to float, it moves this needle, which presses into the seat and stops the flow of fuel into the Bowl. So you always have the right amount. Now backfiring is an issue.Right? - It is an issue. And how about getting this. - Ready to go? - Yeah. Cause we spilled some
gasoline a few minutes ago. - So if, if a backfire happens,
if I understand correctly, fire's going to come backwards
back into the carburetor and we did not pressure
test this carburetor. - Right. - So this this could explode and all this gas could be on
fire and go around us. Right? - Hopefully not. (laughing) As a matter of fact, open
the door just a little bit to let whatever vapors
here on the floor, go out. - Okay. - Ready? - Yeah. (engine cranking) Oh, I saw some vapor. - Did you? - On the intake stroke. Yeah. We're going to see it. Aah, it's running. (inaudible) We can kill it. - (Father)Kill it? - (Dustin)Kill it, yeah. You can see the vapor in the intake. - Can you? - Yeah you can. Did you see it? - No. - What do you mean you didn't see that. - I'm looking for fire. (laughing) Okay. Did you catch it? - I don't know. I think,
I hit the buttons. - It was running rich. It's
sputtering, sput, sput, sput. So I open the choke up so
it lean out the mixture and it started running smooth. - Like it. Like, it was
actually supposed to be. - Well yeah, that's what it's for. I didn't know there'd be
bubbles and things here. - Oh, look at that. - Look at that. - You see it? - Yep. (rapid firing) (instrumental music) You can see air, air-fuel mixture going in the combustion chamber. - This is intake. - Now intake is... - (Dustin)Is when it's sucking in. - (Father) Right. - (Dustin) Intake. - (Father) Yeah. - (Dustin) Fire. - (Father) Intake valve closes. - Closes exhaust stroke. - (Father) Yes. (together)Another intake. - (Father) Right. - (Dustin) So can you run two cylinders off of one carburetor? - Oh yeah, yeah. Or three or four. Yeah. - (Dustin) Really? - Yeah. - (Dustin) Okay. - The carburetor, all it does
is mix fuel and air and yeah, you got one carburetor
that runs eight cylinders. - (Dustin) Are you serious? - Yeah. - (Dustin) So it's running
really, really fast? - Each cylinder sucks in
what it can use burns it. Sucks in only what it can use. - (Dustin) Volumetrically. - Right. Now my motorcycle has a
carburetor for each cylinder and you have to balance those. - (Dustin) Because if you have one, one that's hitting harder
because it's getting a different. - Right. It won't run smooth at all. - (Dustin)So the advantage of running multiple cylinders
off of one carburetor, is you get the same
Stoichiometric mixture throughout. - Yes. - (Dustin) You can see the
vortex behind the throttle. Do you see that? - (Father)You can. Oh, it is. It is. Turbulent flow is a vor,
vortices turbulence. - Yeah, absolutely. You're just trying to get me riled up, cause you know, Derek
might watch this video. - Yeah. I like Derek. - I like Derek too. What would you change on
this design? Like now? What would you change? - (Father) I would make
the control stiffer so that when you put them in position, they would hold themselves. - (Dustin)Okay. - (Father)The engine sucks
the throttle open. Yes. - Oh does it? - It does. run away. If you don't physically restrain it, it gets faster and faster and faster. - Really? There's no governor. Yes. It's trying to pull that open
and I'm holding it there so that it does not because
I don't want it to - (Dustin) Run away. - (Father) Right. - (Father) You feel how
tough it is to move this? - (Dustin)Yes. - It's difficult to move on purpose. - I understand carburetors now. - Better? - Way better. Yeah. I mean, I guess nobody
actually a hundred percent understands it. - Well I couldn't do what I wanted to do. I could not make it run because
it wouldn't hold its setting position, but man, it works. - So when you just went wide
open, would it run wide open? - Well, I didn't want it to run away. - Try it. We got a fire extinguisher. - Well you got centrifugal forces. You tear the engine up.
