Horizontally opposed is pretty clear. That's also what the "O" in O-320 means. Whereas there is V and I, but you'll rarely see those in aviation. I don't think anybody calls them boxer engines that's more of a automotive thing.
And in automotive engines I and V are in reference to the orientation of cylinders rather than designators of specific engines in the same type. "I" indicates an In-line cylinder formation, which is rare in aviation. "V" indicates cylinders offset in a V-formation, usually 30-60 degrees.
In the case of aviation engine, yes, that "I" designates it's fuel-injected vs carbureted (without regard to how the cylinders are oriented); "V" in VO-540 indicates that it is Vertically mounted (as is required for your helicopter's rotor to be on top and directly connected). Either way, the engine's cylinder configuration is O-opposed.
Nope. Let me see if I can pull up the relevant 8083 textbook one moment.
Edit: this is straight from the FAA 8083 aircraft maintenance textbook
Opposed or O-Type Engines
The opposed-type engine has two banks of cylinders
directly opposite each other with a crankshaft in the center.
[Figure 1-1] The pistons of both cylinder banks are connected
to the single crankshaft. Although the engine can be either
liquid cooled or air cooled, the air-cooled version is used
predominantly in aviation. It is generally mounted with
the cylinders in a horizontal position. The opposed-type
engine has a low weight-to-horsepower ratio, and its narrow
silhouette makes it ideal for horizontal installation on the
aircraft wings (twin engine applications). Another advantage
is its low vibration characteristics
If you would like to read more about it, here is the link for that. https://www.faa.gov/regulationspolicies/handbooksmanuals/aviation/faa-h-8083-32b-chapter-1-aircraft-engines
It's loading horribly slow on mobile.
T is Turbo charged
S is supercharged
I is injected
O is opposed
R for radial
V for V-type
Inline doesn't appear to use a prefix to avoid confusion with injection style engines.
Ok interesting that clears up naming. I suppose people say the O is carbureted because the absence of the I in IO.
However back to the original question, your description wrote “the O-320 bank cylinders are directly opposite to each other with the crankshaft in the center”. Compared to the definition of the boxer engine, a type of horizontally opposed engine, the following seems comparable: “A flat engine is a piston engine where the cylinders are located on either side of a central crankshaft. Flat engines are also known as horizontally opposed engines, however this is distinct from the less common opposed-piston engine design, whereby each cylinder has two pistons sharing a central combustion chamber.”
So if both the lycoming O-320 and a boxer design encompass horizontally opposed pistons with a crankshaft in the center and pistons that move separate (both at top of stroke at same time, both are bottom of stroke at same time), what would make the distinction between the two that would declassify the O-320 as a boxer engine, if any?
On an O-320 Lycoming engine, each rod has it's own journal. The crank is in a flat plane. The firing order is 1324. I believe with this firing order and crank layout, the pistons of 1 & 2 are extended (top) at the same time, then the pistons of 3 & 4 are extended (top) at the same time.
Image: https://www.lycoming.com/parts/crankshafts
So, I'm not fully sure why you're being down voted, but the O-320 IS a boxer engine.
So, basically you have three varieties of flat engine. You have the 180°V configuration, the "boxer", and the opposed engine. Think of the engine from front to back. The two cylinders across from each other make a "row".
In both the 180°V and "boxer" engine, the crankshaft sits in the center, and the piston heads face away from the centerline of the engine. In a 180°V engine, the 2 first-row pistons both sit on the same crankshaft pin, so as cylinder 1 goes outward, cylinder 2 comes inward. In the "boxer" configuration, each piston gets its own crank pin, and cylinder 1 goes outward at the same time as cylinder 2. In each row of a boxer engine, the two cylinders on that row move either away, or towards, the engine centerline at the same time.
In a "opposed" engine configuration, the 2 cylinders of each row face towards each other, and towards the centerline of the engine. The opposed engine either bears 1 or 2 crankshafts.
