BOXING DAY: 50 Years of the Subaru Boxer Engine

Lead vehicle designer Shinroku Momose “was not fussy about the engine,” recalls Motomitsu Honda, who worked in Subaru engine department in 1966. Momose merely “presented the required dimensions and performance and said that any type of engine would suffice providing [it] met those conditions.” And so, 50 years ago, the Subaru boxer engine was born. 

The Subaru 1000 debuted in 1966, the automaker’s first foray into the regular, non-kei car market. Until then, Subaru’s main product had been the ladybug 360, and while it had been perfect for Japan at the time, it wasn’t a car could be taken seriously in the rest of the world. Aside from a few early concepts that never made it to production, this would be Subaru’s most aggressive attempt yet at entering the league of passenger car giants such as Toyota and Nissan.

It was decided early on that the car should be front-wheel-drive. That may be the default format for mainstream cars now, but back in 1966 this was pretty advanced stuff, and the best sellers would still be rear-wheel-drive for at least another couple of decades.

Momose laid out four simple criteria:

  • The differential gear was to be located in the center of the car body in order to minimize the drive shaft operating angle.
  • The engine height was to be low in order to keep the center of gravity down and increase flexibility in body design.
  • The front overhang needs to be short.
  • Vibration should be reduced in order to enhance the ride quality.

Honda-san’s team considered three options, including a transversely mounted inline-four and a narrow-angle V4. That’s right. In an alternate universe, your beloved blue rally beasts could’ve been rocking the same engine configuration as a Saab Sonnet.

Instead, they went with option three. There are many ways to describe it — horizontally opposed, flat-four, a 180-degree V4 — but the simplest name was boxer, for the way its pistons were locked in a permanent sparring match like the fists of two prizefighters.

“In FWD development at that time, the greatest problem was the drive shaft joints,” Honda said in a company publication years later. “In order to avoid placing load on the joints, it was necessary to extend the drive shafts and make them equal length. However, this was difficult to achieve with the transversely mounted in-line four-cylinder engine.”

Targeting cars like the Mazda Familia and ubiquitous Nissan Sunny, the team decided on a 1.0-liter displacement. The result was the EA-series engine, generating 55 PS and 56 lb-ft of torque with a impressive-for-the-era 9.0:1 compression ratio. Despite the fact that aluminum was 14 times more expensive than iron at the time, engineers used it for the crankcase to reduce weight.

Other advantages presented themselves, too. The side-to-side motion of the pistons and the inherent balance in their motion — in which pistons on opposed sides of the crank canceled each other’s momentum out — reduced vibration. The low, wide mass provided a superior center of gravity compared to a vertical cylinder layout. Its shape gave it an advantage with cooling efficiency as well, and the centrally-located carb provided even fuel distribution to all cylinders.

To top it all off, the boxer’s placement over the front axles with 58 percent front-biased weight distribution gave the 1000 great hill-climbing abilities in northern Japan’s snowy winters. This led to Subarus becoming well known throughout the country for first-rate low-traction performance, which in turn led to a chance encounter that turned Subaru into masters of all-wheel-drive.

The EA-series boxer persevered even as the 1000 evolved into the Leone, and over the decades increased displacement from 1.1 to 1.2, then 1.3, 1.4, 1.6 and eventually the 1.8 liter EA82. Meanwhile, Subaru continued to develop the EA from an OHV design with pushrods to single overhead cams. Some incredibly rare aftermarket DOHC heads made for aircraft even exist.

With the changing technology from the 1960s to 1980s, the EA came in just about every fuel delivery style imaginable — single carb, twin carb, throttle body fuel injection and port injection. The EA engine even supported Subaru’s first push into turbocharging. It didn’t power its last Subaru until the end of third-gen Leone production in 1994.

The legacy of the EA would be improved upon come the introduction of the Legacy. While Subaru would keep the longitudinal boxer layout they would completely rework the internals allowing for even the basic 2.2-liter EJ engine to put out more power than powerful EA82 Turbos of the later Leones and Alcyones (GL-10 and XT, respectively).

The EJ series came to define modern Subaru performance, powering everything from grocery getter base model Foresters to — in DOHC, 16-valve turbocharged and intercooled guise —  rip-roaring WRX and STI rally racers. The ultimate street legal version was the closed-deck EJ22G, found in the limited-production Impreza STi 22B. On paper, it generated 276 horsepower under the Gentleman’s Agreement era, but was actually something closer to 300.

