The horizontally-opposed engine is a design icon. Damien O’Carroll shares five facts about it.

Karl Benz invented it

That’s right, the same bloke who is largely credited with inventing the modern motorcar also came up with the horizontally-opposed engine.

Benz was awarded a patent for the first horizontally-opposed engine – a two-cylinder in the boxer layout – in 1896 and built his first one in 1897.

He would use it in road cars such as the Benz Phaeton and the brilliantly-named Benz Mylord, as well in a 12-seater bus. He even built a 5.4-litre flat-four for use in the 20hp racing car from 1900.

Production of the ‘‘contra engine’’, as Benz called it, ended in 1902 and Benz never used a boxer engine again.

Not just cars

It won’t surprise bike fans that the horizontally-opposed engine wasn’t just a car thing – BMW Motorrad has a long history of using them, and while the Honda Goldwing is a famous example, many other bike makers have used horizon tally opposed engines since Benz invented the concept.

But the design has also been used in aeroplanes, including the most famous one of all time (in this part of the world) – the Pearse monoplane in which New Zealander Richard Pearse arguably achieved flight two years before the Wright Brothers.

During World War II, German company Reidel used a two-stroke flat-twin as a starter motor for its jet engines.

Not just Porsche and Subaru

Porsche and Subaru have stuck faithfully with the horizontally opposed engine for decades, but they aren’t the only carmakers to flirt with the layout.

Ford, Lanchester and Jowett all toyed with flat twins in various models in the engine’s early days, and Tatra famously used flat-twins and flat-four in its cars.

The Tucker 48 and Chevrolet Corvair both used flat-sixes and, of course, Volkswagen launched its entire company based on an aircooled flat-four.

Ferrari also used flat-12s, but they weren’t the ‘‘boxer’’ layout of most of the other engines (pistons have separate crank pins), rather they were ‘‘180 degree V’’ engines (pistons share a crank pin).

Flat-10s never made it

While Porsche used flat-eight engines in racing cars and Ferrari used flat-12 engines, no flat-10 engine ever made it into production.

The only one that made it to prototype stage was a Chrysler flat10 that was part of an abandoned programme for a family of modular engines to replace the Turbo-Air 6 flat-six engine.

Horrifyingly, the flat-10 was intended for the Corvair that had enough handling issues with a flatsix located in the rear and swing axle rear suspension.

However, it never got past the prototype stage where one was fitted to – wait for it – a 1962 Impala that had been converted to frontwheel-drive.

Flat-16s never worked

Poor Lotus, it got caught up in two disastrous attempts to make a flat16 engine for Formula One.

Legendary British engine maker Coventry Climax tried to make a flat-16 engine for Lotus in 1966, but failed spectacularly, with a huge number of design issues that the company simply ran out of time to fix.

Lotus was forced to run with BRM’s equally disastrous and massively overweight H16 engine (two flat-8s on top of each other with a common output shaft) in 1966 that saw it have a winless season, while Coventry Climax’s failure caused massive damage to its reputation and saw it drop out of F1 entirely.