You can run away too fast. You've got governors. You got throttles. You got control in a
factory built carburetor that we don't have here. You could get, you could. - I could get hurt. - We could tear the engine all to pieces. - Okay. - By supplying more, it'll run faster than it's designed to run. Can you zoom into that? - Yes sir. I can. I can get a tighter lens so
we can zoom in and we can see the fuel come up into the Venturi and then we can it vaporize. - And get blown away. Get blown away. - You wanna do that? - Yeah. - (Dustin) Let's run it steady state as fast as you're comfortable. - I'll try to, but I can't. I'm going to have to put
a finger right there. I think it'll just start right now without a choke. - With a finger or fenger? - A fenger. (laughs) (engine running) - Okay? - Got it. (engine sputtering) - (Dustin)Almost kill it. - That's a good carburetor. (instrumental music) - (Dustin) So the fuel is
coming up into the jet. That's the main jet, right? - (Father) Where's that
entering, right there? - Yes. It's coming
straight up in the middle of Venturi and then the intake blows - (Father) Air. - (Dustin)blows air across it. Look at all the stuff dancing down there. Let's run it again, and just look at the top
of the fuel in the Bowl. I just want to see what that looks like. (engine starting up) The mechanical oscillations
are way more violent than I expected. - (Father)The engine is running
pretty fast right there. Each time you see a shake
is a stroke, isn't it? - No, I don't think so. - You don't? - I think it's a vibration
mode. I think it's a harmonic. - (Father) You think it's a tuning fork? - (Dustin)I do. - There should be four. Should be intake compression. - Power stroke. - Power stroke, exhausts. - Yes. - So should have four strokes for each. And you do have, if you're
look at it right there. 1, 2, 3 suck. 1, 2, 3 suck. 1, 2, 3 suck. Top dead center and bottom dead center. - You're pretty smart for a redneck. Well, that's why they call it four stroke. (both laughing) - Okay. So now we
understand the carburetor on a macro level. We have built a functioning
carburetor, which is awesome. But now what we need to do is
I want to see the tight stuff. Like what happens when that jet
of fuel comes up and the air intake comes over the top of it? What does that look like? (engine running) - (Dustin) Got it. - Ooh. - (laughing) Yeah, I know. (instrumental music) - (Father) It's suspended. A drop of fuel was suspended in the air and then suction comes
and breaks it all up. Derek is gonna to love that. (both laughing) - Because of turbulence. - Yes. There's change in the laminar
coming in here, too turbulent. Ooh. - Converging diverging, nozzle. It. So a carburetor is
just a rocket nozzle. It's a rocket nozzle. Is what it is. I mean you're speeding up. - (Father) Watch it. Oh, oh, oh, oh. - (Dustin) It's a little drop and - (Father) Yeah. Carburetor tries to do is
increase the surface area on a molecular level. Right? - What do you mean? - In order to get full
and complete combustion, you need all the surface area
that you can get of the fuel. - (Dustin) Because ideally
you have an oxygen molecule right next to a fuel molecule. So now I'm going to get
what happens right when you pull the rope for the first time, when there's no fuel in the
carb to when fuel goes in. I'm gonna see what that looks like. (engine running) - Got it. (engine sputtering) - Getting some air from somewhere. - It's fun that we almost
couldn't turn it off. There's a little bit of risk. - (Father) Perpetual motion machine. (both laughing) - Oh, look at this. - (Father) What? - (Dustin)So on the intake
stroke here, you see the rope. How cool is that? You can see the rope in the foreground and you see the carburetor. I could not have imagined
a shot like this. - Oh wow. - Yeah. - Pam, Pam, Pam. (Dustin) Time to a time to mill those out of aluminum, I think. That's PLA, so I bet that PLA
is getting broken down by the, - (Father) By the gasoline. Because it wasn't that
flimsy to begin with. - (Dustin) You can see
the fuel coming up in the, in the straw and the jet. Look at that. You can see, - (Father) You can. - (Dustin) See that the flow right there. You can see everything. For the next shot. We wanted to see if we could shoot the high speed down the throat of the Venturi. So Trenton jumped in to help because we needed more hands. Just pop the choke out. And then we're just gonna
look straight down the barrel. - (Father)I'll pop the
choke about three-fours, or at least half of it. Yeah. - (Dustin)All right. So that's going to lean our mixture, right? - (Father) Yep. - Are you pulling focus? - I'm going to have to once it's running. - Yeah. (engine running) - (Father) You're going to
have meter with your finger. - (Dustin) Yeah. So I'll meter it with my finger
and you grab the throttle. Throttle is wide open right now, but it shuts off automatically. So if you'll grab it and shove
it back the other way that will keep it there. - (Father) That way? - (Dustin) Keep it there, yeah. (engine running) (inaudible) - I can literally
throttle it with my thumb. (laughs) - (Trenton) Come on. - (Dustin) Yeah. Okay, hold on. - (Trenton) I can't focus
because of your thumb. - (Dustin) Ready? - (Trenton) Yup. (engine running louder) - (Trenton) Okay. - (Dustin) Did you get it? - (Trenton) I think so. (engine sputtering) - (Dustin) Die engine! I don't want you to have
any, oh, I'm getting it. Oh my goodness. - (Father) There's your
vapor. There's your vapor. - (Dustin) I saw the vapor. - (Father) There's your vapor right there. - (Trenton) Got it. - (Dustin) Where? Coming out? - (Father) No, in the intake manifold. - (Dustin) Oh yeah. Whoa that's, that's vapor. - (Father) Yep. - Okay. So - (Father) Vapor go away. - What just happened, is dad cranked it I covered, I choked it with my hand. He was operating throttle. For a second there we
were. We were vibing. - Yeah, we were insane. (laughing) - So I was running choke.
