¶ Welcome and Episode Overview
Welcome to the Engine Noise Podcast, brought to you by our awesome sponsor, 1Auto.com, a podcast for do-it-yourselvers like me, who know exactly how to never finish a car. I am your car guy and favorite podcast host, Jeremy Nutt.
And I'm Matt Lantaine. And I hear you're there, Jeremy. Sometimes things just you just can't finish things.
Yeah, it just takes a long time.
Things come up, you know?
Sometimes you're like fifteen years old and you buy a project car and then pretty soon you're like thirty nine and the project cars So
What are you gonna do? Time time goes by pretty quick.
Yeah, I mean you know, it it's just hard to finish things. Years.
Yeah.
You know, you gotta you get a couple of things and you know, you gotta eat dinner sometimes.
Yeah, it's uh it's no it's totally understandable. You don't have to make excuses, Jeremy. It's fine.
All right. Today I have some cool talk.
Hit me.
So, the show lineup Alright, I'll tell you, Matt. I'm just gonna tell ya. I'm ready.
I've been waiting with bated breath.
All right. Today we have an important show about something that I hate and something that I love. Oh. That's right, we're talking about carburetors. We're talking about fuel injection.
Uh huh.
You can guess which one I hate and which one I love.
I I am gonna say carburetors.
Yeah.
Yeah, I don't blame you.
Now, the listeners might be saying, Jeremy, you have already told us about carburetors and how they should be left in the eighteen hundreds and that they should all be locked in an abandoned salt mine. Uh-huh.
Yeah.
And yeah, you're right. I don't like carbon. We have not discussed the evolution of carburetor. And the one carburetor that will never flood your engine. Oh
Interesting.
Still fun fact. And we have also never discussed all of the totally rad types of fuel injections. I think at some point we might have talked about like some direct injection or something. And maybe we talked about a little injector stuff here and there. But we never really covered the batch fire injection, the throttle body. injection the multiport sequential fuel injection. So we're about to cover all these in one absolutely beautiful episode of I love it, Jeremy. Yeah, so
Let's go.
Engine Noise Podcast is brought to you by oneayauto.com, quality auto parts that ship quickly and come with thousands of free online videos that walk you through your installs.
Thank you.
🎵 Music
You remember that year, right?
seventeen thirty eight. We're going way back.
Yeah, how old were you then?
Uh, I think I was like two.
¶ Bernoulli's Principle: Carburetor Foundation
Oh.
I was still I was still really bad at math.
Yeah, yep. Well, in seventeen thirty eight. Um, I'm pretty sure like around then it was one of those things where if you l really liked rocks in seventeen thirty eight, you could just start calling yourself a geologist because you just really liked rocks.
Why can't it be like that now?
I don't know. And then like if you really like science, like then you just start calling yourself a scientist. Like I don't know if you actually need qualifications to to just become things in the seventeen hundreds. I don't know. But I'm pretty sure.
Is this where like the last names were established where you just did that thing so that was your last name? Like
Yeah, I think it probably
Yeah.
If you made sure. Yeah, I think that was pretty much it. So in 1738, it's it's a weird time, you know. The the world is going through some things, and There's this guy named Daniel Bernoulli, and he was a Swiss mathematician. Now, you may remember that I just mentioned that I think pretty much anybody can call himself a mathematician in the seventeen hundreds, and that may or may not be the case. I don't know.
Are you trying to downplay Bernoulli?
not I'm not downplaying him'cause he did some great stuff. Okay. But I'm just saying, you know, I don't know like in the set in seventeen thirty eight could I call myself a mathematician because I really like doing multiplication. I don't know. So Daniel Bernoulli allegedly was a Swiss a Swiss mathematician. Now, he was probably pretty legit because he wrote a book in 1738. called Hydrodynamica, which is a dope name for a book. Wow.
I know. It pretty much could be. And if we start a band, Matthew.
Not a bad name choice right there.
Hydrodynamica is a So in this book that he wrote, he talked all about fluid dynamics.
Which is the same thing.