Even lesser EJ motors can be found — and heard, with their distinctive unequal header burble — in suburbs across the country as the performance engine of choice among young gearheads. If American Graffiti took place today, Harrison Ford would be far more likely to pull up at a red light beside a boxer-powered Subie in WR Blue than a 427-equipped yellow ’32 Ford. All the while, the engines are so closely related that an EJ engine will fit in the home of an EA with minimal issue.

Today, the last of the EJ family is being phased out in favor of the modern FB-series engines. While time will tell if they will be as fondly remembered, rather than switch to a more conventional design, it continues Subaru’s tradition of the boxer that Honda-san’s team started a half century ago. Did they know in 1966 that the engine they’d selected would become the cornerstone for all modern Subarus in 2016 and beyond?

In 1975, Hideshige Gomi had just finished federalizing the EA boxer to pass the US’s new and extremely stringent emissions standards. “The horizontally opposed engine, made by my mentors, includes merits such as low vibration and noise, excellent rotation balance, and superior cooling efficiency,” he said in an interview with Cartopia magazine.

“I believe that maintaining and further improving on these merits is a step in the right direction for solving the problems of exhaust emission. My basic philosophy is that strong points should not be abandoned and simple designs are good.” In other words, if it ain’t broke, why fix it? “I am confident that our horizontally opposed engine has great potential in the future,” Gomi-san concluded. Here’s to another 50 years.

Images courtesy of Subaru.

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10 Responses to BOXING DAY: 50 Years of the Subaru Boxer Engine

  1. Scotty G said:

    Long live SuBARu! I have 341,800 miles on the 1997 Outback with a 2.5 boxer and hopefully it has many more to go. Thanks for the great history on these great engines!

  2. Mike RL411 said:

    The SAAB Sonnet V4 was actually an Industrial Ford V4 engine.

  3. Tom Westmacott said:

    This is a fantastic article, I was really interested to learn about the reasoning that led to the initial adoption of the boxer four – basically, wanting to go FF when it was in its infancy.

    Coming to these cars in the nineties as I did, it was easy to see Subaru’s distinctive drivetrain as a logical choice for a 4wd performance car; less obvious why they originally chose it half a century ago. Now I know.

    The willingness to stick with the boxer, keeping onto its strong points, rather than giving up and joining the herd with an inline-four, is commendable and gives Subaru a character that is genuine and engineering-based, rather than bestowed by the marketing department.

  4. emuman said:

    A boxer motor is not a 180° V engine, the boxer has one crankpin per cylinder.
    And the engine used in the Saab was from the Ford Taunus.

  5. PallySuby said:

    well my 2001 Forester limited has done nearly 370 000kms and has even been to Cape York in Australia’s far north Queensland and has done some decent offroad, with a duel range AWD system the low range makes it a very capable car offroad, its good on fuel its parts are fairly cheap. the EJ202 in it could always use abit more poke for every day driving but I find in low range 1st it can climb some pretty steep terrain.

  6. Punto8 said:

    Maybe I am wrong here but isn’t the “Subaru Boxer Engine” just a Japanese version of the aircooled VW engines? If so, why not say that Subaru was an innovator and not that they birthed this engine? You could make an arguement for every engine but the “boxer” engine like the rotary is very unique and both are German derived.

    • Mark Newton-John said:

      Not even close. You simplify the fact the Volkswagen motor designed by Ferdinand Porsche and the Subaru motor are both flat fours. You might a well have said all V-8s are Ford copies.
      Don’t be so Eurocentric.

    • They are completely independently designed engines. However swapping an EJ into a vw platform is not unheard of.

      The most notable difference of the VW boxer vs the Subaru boxer would be air cooled vs water cooled though.

  7. Negishi no Keibajo said:

    Very few automotive engines make their way to aircraft, but the Boxer has had pretty good success in Amateur Built Experimental Aircraft. It’s enough of a success that there’s a following and a small market for supporting them. It’s one thing to trust an engine on a freeway. It’s another to trust your life to it climbing out at a few hundred feet.

    Fuji Industries, as you may know, traces its roots back to the Nakajima Aircraft Company of WWII fame (They built fighters, but no, they didn’t make the “Zero”. Mitsubishi did.) and even supplies the Boeing Aircraft Company with components today. The first time I was fascinated with Fuji was seeing the Rabbit Scooters running around Japan in the 60’s.

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