Different Flat & Boxer Engine Configurations | Explained

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

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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.

[fel]

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

[Ramcharger]

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

[okami]

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

[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. 😊

[stevenmitchell]

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.

[odsljte]

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

[Iluzen]

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

[dorianleclair]

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.

[darylmorse]

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

[thecelticprince]

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

[mechguy]

Comprehensive guide on Flat Engine. Love it 💗

[oreisha]

Hermoso sonido el 8 cilindros, que locura 😍

[Dustin]

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

[fadedsoul]

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?

[hankyspanky]

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)

[joelejo]

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

[vastosbicycles]

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

[wrenchg]

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

[joshfoley]

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