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3D Printed Models - Big Thanks To Eric Harrell:
Straight-4 Model: www.thingiverse.com/thing:644933
Boxer-4 Model: www.thingiverse.com/thing:1643878

In this video we are going to be comparing inline four cylinder engines with boxer four cylinder engines, and talking about the individual advantages and disadvantages of each engine layout. We have a 3D printed EJ20 Subaru boxer engine, as well as a 22RE Toyota inline-four engine. We’ll start fairly basic and work our way through several different topics for each layout, including the four strokes, the firing interval and order, the vibrations of each layout, the packaging differences, the cylinder head differences, and finally a bit about the sound.

Looking at either layout, they’re both based on the same four strokes. Intake, compression, power, and exhaust. Both engines fire one cylinder for every 180 degrees of crankshaft rotation, but they have slightly different firing orders. On each engine, we can see cylinders one, two, three, and four. For the boxer engine, the firing interval is one, three, two, four, while on the straight four it’s one, three, four, two, so the order of the last two cylinders firing is switched.

On the boxer engine, you’ll notice the pairs of pistons move in and out together. This means that the primary forces when the piston reaches the top of the cylinder, as well as when they reach the bottom of the cylinder, are canceled out. On the inline four cylinder engine, it’s the same story, the primary forces cancel out as the pairs of pistons reach the top and bottom at the same time.

When we get into secondary forces, however, the engines begin to differ. Secondary forces are created due to the piston traveling faster at the top half of the piston than at the bottom half, something I’ll include a link to in the description for a video that breaks it down in great detail. What you need to know though, is that when the piston reaches the very top of the cylinder, or the very bottom, the secondary force points up or out from the piston. Now with the boxer engine, since the pistons point opposite each other, these forces are balanced out, resulting in a very smooth running engine. For the inline four, all of the forces point in the same direction, and thus do not cancel each other out, causing the engine to vibrate unless balancing shafts are used.

The boxer engine isn’t perfect, however, because the pistons do not perfectly align with each other, it creates a rocking moment which makes the engine want to rotate back and forth along the vertical axis. What’s fascinating, however, is that if you add two cylinders to either of these designs, whether it’s a boxer six or an inline six, you can perfectly eliminate all first and second order forces and moments. You might think the boxer six would have a rocking motion from the cylinder banks of three, but each bank of three cylinders cancels out the rocking motion of the other, unlike in a V6 configuration.

The other biggest advantage of the boxer engine is the low profile, which keeps the center of gravity low and thus reduces the amount of load transfer you have in the car during braking, cornering, or accelerating, which improves grip. With a lower center of gravity, you can also reduce body roll and choose to use softer springs. Additionally, in the event of a collision, it’s easier to position the engine so that it goes underneath the passenger compartment, rather than into the passenger compartment, for improved safety.

That’s not to say the inline four doesn’t have it’s own size advantages. Generally it’s a bit more compact, with only one cylinder head, and it’s not quite as wide as the boxer engine. This leaves more room for suspension geometry, and can also allow for a better steering angle, since the tires won’t have as much of an interference at full lock.

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Comments

    • ki jssn
      ki jssn

      Good luck changing the spark plugs on that boxer engine

      about 3 days ago
    • Aashish Bharadwaj
      Aashish Bharadwaj In reply to ki jssn

      I did on mine... Not that difficult

      about 2 days ago
    • Saw Greater
      Saw Greater

      22r & re were great engines for their time. 200,000 or more miles was a good engine back in the 80s. But let’s face the facts. They didn’t make any power, and still got less than 20mpg. If I’m driving around in a underpowered truck it better be getting at least 25mpg or better. Also there iron blocks and aluminum heads made for head gasket issues.

      about 4 days ago
    • alex montero
      alex montero

      Where can i buy this miniature? :)

      about 5 days ago
    • Lerigot
      Lerigot

      Question: On the boxer engine, why can't 2 pistons kinda the same cylinder so as one side fires, it compresses the other side?