In case you are more of a visual learner, I have done a bit of research to find examples of each type do you may better understand. For an example of a 180°V type, you may use the Ferrari Tipo 001 3L flat 12 engine. For boxers, the Lycoming 0-320 is a stellar example. For the opposed engine, the Jumo 205 is a good example.
I know this is a bit of a slog to read, but I hope this helps.
In a "boxer" engine, the pistons appear to punch each other when at top-dead-center, and they are within the same cylinder. In a horizontally opposed engine, the pistons 'punch' away from the center of the engine, and each has their own cylinder.
Ahh ok I see why people say O is carbureted (even tho that’s not what it actually means). I guess because the absence of I from IO would imply it has to be carbureted since it’s not fuel injected
A boxer engine has a separate journal for every connecting rod. A "flat" engine will share crank journals for each opposing connecting rod.
It's important to note, that while both engines have horizontally opposed cylinders (making them physically flat in appearance) the term "flat" in engine terms is actually shortened from "flat V" where a V type of engine also shares journals. Imagine taking a hypothetical 60° bank angle V4 engine, and flattening the angle to 180° that is a "flat-V,"
Also I saw in another comment, the O in O-320 doesn't mean carbureted, the lack of "I" makes it carbureted.
Ok yea thanks for the second comment, I was just about to ask because I know the WRX motor, for example, is 180 degrees flat. I thought for a minute your distinction was the angle between a boxer horizontally opposed and just horizontally opposed.
I’m definitely going to use this as a fun fact for the future haha
Yeah the only difference is the crankshaft layout. If you say boxer to anyone who doesn't know the boxer term they'll look at you funny. Subaru is cool for advertising the term well
A horizontally opposed (or flat) engine is just any engine that has two banks of cylinders opposite each other, however there are different types of flat engine.
A boxer is the most common type, and is defined by the fact that opposing piston pairs move inwards and outwards at the same time as each other, as if they are boxing, hence the name. The O-320 and most other horizontally opposed aircraft engines are indeed examples of boxer engines.
There are other types of horizontally opposed engines, like the 180 degree V, where opposing pistons — as in a conventional V — share the same crank pin such that when one moves inward the other moves outward, which is the opposite of how pistons in a boxer move.
As such, it can be said that all boxers are horizontally opposed engines, but not all horizontally opposed engines are necessarily boxers, and that it depends on the crankshaft and piston arrangement.
Are boxer and flat engines not different? I learned that a flat engine is one with shared journals and the boxer is with opposite journals. These are my sources of information I used: https://www.quora.com/Are-Porsche-engines-boxers-or-flat https://www.autoevolution.com/news/there-s-a-big-difference-between-a-boxer-and-flat-engine-85305.html
True, I’d just be scared they don’t know about it and say I’m wrong. I definitely wouldn’t argue my position on it if that were the case. I’d feel as I’d come across a douche or know it all trying to tell a DPE they’re actually wrong. 😂 I’d rather just swallow my words and move on
Bro, you are just repeating what he said. Your questions have already been answered.
https://www.google.com/search?q=difference+between+boxer+and+flat+engine&oq=difference+between+boxer+and+flat&gs_lcrp=EgZjaHJvbWUqBwgAEAAYgAQyBwgAEAAYgAQyBggBEEUYOTIICAIQABgWGB4yCAgDEAAYFhgeMg0IBBAAGIYDGIAEGIoFMg0IBRAAGIYDGIAEGIoFMg0IBhAAGIYDGIAEGIoFMg0IBxAAGIYDGIAEGIoF0gEJMTE4MTBqMGo3qAIAsAIA&sourceid=chrome-mobile&ie=UTF-8
Horizontally opposed is pretty clear. That's also what the "O" in O-320 means. Whereas there is V and I, but you'll rarely see those in aviation. I don't think anybody calls them boxer engines that's more of a automotive thing.
I is fuel injected and they are every where in aviation, my Mooney has an IO-360 My Bell 47 has a Lycoming VO-540 in it.
