Different Flat & Boxer Engine Configurations Explained | Flat-Twin to Flat-16

Different Flat & Boxer Engine Configurations Explained | Flat-Twin to Flat-16
A flat engine is also a horizontally opposed piston engine with cylinders on either side of a central crankshaft.
Most flat engines use a "boxer" configuration because the movement of the engine's pistons resembles the action of a boxer's fists in the horizontal plane. However, unlike the boxer's fists, which both moves in the same direction, half of the 'Boxer' engine's pistons move in the opposite direction. Boxer engines have low vibrations since they are the only common configuration with no unbalanced forces, regardless of the number of cylinders.
Flat engines have been used in aviation, motorcycle, and automobile applications. They are now less common in cars than straight engines and V engines (for engines with six or more cylinders). They are much more common in aircraft, where straight engines are a rarity, and V engines have almost vanished except in historic aircraft. And They have even replaced radial engines in many smaller installations.
The advantages of flat engines are a short length, low center of mass, and suitability for air cooling.
The most common flat-twin engines are:
Flat-twin engines: A flat-twin engine is a two-cylinder IC engine with the cylinders on opposite sides of the crankshaft, where both cylinders move inwards and outwards simultaneously.
Flat-4 engines: A four-cylinder piston engine with two banks of cylinders lying on opposite sides of a common crankshaft. Most flat-four engines are designed so that each pair of opposing pistons moves inwards and outwards simultaneously. The terms "flat-four" and "boxer-four" are often used synonymously.
Flat-6 engines: It is a six-cylinder piston engine with three cylinders on each side of a central crankshaft, where each pair of opposed cylinders moves inwards and outwards simultaneously.
Flat-8 engines: A flat-eight engine is an eight-cylinder piston engine with two banks of four inline cylinders, one on each side of a central crankshaft.
Flat-10 engines: A flat-ten engine is a ten-cylinder piston engine with five cylinders on each side of a central crankshaft.
Flat-12 engines: A flat-twelve engine is a twelve-cylinder piston engine with six cylinders on each side of a central crankshaft.
Flat-16 engines: A flat-sixteen engine is a sixteen-cylinder piston engine with eight cylinders on each side of a central crankshaft.
--- Time Stamp --
00:00 - Introduction to Flat-Engines
01:43 - Types of Flat-Engines
02:01 - Flat-Twin Engine
04:42 - Flat-Twin Engine in Motorcycles
06:45 - Flat-4 Engine
11:00 - Flat-6 Engine
14:09 - Flat-8 Engine
16:16 - Flat-10 Engine
17:07 - Flat-12 Engine
19:55 - Flat-16 Engine
21:00 - Wrap Up
All images used in this video are under a creative commons license.
Watch our video on 'V' Engines: • Different 'V' Engine C...
Watch video on 'W' Engines: • Different 'W' Engine C...
Watch the video on Inline Engines: • Different "Inline Engi...
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[@TheEngineersPost]

The Difference between the Flat and Boxer engines: A “flat” engine is one with a 180-degree cylinder angle (which often lays flat in the vehicle) and is also correctly referred to as a “horizontally-opposed” engine. A Boxer engine will feature an individual journal for each connecting rod, 180 degrees apart from one another. This allows each pair of opposing pistons to mirror each other’s movements.

[@okami5029]

who else watching this was like "hol up they got a flat 16?!"

[@frygengrau823]

Yeah actually, the flat 16 in the video is from the Porsche 917

[@afoxwithahat7846]

I'm more amazed there's no flat 10 engines

[@Keterius]

@@frygengrau823 No? The 917 had a flat 12

[@Ramcharger85]

Hell yeah. 😂. Damn!

[@Camdenlw]

@@Keterius917/30 was tested with a flat 16

[@1888fel]

The boxer 8 is now my favorite engine for the noise. I fell in love with the flat engine configuration when I bought my 2022 BRZ, it sounds really nice and it feels responsive

[@TheEngineersPost]

Good choice!

[@DarthVader-1701]

The BRZ is basically an RX-7 but with a boxer instead of a rotary. Both Japanese cars but with German patented engines.

[@Ramcharger85]

Flat engines sound freaking amazing. But never knew they made a flat 10, let alone 12 or 16. Freakin sweet 😊

[@stevenmitchell6347]

Basically, the only real advantages of a V configuration with OHC and 6 or more cylinders over flat engines are width, oiling and, critically, aftermarket support. IMO as a retired Industrial Design Engineer and fabricator.

