• Sep 30, 2006
The design of the horizontally-opposed engine has a myriad of benefits. One of the most common is its compact design, which allows the center of gravity to be lower in the host vehicle. Additionally, since the boxer's pistons cancel out much of the vibration, the rotational balance is second to none. Both of these advantages will lend themselves to the advent of the first boxer diesel, which will find a home within a variety of Subaru models in Europe and possible even here in the States.

Hiroyuki Ikeda, Subaru Europe's President, announced at the Paris Motor Show that the development of the H4 turbo-diesel boxer is almost complete. The design, pictured above, reveals two interesting tidbits: first, the turbo, which is traditionally housed towards the passenger side firewall on most Subarus, will be moved south of the crankshaft to retain the boxer's low center of gravity. Second, the new DOHC diesel will be outfitted with a timing chain, currently only seen on Subaru's H6 engines, and will be the first H4 so equipped.

If one of Subie's diesels does make it to this continent, expect it to reside under the hood of the new Forester.

[Source: GizMag via Straightline]


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  • 42 Comments
      • 8 Years Ago
      #14, according to MotorTrend, the Subaru Legacy GT Spec B has a 57/43 weight distribution. The MazdaSpeed 6 that they compared it to has a 60/40 distribution and has an inline 4. So there appears to be little difference between two comparable cars in terms of weight distribution despite having different powertrains. Not exactly a big difference in terms of "nose-heaviness."

      True, they're not compact (and it doesn't seem like anyone is asserting that they are), but there are benefits to boxer engines. If you compare the Tribeca to the X5 there is a 1.5" difference in their centers of gravity. And yes, it is the Subaru which is closer to the ground.


      http://www.motortrend.com/roadtests/sedan/112_0602_midsize_awd_sedan_comparison/specs_price.html
      http://www.subarunews.net/news/news20060722.htm
      • 8 Years Ago
      "2. i wasn't aware subaru still sold cars which were FWD in america?"
      They don't, the entire Subaru lineup of vehicles sold in the U.S. has AWD standard. Not sure what #1 is talking about.
      • 8 Years Ago
      I've driven a bunch of boxer engine cars including Subarus and I've never found them to be that smooth running.
      • 8 Years Ago
      2001 Outback with 75k miles, no problems other than trivial quirks that were quickly fixed under warranty (as in, nothing ever stranded the car, or caused inconvenience).
      • 8 Years Ago
      A four cylinder Lycoming engine (which has EXACTLY the same balace charactristics as the Subaru boxer) is balanced for both
      force and torque couples (moment) for first-order vibration

      The same engine is balanced for force of both the primary and
      the secondary components of second-order vibrations.

      It is balanced for the moment of the primary component of the
      second-order vibration.

      It is NOT balanced for the moment of the secondary component
      of the second-order vibration.

      The opposed aircraft four cylinder engine tries to rock
      clockwise and then counter-clockwise (when viewed from above)
      with each full revolution of the crankshaft.

      For the curious, an inline four engine has the exact same problems with
      secondary vibrations as our opposed four-cylinder aircraft engine. However,
      because the cylinders are inline vs. opposed it is unbalanced for secondary
      forces not moments. Instead of trying to rock back and forth the inline
      four-cylinder engine tries to "hop" up and down on its mounts.
      The addition leverage provided by the opposed cyl config against the torsion twist tends to help dampen out the vibrations. So to end the silly argument , yes a boxer has inherently better balance than an inline or V config, the remainig vibrations are simply presented in a different manner. A boxer just "feels" different. I prefer them personnaly.
      • 8 Years Ago
      i wasn't aware subaru still sold cars which were FWD in america?
      • 8 Years Ago
      If they do bring it over here, we'd probably see it in all of the subaru line. I'm just hoping in the next 3 years, which will be just about the right time for my next ride. Anything before that would be too soon to work the kinks out. That's what our European friends / guinea pigs are for!
        • 7 Years Ago
        I just want a Subaru diesel engine to put in my VW T25. And as one of your European 'friends' I'll be glad to -'iron out any problems' for you. Would you like your nose wiped as well?
        Wasn't it a shame about the American motor industry! You made such.... well big ... cars. Ho hum....
      • 8 Years Ago
      #3, your generalization is unfair. I've have a couple of legacys now over 200k, and subaru's 2.2L EJ22 is considered one of the most durable engines ever engineered. The 2.5L have had head gasket problems, which have since been resolved.

      The problem that you're noticing is not with the engine, but with the owners. People who purchased Imprezza turbos beat the living snot out of their cars; i've yet to meet an owner who didn't drive one like a maniac.

      The second hand market for those is like a killing field.
      • 7 Years Ago
      Sadly the text is in Dutch but they do have a splendid video of the working bits in this engine! http://www.autokompas.nl/archief/2007/05/Subaru-onthult-eerste-oliegestookte-boxermotor.html
      • 8 Years Ago
      The boxing 4 has a second order moment imbalance, inherent to its configuration. (lookind down at the engine)
      The large axial offset only exacerbates that imbalance.
      Subaru's boxing engines have about a two inch axial offset, in order to fit the 5 bearing crankshaft and counterweights.(good for strength & boost, bad for balance)
      The M5 axial offset is only 17mm.

      and no constant pulsation exhaust manifold, to compensate for the L L R R firing [blub blub blub] of a boxing4.
      • 8 Years Ago
      My current 96 outback has 265,000 miles on it and I have passed it on to a daughter and I have been looking for a diesel replacement. I would like nothing better than having a Outback diesel, but if they can't deliver to the USA then the 2008 Volkswagen Jetta TDI will be my next purchase.
      • 8 Years Ago
      I am writing from Europe (Hungary). As far as I see here everybody talks about technical blu-blus... You have to know other reasons why Subaru needs a diesel engine. In Europe more than 70% of new cars sold are diesel powered in the (European) premium compack (like Impreza) and upper middle class (Legacy) categories. Anyway Subaru is very expensive here, plus they have no diesel = no sales. Simple. One liter of fuel here cost 1.20 $. An average not turbo charged Legacy with a two litres engine eats 11-12 litres for 100 Km. Right now I drive a Ford Mondeo Station Wagon which is bigger than a Legacy. The Ford has a two litres turbo diesel. The average consumption of the car is below 8 litres, with 131 Hp 310 Nm. Subarus cheapest list price for a Legacy SW is 36600 $ (two litres, 165 Hp 187 Nm). The Ford's cheapest list price with the diesel engine is 31000 $. Any more questions?
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