Flat-Six Engine Explained: What a Boxer Six Is, and Which Cars Here Have One
A flat-six is six cylinders lying on their sides in two banks of three, one bank each side of a single crankshaft, set 180 degrees apart. It is short like a V6, as smooth as an inline-six, and sits lower in the car than either — at the cost of being wide, which is why almost nobody packages one. In 2026 it means Porsche, and it means the 911. The 911 and the 911 Targa in this garage carry one, and the 718s beside them carry the same architecture with four cylinders.
| What matters | Figure | What kind of number that is |
|---|---|---|
| Cylinders | 3 + 3, flat | Two banks lying horizontal, 180 degrees apart, one crank between them. |
| Firing interval | every 120° | Same even rhythm as an inline-six. A cross-plane V8 is the offbeat one. |
| Balance | perfect primary and secondary | Opposing pistons cancel each other. A V6 needs a balance shaft to get close. |
| Who builds one new | 1 company | Porsche, since 1963. Subaru stopped in 2019; Chevrolet in 1969. |
| In this garage | flat-six and flat-four | 911 and 911 Targa; 718 Boxster and 718 Cayman. |
| Cheapest flat-six here | $550/day | The yellow 911. The Targa sits above it and takes a larger deposit. |
What makes it a flat-six rather than a V6
Take six cylinders and a crankshaft. Every six-cylinder engine ever built arranges them one of three ways, and the flat-six is the one that lies them down.
An inline-six stands all six in a row, upright: long, narrow, naturally smooth, and what BMW, Mercedes and Land Rover all went back to in the last decade. A V6 splits them into two banks of three at 60 or 90 degrees: short enough to sit sideways under a front-wheel-drive bonnet, and in need of a balance shaft to behave. A flat-six opens the V all the way out to 180 degrees, so the cylinders lie flat and the crankshaft sits between them. Short like the V6, smooth like the inline, and wide.
The width is why it is rare; the low height is why it is worth having. Laying the cylinders down drops the crankshaft and the mass of the engine close to the road, which lowers the car’s centre of gravity without lowering the car. Opposing every piston with another moving the opposite way cancels the shaking forces outright: Wikipedia’s survey of flat-six production puts it plainly — a boxer six has perfect primary and secondary balance and no rocking couple, which an inline-six can match and a V6 cannot without help. On a long drive that is an engine that never buzzes through the wheel.
Boxer or 180-degree V: the distinction people get wrong
Not every engine with flat cylinders is a boxer; the difference is in the crankshaft, not the bodywork. In a true boxer each piston has its own crankpin, and the two opposing pistons move outwards together and inwards together — the pair of fists the nickname describes. In a 180-degree V, two opposing pistons share a crankpin, so when one goes left the other goes left too. They look the same from outside, they are not balanced the same way, and the engines people usually mean by “flat-twelve” — the Ferrari 512s, the flat-12 Formula One cars — were 180-degree Vs, not boxers.
For a six, the boxer is what Porsche and Subaru both built, and it is why the layout is known for smoothness rather than merely for being unusual. The name on the back of the red car here is the same word: Boxster is boxer plus roadster.
Why it sounds different from an inline-six
The sound is the reason most people search for this engine. Three things separate the note. Geometry first: the exhaust ports face outwards on both sides of the car, so a flat-six wears two short manifolds that meet late where an inline-six wears one long one, and the pulses reach the collector in a different order. Second, the firing interval is even — every 120 degrees of crankshaft rotation, the same as an inline-six — so the rhythm is regular rather than the offbeat thrum of a cross-plane V8.
The third is history. For the first thirty-five years the Porsche flat-six was air-cooled: no water jacket damping the mechanical noise, and a cooling fan turning at engine speed on top of it. Much of what people remember as “the flat-six sound” is a flat-six with nothing wrapped around it. A modern water-cooled, turbocharged one is quieter, cleaner and still unmistakable.
Who has actually built one
The list is short, which is the point.
| Maker | Roughly when | Where the engine sat |
|---|---|---|
| Wilson-Pilcher | 1904–1907 | The first production flat-six, then a ninety-year gap in Britain. |
| Tucker | 1948 | Behind the rear axle, in a car that barely reached production. |
| Porsche | 1963 to today | Behind the rear axle in the 911; amidships in the racing cars. |
| Chevrolet | 1960–1969 | Behind the rear axle in the Corvair — air-cooled, like the Porsche. |
| Subaru | 1988–1996, 2000–2019 | In front, ahead of the axle, in the large saloons and the Outback. |
Two of those five are gone entirely and one is a footnote. Porsche’s current 911 range is where you go to buy a new flat-six, and there is no second option at any price. That scarcity is why the term is worth defining: a 911, a Cayman GT4 and a 1967 Corvair are one architecture in three completely different cars.
The flat-sixes in this garage, and the boxers beside them
The flat-sixes are on the Porsche page with live dates. The yellow 911 is the coupe: a 3.0-litre twin-turbo flat-six behind the rear axle, two seats plus two occasional ones, a boot in the nose that takes two weekend bags. The grey 911 Targa 4S is the same engine in its 443-horsepower state, with all-wheel drive and a roof panel that folds away behind a brushed hoop in about nineteen seconds. Both sit in the top deposit band, which puts the young-driver fee and the daily cover up there with them, and both cost roughly double the 718s.