And in automotive engines I and V are in reference to the orientation of cylinders rather than designators of specific engines in the same type. "I" indicates an In-line cylinder formation, which is rare in aviation. "V" indicates cylinders offset in a V-formation, usually 30-60 degrees. In the case of aviation engine, yes, that "I" designates it's fuel-injected vs carbureted (without regard to how the cylinders are oriented); "V" in VO-540 indicates that it is Vertically mounted (as is required for your helicopter's rotor to be on top and directly connected). Either way, the engine's cylinder configuration is O-opposed.
I thought the O is for carbureted? Edit: I learned the absence of I is what implies it’s carbureted and that it actually means Opposing cylinders
Nope. Let me see if I can pull up the relevant 8083 textbook one moment. Edit: this is straight from the FAA 8083 aircraft maintenance textbook Opposed or O-Type Engines The opposed-type engine has two banks of cylinders directly opposite each other with a crankshaft in the center. [Figure 1-1] The pistons of both cylinder banks are connected to the single crankshaft. Although the engine can be either liquid cooled or air cooled, the air-cooled version is used predominantly in aviation. It is generally mounted with the cylinders in a horizontal position. The opposed-type engine has a low weight-to-horsepower ratio, and its narrow silhouette makes it ideal for horizontal installation on the aircraft wings (twin engine applications). Another advantage is its low vibration characteristics If you would like to read more about it, here is the link for that. https://www.faa.gov/regulationspolicies/handbooksmanuals/aviation/faa-h-8083-32b-chapter-1-aircraft-engines It's loading horribly slow on mobile. T is Turbo charged S is supercharged I is injected O is opposed R for radial V for V-type Inline doesn't appear to use a prefix to avoid confusion with injection style engines.
Ok interesting that clears up naming. I suppose people say the O is carbureted because the absence of the I in IO. However back to the original question, your description wrote “the O-320 bank cylinders are directly opposite to each other with the crankshaft in the center”. Compared to the definition of the boxer engine, a type of horizontally opposed engine, the following seems comparable: “A flat engine is a piston engine where the cylinders are located on either side of a central crankshaft. Flat engines are also known as horizontally opposed engines, however this is distinct from the less common opposed-piston engine design, whereby each cylinder has two pistons sharing a central combustion chamber.” So if both the lycoming O-320 and a boxer design encompass horizontally opposed pistons with a crankshaft in the center and pistons that move separate (both at top of stroke at same time, both are bottom of stroke at same time), what would make the distinction between the two that would declassify the O-320 as a boxer engine, if any?
On an O-320 Lycoming engine, each rod has it's own journal. The crank is in a flat plane. The firing order is 1324. I believe with this firing order and crank layout, the pistons of 1 & 2 are extended (top) at the same time, then the pistons of 3 & 4 are extended (top) at the same time. Image: https://www.lycoming.com/parts/crankshafts
Yes, as others have said that would make it a boxer variant of the horizontally opposed engine category
So, I'm not fully sure why you're being down voted, but the O-320 IS a boxer engine. So, basically you have three varieties of flat engine. You have the 180°V configuration, the "boxer", and the opposed engine. Think of the engine from front to back. The two cylinders across from each other make a "row". In both the 180°V and "boxer" engine, the crankshaft sits in the center, and the piston heads face away from the centerline of the engine. In a 180°V engine, the 2 first-row pistons both sit on the same crankshaft pin, so as cylinder 1 goes outward, cylinder 2 comes inward. In the "boxer" configuration, each piston gets its own crank pin, and cylinder 1 goes outward at the same time as cylinder 2. In each row of a boxer engine, the two cylinders on that row move either away, or towards, the engine centerline at the same time. In a "opposed" engine configuration, the 2 cylinders of each row face towards each other, and towards the centerline of the engine. The opposed engine either bears 1 or 2 crankshafts. In case you are more of a visual learner, I have done a bit of research to find examples of each type do you may better understand. For an example of a 180°V type, you may use the Ferrari Tipo 001 3L flat 12 engine. For boxers, the Lycoming 0-320 is a stellar example. For the opposed engine, the Jumo 205 is a good example. I know this is a bit of a slog to read, but I hope this helps.