[@chrisjarmain]

I own an aircooled VW classic transporter. The noise is fantastic. Being its aircooled Is also unique from a mechanical perspective. So, whilst it may take up more space being a flat boxer, it is gained back with the lack of coolant components. It is a very simple engine. No timing chain or belt, and parts are VERY easily available. And because it is simple in design, it is open to vast modifications. Great for a motoring enthusiast. 😊

[@elias1162]

This is exactly what I'm looking for. Thanks a lot.

[@TheEngineersPost]

Glad I could help!

[@user-od5sl2jt7e]

Rotax, Subaru, Porsche, Alfa Romeo- we love you)

[@darylmorse]

Interesting video. Quite a few mixed up photos, but otherwise pretty well done.

[@wrenchg3954]

THIS VIDEO IS FREAKING AMAZING! IVE HAD A RELATIONSHIP WITH THE FLAT-4 SINCE I WAS A PRE-TEEN. NATURALLY MY FIRST CAR WAS A 69 VW BEETLE. THE REST IS HISTORY. I WASNT AWARE OF THE ABUNDANCE OF INFORMATION RELATING TO THE FLAT DESIGN. THEY'VE ALWAYS SEEMED TO UNCOMMON AND OBSCURE. DATED OR RARE. DIDNT KNOW HOW OFTEN MANUFACTURERS WENT BACK TO THE DESIGN

[@dorianleclair7390]

The WRX went to direct injection like the brz in 2015. And the exhaust manifold is no longer unequal length headers. So no longer has the boxer rumble. Supposedly more efficient going to equal length header.

[@mattperjes6173]

equal length headers are 9 times out of 10 more efficient because they have far better exhaust scavenging properties. The boxer rumble from the EJ’s occur because of the irregular pulses of the exhaust causing turbulence in the manifold.

[@georgewilkinson1068]

That "rumble" was made the old Subarus and the WRX a Subaru.

[@Omega_SM]

@@georgewilkinson1068 better being more efficient and powerful or having the engine noise but not the innovation and the performance?

[@mechguy8459]

Comprehensive guide on Flat Engine. Love it 💗

[@TheEngineersPost]

Glad you liked it!

[@oreisha9266]

Hermoso sonido el 8 cilindros, que locura 😍

[@thecelticprince4949]

Big thumbs up for the mention of Richard Pierce's motor.

[@tardstomper]

Subaru, damn you. I love those boxer style hamster wheels.

[@user-ll8gp8cg2o]

WOW appreciate you keep going love from pakistan

[@soundararajan2090]

Sir" really great explanation Master speaking . Thanks.

[@danishh3819]

thank you sir for information ❤

[@raunakdas4224]

Informative 👏 kudos to the editor

[@TheEngineersPost]

Glad you liked it

[@SmrazagilaniMohammadraza]

which is more durable for 4 wheel drive 4 to 6 in line or 4 to 6 boxer engines

[@Dustin1110]

EZ30 and EZ36 were actually available until last generation Outback in North America

[@ZepHoffman]

beautiful video, thanks

[@nickayivor8432]

Thanks 👍 Happy Christmas 🎄

[@joelejo1587]

Hello bro you kept you word. About engine. Nicely explain. Keep it up.

[@TheEngineersPost]

Thanks for watching

[@getthewin1046]

Very well explained 😘

[@TheEngineersPost]

Thank you 🙂

[@fadedsoul23]

So if I’m understanding this correctly, a flat engine (excluding 180 v engines) has pistons that don’t move simultaneously in pairs while a boxer does? Or is there more differences?

[@JeffCurtisIflyHG]

The way the author used the terminology, all these engines are flat engines, with horizontally opposed pistons. They can either be boxer or 180 V. In a boxer, each pair of horizontally opposed pistons have their own crank pin and each pair moves out together and in together. In a 180 V, the pair of horizontally opposed pistons share a single crank pin, as one of the pistons moves in, the other moves out and visa versa. For 2, 4, 6, 8, and 10 cylinder flat engines the boxer configuration is the better choice as it results in lower vibration. The way to imagine this is think of these motors as two 1, 2, 3, 4, 5, and 6 cylinder inline motors bolted to each other in mirror image. A single cylinder motor has poor primary balance, but as the video describes, in a boxer twin, the changes in momentum of one piston is balanced by the opposite movement of the opposing piston. Because the pistons have to be offset from each other along the crank due to the need for separate crank pin there is a rocking couple along the shaft as described in the video. An inline twin has good primary balance but a strong rocking couple and an uneven firing order. In a boxer 4 the rocking couple is almost completely eliminated (not completely because cylinders on one side are offset from those on the other) and even firing. If a flat 4 were built as a 180 V the rocking couple would that of the inline twin times 2, very bad. An inline triple has perfect reciprocating plane balance, even firing, but a rocking motion along the crank shaft. In a boxer 6 the rocking is almost completely eliminated. If a flat 6 were built as a 180V it would have the same rocking motion as the inline 3 times 2, so not as bad as a 180 V 4 but still, the boxer 6 is much better. Once you move up to 8 cylinder flat motors, the balance issues change, but firing order becomes an issue. An inline 4 has perfect primary balance. So while a 180 V 8 would have perfect primary balance, it would have the same secondary balance issue as an inline 4 and the piston firing separation would still be 180 degrees (always 2 pistons for each stroke). In a boxer 8, the crankshaft pairs of throws are separated by 90 degrees from each other, instead of flat like an inline 4. Look at the animation at 14:20. This enables perfect secondary balance and 90 degree firing separation. The boxer is still the better choice. An inline 5 has perfect reciprocating plane balance but a rocking motion along the crankshaft similar to the inline 3 but not as bad. A boxer 10 would nearly eliminate the rocking motion so probably the better choice still but maybe less compelling. An inline 6 has perfect balance. This is the case where a 180 V engine is the better choice as the crankshaft is simpler and the engine is slightly shorter due to less offset between banks required as a result of sharing crank pins. The animation of the flat 12 is a 180 V engine. Wikipedia has a good article on Engine Balance for further details.