I think you'd have to be probably pretty smart to to write about. So I'm I'm giving Bernoulli his credit. So with the fluid dynamics came Bernoulli's principle. Ooh, which... Lucky. I mean, yeah, pretty pretty cool. So he came up with this principle. That said, an increase in speed of fluid occurs simultaneously with a decrease in pressure or decrease. And you know what? I read that and I was like, I don't know what that means.
Yeah.
So then I started digging into it a little bit and it turns out I'm gonna I'm gonna explain this in Jeremy terminology. Yeah. So imagine you have a cup of water. Mm-hmm. And you take this cup of water and you drop a straw in it. And then you send a whole bunch of air over the top of the straw. So you're like blowing over it. Yeah. Yeah. When you do that. The straw will draw the water up from the glass through the straw, and it will spray out the end of the of the straw.
Is that true?
It's real, yeah. This is like a thing.
I how come I've never done this before?
It's a science project that you should totally do. And the way if you really want to do this in your house, the way you do it is you get the cup of water, you put a a straw in it, and then you get another And you use that straw, the the second straw, to put it in your mouth, and you blow air like right at the top of the straw that's in the glass. Yeah. And when you do that All kinds of water will basically come out of the cup through the straw and spray all over your top.
Well I I wanna do this right.
I know, right? Sheesh. So this is basically Bernoulli's principle. This is basically him saying when you put a bunch of air over um over something, it's going to cause a low pressure area which will then draw fluid up the straw and spray it out the top of the straw. Boom, Bernoulli's principle in Jeremy terms. Yeah, it's really cool. And that is how carbureting.
¶ Carburetor Mechanics and History
So a carburetor is basically this cup of water Filled with fuel instead of water. Yeah. And the straw is the venturi that is in the carburetor. It's just basically a tube. Oh. Well, it's just basically a tube. And it's like it's narrowing the gas. Yeah. In the carburetor there's like a there's what's called a carburetor float bowl.
I know that.
Which is basically just a cup.
Yeah.
Yeah exactly, yeah. So it's got the float bowl. Uh-huh. Now in that bowl is a bunch of gas. And coming out of that bowl is a tube, which is called a venturi, and that tube has a very small orifice. Very small like it's a very small tube. Yeah. And as air passes over the end of that tube, it draws the fuel out of the tube and into the engine, like through the carbon.
Okay.
Pretty kinda it's kinda cool. So that is how that is how a carburetor works. It works because of Bernoulli's principle. And you're probably saying, well that's all cool, but who actually invented the carburetor? And I'm about to tell you.
That's exactly.
Right. There's this guy named Samuel Samuel Mori, and in eighteen twenty-six he invented the carburetor, according to the But his method of carburation was a little bit different than what we just talked about. His was basically you have this cup of fuel and you just pass a bunch of air over the top. And the air going over the fuel just kind of takes the fuel fumes and it drops it into the engine and the engine runs.
And that's all well and good, but it's not as good as it could be. The using the straw into the fuel uh float bowl is a much better design. And that is where our friends Carl Benz, who you may know from Wilhelm Maybach from the Maybach Car Company and Gottlieb Daumler from Daumler Chrysler. Yeah, I know. But all these dudes were pretty much right at the at the forefront of carburet in the late eighteen hundreds. They were all like coming up with new carburetors.
and they're basically the ones who took Sam Maury's design and kinda turned it into what the modern carburetor is now, where you have Venturi going into a float bowl and you're actually atomizing the fuel and it's going to be a little bit more than a little bit. So pretty cool.
Question for ya.
Cảm ơn các bạn đã theo dõi.
What produced the air or like pushed the the fuel into the From the Venturian.
Yes, it's a negative pressure inside the engine. So when the piston goes down, it causes a negative pressure inside the engine because the valve is Closed at that point and the piston's going down, and then the valve and then the valve starts to open up as the piston's going. And it draws in a whole bunch of air and fuel mixture f through the carbon.
I see now. That makes sense. That that is her newly printed.