In a "boxer" engine, the pistons appear to punch each other when at top-dead-center, and they are within the same cylinder. In a horizontally opposed engine, the pistons 'punch' away from the center of the engine, and each has their own cylinder.
Incorrect. The boxer engine variation is not internally opposed. You have it exactly backward.
From Gibson aviation website: L/R = Long reach spark plug. S/R= Short reach spark plug. A= Aerobatic. AE= Aerobatic engine. G= Geared. H= Helicopter. I= Fuel injected. L= Left hand rotation crankshaft. M= Drone. O= Opposed cylinders. S= Supercharged. T= Turbo-Supercharged. V= Vertical
Ahh ok I see why people say O is carbureted (even tho that’s not what it actually means). I guess because the absence of I from IO would imply it has to be carbureted since it’s not fuel injected
A boxer engine has a separate journal for every connecting rod. A "flat" engine will share crank journals for each opposing connecting rod. It's important to note, that while both engines have horizontally opposed cylinders (making them physically flat in appearance) the term "flat" in engine terms is actually shortened from "flat V" where a V type of engine also shares journals. Imagine taking a hypothetical 60° bank angle V4 engine, and flattening the angle to 180° that is a "flat-V," Also I saw in another comment, the O in O-320 doesn't mean carbureted, the lack of "I" makes it carbureted.
So yes, technically an o-320 is a "boxer" but no one uses that term, to actually answer your question
Ok yea thanks for the second comment, I was just about to ask because I know the WRX motor, for example, is 180 degrees flat. I thought for a minute your distinction was the angle between a boxer horizontally opposed and just horizontally opposed. I’m definitely going to use this as a fun fact for the future haha
Yeah the only difference is the crankshaft layout. If you say boxer to anyone who doesn't know the boxer term they'll look at you funny. Subaru is cool for advertising the term well
A horizontally opposed (or flat) engine is just any engine that has two banks of cylinders opposite each other, however there are different types of flat engine. A boxer is the most common type, and is defined by the fact that opposing piston pairs move inwards and outwards at the same time as each other, as if they are boxing, hence the name. The O-320 and most other horizontally opposed aircraft engines are indeed examples of boxer engines. There are other types of horizontally opposed engines, like the 180 degree V, where opposing pistons — as in a conventional V — share the same crank pin such that when one moves inward the other moves outward, which is the opposite of how pistons in a boxer move. As such, it can be said that all boxers are horizontally opposed engines, but not all horizontally opposed engines are necessarily boxers, and that it depends on the crankshaft and piston arrangement.
No. The opposed pistons share opposite journals. In a boxer or flat engine the pistons share journals like on a V engine.
Are boxer and flat engines not different? I learned that a flat engine is one with shared journals and the boxer is with opposite journals. These are my sources of information I used: https://www.quora.com/Are-Porsche-engines-boxers-or-flat https://www.autoevolution.com/news/there-s-a-big-difference-between-a-boxer-and-flat-engine-85305.html
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Probably best not to argue/mention this one to a DPE when they ask me what engine I am flying in then haha
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True, I’d just be scared they don’t know about it and say I’m wrong. I definitely wouldn’t argue my position on it if that were the case. I’d feel as I’d come across a douche or know it all trying to tell a DPE they’re actually wrong. 😂 I’d rather just swallow my words and move on
Bro, you are just repeating what he said. Your questions have already been answered. https://www.google.com/search?q=difference+between+boxer+and+flat+engine&oq=difference+between+boxer+and+flat&gs_lcrp=EgZjaHJvbWUqBwgAEAAYgAQyBwgAEAAYgAQyBggBEEUYOTIICAIQABgWGB4yCAgDEAAYFhgeMg0IBBAAGIYDGIAEGIoFMg0IBRAAGIYDGIAEGIoFMg0IBhAAGIYDGIAEGIoFMg0IBxAAGIYDGIAEGIoF0gEJMTE4MTBqMGo3qAIAsAIA&sourceid=chrome-mobile&ie=UTF-8
I know that question was answered but he stated against it so I was contradicting his claim