      about 5 days ago
    • SakuraKiwi
      SakuraKiwi In reply to Lerigot

      Lerigot if they share a crank pin, it would not be a boxer but a flat-v.
      I do not know of a case where these are used as they vibrate like crazy and have no advantage over boxers (the money saved with the crankshaft would go with balancing shafts). I don’t even know if a working example was ever created.

      about 10 hours ago
    • Jason Karl
      Jason Karl

      The CAD game is strong in this one. One hell of a 3d print build

      about 10 days ago
    • Mark Wood
      Mark Wood

      Back in the 60s and 70s VW engines were the easiest to remove and rebuild on a chopping block. Today I own a Subaru outback legacy...07....head gasket regular maintenance...127.thousand ..garbage kept. Unless it dies on the road I'm keeping it till I die.

      about 11 days ago
    • 0zxu Dragon
      0zxu Dragon

      Differences of Boxer-4 and inline-4 engine sounds:

      Boxer-4: Brrrrrrruuuuuuuuuuummmmmmmmm

      Inline-4:
      ReeeeeeeeeeEEEEEEEEEEEEEEEEEEEE

      about 11 days ago
    • Alan Essex
      Alan Essex

      I WANT THAT 3D PRINTED ENGINE! NOW I HAVE TO BUY A 3D PRINTER. LOOK WHAT YOU HAVE DONE. ARE YOU PROUD?

      about 14 days ago
    • Dillon N
      Dillon N

      I own both a 2.5i(2018 outback) and a 22re (92 pickup) and I gotta say I love both of these motors. The 2.5i is a nice and very smooth motor. The 22re can be put through a world of torture though (wheeling and offroading). I dont think ide put my 2.5i through what my 22re has gone through. lol.

      about 18 days ago
    • Oscar
      Oscar

      Vw did use a boxer engine in the beetle in the old ones

      about 18 days ago
    • Oscar
      Oscar In reply to Oscar

      N the body was designed by porch

      about 9 days ago
    • Chaz Floyde
      Chaz Floyde In reply to Oscar

      The old beetle was created by ferdinand porsche

      about 18 days ago
    • PowerOf One
      PowerOf One

      2:47 dude, that flywheel on the inline 4. Like my 1973 Morris Marina..... :(

      about 29 days ago
    • Giordan Diodato
      Giordan Diodato In reply to PowerOf One

      *throws piano on the Marina*

      about 28 days ago
    • Reed Harston
      Reed Harston

      This video was just an excuse to drive that WRX. :)

      about 1 month ago
    • Conan
      Conan

      Minor correction for 0:50, on the 91 subaru's and later, they use two double-ended ignition coils on the top of the engine, with 3 wires coming from the computer to fire each coil two strokes apart. Cylinders 1 and 2 fire concurrently, same with 3 and 4, which of course means that the timing is off on that model.

      The yaw force as well is not a big deal and rarely measurable, particularly as the transmission helps prevent yaw movement, although it does contribute to eventual wear of the bearings throughout, albeit after some 25 years of use. This was how the prior engine failed in our 91, as while it still ran "quite well", the cams could slip to one side and cause the timing to shift, resulting in odd behaviour and a lack of power.

      about 1 month ago
    • Azif
      Azif

      And the FRS and GT86 ? they use Boxer and are toyota!

      about 1 month ago
    • Ben Davis
      Ben Davis

      My ‘79 air cooled Bosch fuel injected vw bus engine is my favorite gasser of all I’ve owned.

      about 1 month ago
    • vinn mcc
      vinn mcc

      I just never liked how the cylinder walls and pistons looked in a boxer when i took the engine apart. The wear on the bottom portion was unsettling.

      about 1 month ago
    • Denny D Speed
      Denny D Speed

      Boxer four leaks like a sift and less reliable.

      about 1 month ago
    • Dylan Burrows
      Dylan Burrows In reply to Denny D Speed

      300k on a 2004 forester x yes has some minor leaking on the gaskets. This was obviously not made on a Friday engine. Will be pulling it next year and doing a complete overhaul on it. Only vehicle I can say that beat this was my 1983 Honda hatch back 3 speed .. yes three full gears it was the deluxe model the rest only had two semi automatic. No couch but shifted. That car no major rebuild one timing belt had well over 500,000km on it. Body sagged out. Motor and trans still running like a champ. Averaged 35 mpg. 95hp 3 gears. Love my boxter engine. Easy to change the timing belt parts are not that expensive. But the body does rust a bit easier..