Exactly. And then because there's so much air rushing in, it pulls in the fuel with it going past that little venturi and you get the right mixture. You do a little tuning on the carburetor to make sure you get the right air and fuel mixture.
You never do. You never do.
Yeah, yeah. And then on the other side of the carburetor there's a throttle plate and that throttle plate gives you more or less air going through the carburetor. Um and then there's also another plate in there called a choke. And what the choke does is the choke basically blocks off all So that means the piston comes down, it draws in like way more fuel than air, and that's what a choke does on the engine. It basically floods it with fuel so that it can start up really easy.
And then as soon as the engine's running, then you turn off the choke and it gets the normal air fuel ratio and it's a much happier running engine. Okay. Yeah.
So most early cars had cars.
Right. Yeah. Cars pretty much had carburetors from uh the late eighteen hundreds right up until like the nineteen early nine. Yeah, but these carburetors came in three different styles general.
¶ Updraft, Downdraft, Sidedraft Carburetors
And in the early, early days of automotive uh design, there were updraft carbs. And an updraft carburetor means the air came up from the bottom and through and out the top of it. Okay. And you would find these usually on cars between the late eighteen hundreds and probably the early nineteen twenties. And you'd also find these on tractors. So if you ever go see an old tractor that's like, you know, we'll say 1930 and before, it probably has an updraft carbon.
So I ran I know around Massachusetts every ice cream stand seems to have an old tractor in front of it. So the next time you're at an ice cream stand and you see an old tractor sitting nearby, go check it out because it's probably got an updraft carbon.
Yeah, yeah.
Yeah. And the cool thing about updraft carburetors You pretty much can't flood an engine with an updraft carburetor, because when you flood an engine, it basically means that all of this fuel is kind of sitting in the intake manifold, and it's just too much fuel. It essentially like wets all the spark plugs and the spark plugs don't want to fire and it just floods the whole thing out with fuel and not.
But if you have an updraft carburetor, the fuel can't pool in the intake manifold because the fuel would just drip out the bottom of the carburetor. Yeah. That is a fun fact about updraft carburetors. But the problem with updraft carburetors is oh actually let me tell you one more fun fact about updrafts. Updrafts are also cool because you can have them really low on the engine.
And you can gravity feed fuel to the carburetor. So you don't even necessarily need a fuel pump because you can have the carburetor so low that it can be lower than the fuel pump. And you can skip the fuel pump altogether and just run straight fuel from the tank to the carburetor and up to Interesting. Yeah. The downside though of updrafts was that they were so low on the engine and it made them it made the intake manifold and the carburetor take up a lot of valuable space.
So what ended up happening was a lot of engines kind of swapped over to be downdrafted. And a downdraft carburetor is probably what most people think of carburetors today, like a modern carburetor. It has air that goes down from the top, goes through the carburetor, and the air fuel mixture goes out the bottom. So if you pop the hood of your
Let's say nineteen seventy Chevelle. Yeah. You got your big block four fifty four in there, you got your four speed Muncy out back. You got your four eleven posse gears, you got your front disc brakes, you got your cowl induction hood. Sweet. And under that super cool air cleaner is a four-barrel carburetor. And that is a downdraft. comes in the top, through the air filter, through the carb, into the inner. Cool.
Now downdraft is great for like a V8 because the carburetor fits nice and snugly in between the two cylinder heads. It's nice and compact, and there's less parts Than if you were to have um multiple small carburetors or uh even a side draft carburetor. Now you're probably like, what the heck is a side draft carburetor? Am I right?
Well, I thought that was the original copyrighted, no?
No. Updraft was the original. Oh. So there's up drafts, there's down drafts, and there's side drafts.
Okay. I'm just I pictured o automatically the side draft because of the uh straw over the other straw technique. Uh
Ah right. Yes.
Gotcha. Okay, side quotes. Go ahead.
is what you would find on tons of different motorcycles. Motorcycles are like I mean, any carburetor on motorcycle is probably a side draft motorcycle
Side draft city. Side draft city.