[@imrancapricorn78]

you are the best one.

[@negeritopizza6103]

Man i wish there was a modern 5+ litre boxer 8 engine

[@hankyspanky1987]

Not to be rude but can't forget that in Gran Turismo 3 A-SPEC and Gran Turismo 4, sSbaru Impreza, 22B, Impreza STI and Mitsubishi Lancer Evo, and prototype used the boxer engines for rally races, the Suzuki Escudo Pikes Peak Version used a I think boxer 6 engine...going off what I was taught and learned from those 2 racing games (the best ones that ever came out for Playstation 2)

[@rocketbunnysti6344]

I love gran turismo

[@Ardonn]

Wrong. Evo's use an inline-4 and the Suzuki Pikes Peak cars use a V6. Only cars in GT 3 and 4 using boxer engines are Subaru and RUF/Porsche. You didn't read right or remember wrong, all information in GT games are correct. They definitely didn't write anywhere that an Evo would use a flat-4, they are a japanese company and know what engines japanese auto makers use better than foreign manufacturers.

[@adhammaher7717]

hey man please do a video of brake disks kinds

[@vastosbicycles8325]

for the two cylinder boxer engine like the BMW motorcycle engine, crankcase free breath causes a lot of pumping loss.

[@edonveil9887]

Would make sense to make it 2 cycle.

[@vastosbicycles8325]

@@edonveil9887 good point.

[@joshfoley8862]

Flat 4 in a 2006 Beetle? Rear drive? I wish.

[@h60memo]

I guess being an engineer doesn't mean one knows the difference between an old beetle and a new beetle.

[@alexjenner1108]

There are a lot of places where the video doesn't match the narration. For example 18:13 in 1964-65 the Ferrari 512 F1 with 1.5 L flat 12 ... meanwhile video switches to Ferrari with post 1990 high nose aero design.

[@trance9158]

Tucker automobiles are awesome.

[@dramirez6493]

11:02 Flat-6 Enigne what i win?? Haha nice video brother

[@primaht6180]

Why does engine (crank) not rotate opposite direction when it starts?

[@maxtuner5762]

Well When i crashed my 2004 subaru impreza The engine ended up beneath the car rather on my lap,so it's a win for me

[@MrTay675]

So realistic. Not really worth it until boxer 6 but once you do - yes you loose simplicity and weight compared to inline 6 but the lower weight center may give you a HUGE advantage looking for sports racing

[@fexploder3281]

12:08 I don't think this is a flat six engine so that's a flat 4.

[@Thom101]

rotary valves make boxer/flat configurations simpler and drops the part count (less to break). The Rotax brand is a good example.

[@narcissistinjurygiver2932]

why not repl the cyl heads with crankshafts and make an opposed piston engine?

[@chadkline4268]

Best engines ever. BMW boxers: best bikes ever 😎👍

[@droppindeuces6981]

Not really buying the 'too expensive to produce' argument (with regard to cylinder heads). Most V configurations require 2 heads as well. GM produced millions of examples of the Small Block V8.

[@micromymario23]

In fact, producing two simpler things is not necessarily more expensive than producing only one but more complex.

[@jasonmajere2165]

It does for inline 4, and V are just easier to package into a car.

[@mikestirewalt5193]

The Rotax you show has water-cooled heads. It's not purely an "air cooled engine".

[@yourordinarygamer6071]

Do the rotary engine please

[@karinaml.]

Can you make a video for mitsubishi 4g93t /GSR engine family?