      about 1 month ago
    • Sebastian
      Sebastian

      Woa. Quite amazing effort for a video

      about 1 month ago
    • mcroadracer1
      mcroadracer1

      Well done. Excellent explanation

      about 1 month ago
    • Rezha Vikers
      Rezha Vikers

      Thanks for subtitle indonesian

      about 1 month ago
    • Christiaan Swanepoel
      Christiaan Swanepoel

      Ford Ranger has a 3.2L diesel 4cyl engine,so a 2.7 isn’t the biggest 4 cyl today

      about 1 month ago
    • Christiaan Swanepoel
      Christiaan Swanepoel In reply to Christiaan Swanepoel

      Korupt J plus the New Toyota is a 2.8 4 cylinder,so is that the biggest then?

      about 1 month ago
    • Christiaan Swanepoel
      Christiaan Swanepoel In reply to Christiaan Swanepoel

      Korupt J *My mistake,the Toyota outperforms a 5 cyl 3.2,just shows how good the toyota is

      about 1 month ago
    • Korupt J
      Korupt J In reply to Christiaan Swanepoel

      Ranger is a 5 cylinder 3.2 engine

      about 1 month ago
    • Alfian Zahrul Azam
      Alfian Zahrul Azam

      Judulnya pake Bahasa Indonesia..
      Setelah di play Ketauan UN bahasa Inggris gue jelek dah.. Hhmmmm えいごがむずかしですね

      about 1 month ago
    • Alan Smart
      Alan Smart

      Idolaku

      about 1 month ago
    • potatochobit
      potatochobit

      bro, I got a volvo it has FIVE cylinders!

      about 1 month ago
    • Jordan Broly
      Jordan Broly In reply to potatochobit

      Yes! Please talk about the odd engines!

      about 1 month ago
    • BeatThe D3viL
      BeatThe D3viL

      lol at that i-4's flywheel

      about 1 month ago
    • SR20DET_RX7
      SR20DET_RX7

      How about do the difference between a boxer, flat and horizontally opposed engines?

      about 1 month ago
    • SR20DET_RX7
      SR20DET_RX7 In reply to SR20DET_RX7

      +Michael Linner no it isn't.

      about 1 month ago
    • Michael Linner
      Michael Linner In reply to SR20DET_RX7

      The horizontally opposed engine is the same as a boxer.

      about 1 month ago
    • Soveliss Firemane
      Soveliss Firemane

      You ever go to type a comment out, intending it to be related to the video and once you get to the end you realize that you were ranting about something that has almost nothing to do with the topic except for maybe the last sentence in your comment? Yeah, that almost happened just now and I hate it when people do that, so I'm just going to say that I'd much prefer a flat four over an inline configuration. I love the sound my Impreza makes and I don't think there's anything more unique except maybe for rotaries.

      about 2 months ago
    • big doInk
      big doInk

      the boxer has a nice *R U M B L E* and the i4 sounds like crap at low revs

      about 2 months ago
    • big doInk
      big doInk In reply to big doInk

      +J Borg agreed, there are exceptions but we all love I6 engines so you didnt need to tell us that

      about 1 month ago
    • J Borg
      J Borg In reply to big doInk

      Audi's I4s sound pretty nice. Id really like to see more inline 6s though, its a really nice configuration.

      about 1 month ago
    • Paul von Hindenburg
      Paul von Hindenburg

      I've always wanted a boxer 8. But the price for them is high.

      about 2 months ago
    • Link Knight
      Link Knight

      2.7 litre inline 4 cylinder IS THE BIGGEST? NO NO NO. My father has a 4.4 litre inline 4 cylinder diesel in a huge backhoe he has. 1980 john deere.

      about 2 months ago
    • WBRos59
      WBRos59 In reply to Link Knight

      He's talking about current production engines.

      about 2 months ago