It's what they You'll also find them on some really cool European cars. Some like maybe some older Jaguars, maybe some old Triumphs, maybe an MG or two. Um That sort of thing. Um there was a few American cards that came with side drafts as well, but they're just not as They're not very common. Some people will use them on performance scenarios, so maybe you have like a maybe you have a Honda Civic and you want to do And you want to do a simple carburetor.
Yeah. Now why you'd want to do this, I don't know. But you got a four cylinder engine, it's an inline engine, and you could put individual side draft carburetors on each cylinder. And it's really cool to do that because then you can tune each cylinder precisely with its own carbon. Oh so if you find cylinder three decid it wants to run a little bit richer than cylinder two, you can tune the carburetor perfectly for that specific.
Hmm. It's like uh close as close to digital
Yeah. Right. Yeah, it's pretty cool. So like in the updraft world you'd usually have one updraft carburetor for the whole engine. Yeah. And in the down draft world Most likely you're gonna have one carburetor. There is some exceptions where you'd want to have multiple like single-barrel carburetors or a couple dual-barrel, you have a tri-power. But with side drafts, you almost always have multiple side draft carbs.
And it's they sound really cool when you rev up the engine, and they are really cool for tuning. The downside of them is that they take up more space. Uh they require more expertise to tune them because now you have four carburetors to tune or six carburetors or eight carburetors. And it's, you know, you have to know what the heck you're doing to tune them all. And Yeah, there's just more pieces and parts.
So, unfortunately, the early 90s showed up and was like, hey dudes, carburetors are out, fuel injection is in.
Yeah.
Then people put on their roller skates and then that was the end of the car race.
Oh boy.
So she I know. And with that, I think we should do a little ad and then we'll talk about some fuel injections.
I think that's a great idea, Jeremy.
What is it?
🎵 Music
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🎵 Music
Alright, Matt. Are you ready to talk about fuel injection?
I sure am.
¶ Fuel Injection's Aircraft Origins
Yeah.
Alright. Way, way long ago in the nineteen
The Roarin twenties.
The Roaring Twenties. There was this this guy who was a Swedish engineer. And his name was Jonas Hessel. And according to the internet, he's the guy.
Bye.
Who pretty much came up with fuel injection?
Well, it's on the internet, Jeremy. Right. Gotta be true.
I know. So he gets the credit for inventing fuel injection, and legend has it that he did this for plane reasons. He basically wanted Guys in planes. Yep. Um, to be able to fly upside down and backwards and upside and like right side up and like down and up and all these different directions. And carburetors were like, We don't really like doing that. Oh.
Oh that's a good point.
Yeah.
I never thought of that
Yeah. So like you flip a carburetor upside down and now your float bowl's pouring out all your fuel.
Yeah. Well I didn't know that. I never flipped my tractor.
Ja, ik weet het.
Luckily I haven't done that.
Luckily.
Yeah. So Jonas Hesselman was like, you know what? We gotta make some fuel injection for these planes so we can do some cool moves up in the air.
Cool. I I find that to be a valid reason.
Yeah, totally. So he comes up with this uh this kind of crude fuel injection system, which is like mechanical fuel injection, and mechanical fuel injection is A very simple way of injecting fuel into an engine without having bowls of fuel.
Is there a just like some guy with a crank on the inside of the cockpit?
Just it's Yes. It's exactly that except without a guy, instead you have a belt. So you have like a belt that runs a pump.
Wasn't too far.
Pump. Yeah, exactly. And then the pump just has this like little rotating thing in it that pumps fuel at different times to different cylinders. And then you control how much throttle you give it by opening and closing the air that goes into the cylinder. So it's a very simple setup. It is really good for giving a an engine full throttle or a very little amount. Everything in between. Uh it's it's difficult because
When you rev up an engine, the whole revving like RPM range needs different amounts of fuel, and it's not always like a linear thing. It's not always like, okay, uh ten RPMs you give this much fuel and twenty RPMs you have double the amount of fuel.