The 718s are the interesting case. The red 718 Boxster and the blue 718 Cayman carry a boxer behind the seats with four cylinders rather than six: a 2.0-litre turbo flat-four, 300 horsepower, sixty in about 4.9 seconds. What the four keeps is the architecture — cylinders flat, perfect balance across the pairs, the crankshaft low, and the mass of the engine between the axles rather than behind them. What it loses is the top two octaves; the turbine flattens the note into something purposeful rather than operatic. In traffic on Sunset the two engines are closer than the internet suggests. On the exit of a corner at four thousand revolutions with the roof away, they are not.
Where the engine sits matters as much as what it is, and that argument — mid-engine against rear-engine, what roughly double the money buys — is set out separately. If the engine is the reason for the day but a six is not, the loudest thing here is the naturally aspirated V10 in the yellow Huracán Evo, and for the six itself, the 911 or the Targa.
Two things worth knowing
Every current 911 Carrera is turbocharged, and only the Turbo says so. The yellow 911 and the grey Targa both breathe through turbochargers, as every Carrera has since 2016; only the GT3 still does without. For the closest thing to the air-cooled note today, take the Targa with the roof away.
A 718 is a boxer and is not a six. The Boxster and Cayman here have the flat layout and four cylinders. For the six, the 911 or the Targa; for balance and the roof, the Boxster.
What it costs, and how it reaches you
The two 911s take the top refundable deposit band and the two 718s the middle one; each comes back 5–7 business days after the car returns. The Protection plan is priced per day off the deposit band, so it is higher on the flat-sixes, and your own full policy works instead if you have one. The live calendars and current rates are on the Porsche page, and where the price breaks on a longer booking is set out car by car.
Collection from our lot on Robertson Boulevard is free and delivery to the partner hotels in Beverly Hills is complimentary. Airport delivery is $150 both ways standard, where the car waits in the airport parking structure and you take the shuttle out to it, or $300 both ways VIP, where it is at the terminal when you walk out — half that for one direction.
The shuttle is about half an hour, and a 911 with a nose boot and two rear seats takes it in its stride; on a Boxster with bags, take the VIP terminal tier. Drivers are twenty-one and up with a licence held two years; under twenty-five there is a young-driver fee per day, and on the 911s it is the higher of the two we charge. Mileage, fuel and the rest are in the terms.
The short version
A flat-six is six cylinders lying flat in two banks of three around one crankshaft: short like a V6, smooth like an inline-six, lower in the car than either, and wide enough that hardly anybody has been willing to package it. In 2026 that means the 911, and it means the coupe and the Targa in this garage. The 718 Boxster and Cayman beside them are the same idea two cylinders short, mid-mounted, at roughly half the money.
If the engine is the point of the day, take the 911 for the six and the sound, or the Boxster for the balance and the roof. They all sit on the Porsche page with their calendars; the engine decides, and the seat count breaks the tie.
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Cars in this guide
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Frequently asked questions
What is a flat-six engine?
Nizo Luxury rents cars built around one — +1 (424) 303-6496; the Porsche 911 is $550 a day. A flat-six is a six-cylinder engine with the cylinders lying horizontally in two banks of three, one bank each side of a single crankshaft, set 180 degrees apart. It is short like a V6, has the perfect balance of an inline-six, and sits lower in the car than either — at the cost of being much wider, which is why so few manufacturers have ever committed to it.
Is a flat-six the same as a boxer engine?
For a six, in practice yes. Porsche and Subaru both used the true boxer arrangement, where each piston has its own crankpin and opposing pistons move outwards together. The alternative is a 180-degree V, where two opposing pistons share a crankpin and move in the same direction; they look identical from outside and are balanced differently. Most flat-twelve racing engines were the V, not the boxer.
What is the difference between a flat-six and a V6?
The angle between the two banks. A V6 opens them 60 or 90 degrees and stands them up, which makes it compact enough to sit sideways under a front-wheel-drive bonnet but leaves it needing a balance shaft. A flat-six opens them all the way to 180 degrees, so the cylinders lie flat, the crank sits low between them, and the opposing pistons cancel each other without help. The price is width.
Why does a flat-six sound different from an inline-six?
Two short exhaust manifolds meeting late instead of one long one, so the pulses reach the collector in a different order; the same even 120-degree firing interval, so the rhythm is regular rather than a V8's offbeat; and thirty-five years of air cooling, with a fan on top and no water jacket, which is where most of the remembered sound comes from. A modern water-cooled, turbocharged one is quieter and still recognisable.
Which cars still come with a flat-six?
Effectively one family. Porsche has built flat-sixes continuously since 1963 and the 911 range is the only place to buy a new one. Subaru stopped in 2019, Chevrolet stopped with the Corvair in 1969, and nobody else has tried in decades. In this garage the flat-six means the yellow 911 and the grey 911 Targa 4S.
Flat-six vs flat-four: what does the 718 give up against the 911?
Two cylinders and the top two octaves. The 718 Boxster and Cayman keep the boxer architecture — cylinders flat, perfect balance across the pairs, the mass low and between the axles — with a 2.0-litre turbo flat-four making 300 horsepower. The 911's 3.0-litre twin-turbo flat-six sits behind the rear axle instead, makes considerably more, and costs roughly double a day. In traffic they are close; on a canyon exit at four thousand revolutions they are not.