[@TheEngineersPost]

I surely will do it.

[@NorthWay_no]

So basically the flat engine world is screaming for support from FreeValve to massively shrink the needed space. The explanation was that the boxer fires opposite sides 360 degrees apart,, but are there no configurations where both sides fire simultaneously?

[@benedictgorospe5246]

This is the literal version of she purs like a kitten Edit: sorry i forgot to put the time 8:50

[@Lancair320]

The Rotax engine you showed for the aircraft flat 4 is both air and water cooled so you’re carrying heavy water. You would have been better off showing a Lycoming or Continental 4 cylinder. They’re purely air cooled.

[@jaumebaldevell6137]

Motor porsche 917 y ferrari motor V 180° no .boxer cateto

[@robertmyatt9177]

Er the Porsche 918 has 4 not 6 cylinders

[@nickt8972]

Correction...Ferrari 12 cyl. BOXER engine for F1 was (312) was introduced in 1970 in the 312B, not in 1975 in the 312T.

[@user-sy1ed9ex5m]

It's flat, not boxer. It have common rod journals for the opposing pistons, and not separate as a true boxer.

[@shariqhasan6220]

Ok so based on the sound of the engine at 4:27, its safe to say all cars in Gran Turismo 1 had flat twin engines 😂😂😂

[@EJ20555]

ｲｴｴｴｴｴｴｴｴｴｲｲｲ水平対向エンジンﾀﾞｱｱｱｱｱｱｱｱｱｱｱ

[@jairepp]

you forgot to ad alfa romeo flat 4

[@palashchoudhury5565]

180° Flat 4 OHV Engine

[@aadaminda5717]

❤️❤️❤️❤️❤️❤️❤️❤️❤️

[@khushbuparikh2825]

Made it water to work yo engine no required off fuel work for you khushbu girishchandra parikh

[@khushbuparikh2825]

Made it air to work engine no required off fuel work for you khushbu girishchandra parikh

[@emilcsollak695]

V 180 ° pistons

[@user-sy1ed9ex5m]

No mention of the Alfa Romeo boxer 4?

[@fabrisoto]

👏🏽👏🏽👏🏽👏🏽👏🏽👏🏽👏🏽

[@denverbulsao8142]

6 cylinder

[@marcotravaglini5747]

Interesting. But You've forgot to mention Lancia Flavia 1.5, 1,.8, and 2.0 liters flat Boxer fours. They were lightweight alloy engines developed in the '60s.

[@worldhello1234]

@13:11 the 914/6 is 4 times as expensive as the VW flat 4 914 counterpart.

[@tomster7574]

The most common flat engines are every Number of cylinder engines? Except a single cylinder which can’t possibly be a boxer engine nor even flat.

[@trance9158]

Porsche rules!!!!

[@bulentbuyuk]

14 silindir racig turbo

[@patrickcorcoran1718]

This would have been so much better without the computer generated voice and sloppy image use.

[@pauloguerreiro6487]

He didn't mention the Testarossa, which had a flat 12

[@nathangrant104]

Probably because Ferrari didn't use a true boxer engine in that car.

[@darrenlyddieth5770]

O Alpha Romeo, Alpha Romeo, wherefore art thou Alpha Romeo?

[@h60memo]

That bothered me also

[@almelling6699]

Those engines shown are Boxers not flat ,,,flat is the opposing pistons on the same crankpin. Different.

[@rossbrumby1957]

The flat 12 wasn't a boxer, as the demo video showed- same crankshaft as a V12.

[@martinb.770]

Rather superficial overview. The difference between V180° and why there are barely Boxers beyond 6 cyl, doesn't get analyzed, the 2 mio Alfas (Sud, 33, 145/146) don't even get mentioned, the Citroen GS get just hinted, the evolution of the beetle/356/911 engine not even scratched, let alone the aspect of turbos/biturbo in Boxers, but the same "pros" and "cons" repeated by a mecha voice for any cyl nr.

[@javigar133]

Two minutes in and I am impressed, he knows 2, 4, 6, 8, 10 lmao

[@user-km3dj4bu3p]

thank god for BRZ

[@mmd8488]

ボクサーエンジンを語るなら、水平対向とⅤ型１８０度の違がいを理解して無いと駄目と思う。

[@kitsune1594]

Soviet T-64 tank uses 5 cilinder opposite 5TD engine.

[@dudley7540]

No H-16?

[@mikeglenn3333]

Volkswagen lost a lawsuit in the 50's to Tatra over the air cooled engine designs

[@elgronch8673]

aparently you forgot about Tatra 11 (1923-1927)

[@wernerschwarz7596]

The Porsche 718 GTS does not have a flat-6. It hast a flat-4. so sad