So because engines you know have different fuel needs at different RPMs, mechanical fuel injection can be a little bit difficult to tune because it wants to be a very linear thing and that's So they're great for like drag racing because it's just like full throttle, straight, give it all the fuel you can do.
And it's probably great for planes because it's pretty much like give me all the fuel. But on like a daily driver where you're driving to work and back, you probably don't want mechanical fuel injection because it's not the best way to deliver fuel through the whole RPM range.
So what so what do what did they do?
So, naturally, fuel injection evolves. So they started um Basically electronics got involved and people came up with a bunch of different uh types of fuel injection. It was it was an evolution process from there. So that was in the nineteen twenties and it was a and it was uh intended for planes
¶ Electronic Fuel Injection: TBI and MPI
Then, you know, some people start putting it on motorcycles and cars and dirt bikes and like all kinds of weird engine scenarios. And It evolves until Well probably the nineteen eighties is about when fuel injection really kinda comes up to its i its prime.
I'm actually surprised it took that.
I know, right? Yeah. It took it took quite a while for it to catch on. And I think it was a I think it was a technological reason, um, because the technology just didn't exist yet.
Yeah.
to be able to control fuel injector injectors as fast as they needed to be controlled. That's my theory at least. I don't know.
I guess that combined with like the carburetor worked for so long so
Yeah. Yeah, exactly. The nineteen eighties come along, and things are pretty cool.
Oh yeah.
And you know, the music's pretty great. So cool. Obviously. And The car manufacturers are now realizing that they can take off the carburetor and put a throttle body fuel injection setup pretty much in the exact same spot that the carburetor. So they need to do very minimal changes to the rest of the engine.
And they can just plop this throttle body fuel injection in its place and everything's cool and now they have fuel injection instead of carburetion and they have a lot more control over the amount of fuel that the engine.
Which is totally rad.
Which is totally right. So they do that, and throttle body injection is really neat because like I said, it goes right in the place of a carburetor and it's got like either one or two injectors usually. Sometimes you have three, sometimes you don't. But generally it's like one or two injections. So it's very basic and there's just like a throttle plate that opens and closes and it has a throttle position sensor on the side so it knows where the throttle plate is.
So as the throttle plate moves open, it gives it a little bit more fuel based on the computer. And it's just a very basic design that just works. And That then evolved into multi-port fueling. So multiport fuel injection is like when you have an injector on every cylinder of the engine. So if you have an eight cylinder, you'll have eight injectors.
And this was actually really cool in its own way because If you're putting an injector like right at the top of the intake valve for every cylinder, now you have a lot more flexibility with your intake manifold. Um and it's it's sort of like the same um
The same thing I was talking about with the side draft carburetors where if you have the side draft carburetors, you can do like anything you want with the intake manifold because they're so simple. Um it's just a pipe that goes from the carburetor to the cylinder. And with the multiple or multi port fuel injection, you have the injectors right next to the intake valves in the intake valve. And then you have all this other space to do whatever you want with an intake manager.
In the case of like a car that has a interesting shaped hood or like a minivan. where you need to have the intake manifold like tucked under the cowl or something like that.
Oh, yeah, yeah.
And you need to put the intake manifold like down behind the engine. You can do that now because you don't have to have this throttle body injector setup that they previously had sitting right on the top of the engine. Now you can put the throttle body wherever you want it under the hood. And you can have an intake manifold that's any funny shape that you want, and it doesn't really matter because the the fuel is still going to get to the cylinders because it's right next to the intake.
And the throttle body the throttle body doesn't really care where it's as long as it's attached to the intake manifold. So it just gave the the engineers a lot more freedom to design different shaped intake manifolds for better engine efficiency and for better usage under the hood of some of these new uh newly designed cars.
Now if it was me and I had a minivan and the thing didn't fit, I would just use the throttle body, I'd just cut the hood and have a super sick intake on top of the hood.
Yeah. Exactly. I mean that I would do I would definitely do the same.
Yeah.