Dad was running throttle. Trent was trying to frame the shot. Oh, I just hit your mic. It flattens the dropout. - It does, it does. - It flattens the dropout
and it distributes it. (instrumental music) Look at it. (instrumental music continues) - (Dustin)I now have a
three-dimensional understanding of how a carburetor intake air interacts with fuel
coming up in the main jet. - That was worth it. - (Dustin)This journey started by simply asking my dad how carburetors work. And by taking the time to
build and operate one by hand, we learned that the design
of a carburetor is simple yet very complex. And the fluid dynamics at
play are downright beautiful. (instrumental music) So I know a lot of times when
you get to the ad portion of a video, people kind
of like click away. They're like, oh, I'm
not interested in that. But I want to tell you why
I chose to work with this particular sponsor for
this particular video. When I look at a complicated
concept, like a carburetor, that's a very difficult
thing to understand. So one thing I like to do is I
like to build hands-on models and understand what's going
on by playing with all the variables and getting to
the point where I have a fundamental understanding of the concepts. Well, the sponsor for
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about carburetors with me. This is a fantastic
device. It's interesting. The carburetors suck as my dad says, but you get the Venturi, you got the ball. I just really like
understanding how things work. And I hope you enjoyed that as well. Feel free to subscribe. If you feel like this video has earned it, if not, that's no big deal. I do think you would enjoy
seeing the second channel where I get to talk to my dad in greater
detail and you get to see the light bulb come on in my mind as he explains everything to
me, dad's a great teacher. So feel free to go check that
out on the second channel. Feel free to subscribe.
If you're into that. If not, no big deal. I'm
just glad you're here. I want to say thanks to all
the patrons for supporting SmarterEverDay. Let me do topics that I enjoy myself and I'm grateful for you. Anyway. That's it. I'm Dustin. We're getting
smarter every day. Have a good one. Bye. What do you think dad? - It's a lot of work. That's what I think. It's not as fun as what I thought it would be from a distance when I'm
sitting at the keyboard and reading the comments. It's fun. But taking the video shots, I don't need more think about editing. Not many people that I know can say that they have made a
carburetor from scratch. - I wouldn't necessarily
call this scratch. - (Father) But now people who
actually work on small engines could give you a lot more educated words than what you're getting. - I don't want a person that is paid to work on small engines. I want to learn about
carburetors from my dad. (laughs) - You could have picked
anybody going down the street. - I think you're doing all right. - (Father) You got more information? - (Dustin)I think you're doing just fine.
He also made a video about an engine with a see through top, quite a while back. Very cool to watch.
https://youtu.be/xflY5uS-nnw
Even if you're not into motorcycles, you should be watching Destin.
I KNEW IT! Turney things and floppy-doos! Man, I'm so relieved it's not just me.
Saw this the other day and it's definitely one of the best videos I've seen in awhile. Everyone who owns something with a small engine should watch it.
Saw that yesterday. I worked in a shop back in the day, we rebuilt carbs. They really were the brains of the operation and the most troublesome things.
The REAL mystery about them is keeping a usable mix during the different cycles like idle, cruise, power, choke, etc... That versin is a very simple one and yet you can see just how involved it is.
Does anyone have the stl i'd like to print that
Nice footage indeed. Worth noting a lot of the 4 cilinder japanese bikes have CV carbs. They work on the same principle, but have a vacuum operated throttle slide. Also, many carbs have a starter circuit instead of a choke like shown in the video. Not to mention separate circuits for idle/mid/full throttle with, pilot/main jets, needles, emulsion tubes etc.
Carburetors man, that's what life is all about.
It's black magic. Carburetor is French for "don't fuck with this".