Um and along with the the individual injectors on every cylinder, this also meant that the engineers that were actually making the engines run, they had more control over each cylinder. So they could tune each cylinder perfectly just like you would with a side draft carburetor. It was um it was really specific um tuning for every single cylinder, which is really really cool to have. So then
¶ Batch Fire Versus Sequential Injection
There's two different types of injection that you can have in a multi-port fuel injection setup. You can have what's called batch fire injection. Which is basically you spray all the injectors at once and it doesn't really matter where the piston or what the piston is doing. Okay. So like so it just says, okay, every rotation of the engine, I spray the fuel once. Yeah. And all the fuel sprays at the same time and all the cylinders get their fuel and all is cool.
The other option is sequential fuel injection, which you see on a lot of cars, and that actually times the injector sprays. When the piston is in the right Right. So like as the piston goes down and it wants the fuel. Then the injector opens up when the intake valve spray or intake valve opens and it sprays the fuel in the cylinder, and then the intake valve closes and the piston starts to come back up. Yeah. And you have it all timed perfectly for every single cylinder.
And again, this makes the engine more efficient, makes more power, less emissions.
Yeah.
All the good things. Because like Yes, very much.
Just like kinda like burn a lot of fuel in one cylinder and then a little less in another at the same time and then like burn leftovers as it like went.
Um I think it probably burned the fuel um equally across all the cylinders, but what could happen is you'd end up pooling fuel behind the intake valve when the intake So the intake valve is closed and then the injector sprays and the injector or the fuel coming out of the injector just sits there waiting. Right. And for the intake valve to open. And then as soon as the intake valve opens, it kind of like pours into the cylinder rather than being misted in like in an atomized way.
So I w I would imagine that wouldn't be very good for
Yeah. Yeah, I mean it still works. Um it's probably still better than a carburetor, I would say. But it's not as good as the sequential fuel.
¶ Direct Injection: Peak Efficiency
And then lastly we have direct injection, which is the newest, coolest type of injection. It is. And this is what you'll find in a lot of new cars, new Corvettes. A lot of new a lot pretty much most new cars that are advertising really great gas mileage have some sort of new direction. And direct injection is cool because the injectors actually inject fuel directly into the cylinder itself. They don't go they don't sit behind the valve anymore. It is spraying fuel directly at the pit.
That is really cool because you can spray fuel at a much higher pressure, which means better fuel atomization, and better fuel atomization can lead to more efficient burning, which is more efficient use. Better gas mileage. And the other cool thing about direct injection is because they have such precise control over the fuel that is going into the cylinder. They can actually do multiple sprays of the injection. For one stroke of the pistol.
Oh so you'll have a piston coming up and it might spray just a little bit to get the fire going inside that cylinder. And then it'll spray a lot more when the piston is like just about to like reach the top of the cylinder and that could potentially make a whole lot more power and more efficient burn. Because there's already some fire in the cylinder, and now you spray more fuel on it and you get more fire and more pressure and you push the piston back down and all.
Sounds complicated.
It is really complicated and it all happens in like millionths of a second or something.
Yeah. Exactly.
So yeah, although like to a human eye it just looks like the direct injection is just spraying constantly, it's actually, you know, doing multiple sprays over the course of a few millimeter. Millionths of a second. I don't even know what it is. But it's very quick. And yeah, it allows for really precise tuning of the engine and yeah, you can get uh you can get a lot more efficient usage. So yeah, that is uh that is direct injection for ya, and uh that's all I got for injection Matt. That's it.
¶ Episode Conclusion and Farewells
I well super it sounds super complicated but Pretty cool and it makes sense as to why it took this long to I'm sure it's just gonna get better and better and better anyway.
Absolutely.
Yeah, exactly. We perfect it and then we just kill it, you know?
Right, it's like the Pontiac Fiero. You get it absolutely perfect in nineteen eighty eight. You have your lotus suspension, you got your your uh V six engine, your five speed transmission, you got your sunroof, and then you're like, nah, we're done with it. Something.
Things uh you know, just gotta come to an end.
Alright, well should we wrap this one up, Matt?
Let's do it. Alright.
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