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]
BREAKING: GM and Chrysler talking about merger
Spy Shots: Nissan 370Z again, with interior shots
2010 Mazda3 unveiled ahead of LA Auto Show
Spy Shots: Nissan 370Z caught undisguised
GM on Corvette ZR1 cancellation rumor: "Not true."
Knight Rider: The Liveblog -- Season 1, Episode 3
In the Autoblog Garage: 2009 Mazda RX-8 R3, return of the "hummer"
In the Autoblog Garage: 2008 Chevy Corvette Z06
Autoline on Autoblog with John McElroy
Paris 2008: Le Day 1 Wrapup
Reader Comments (Page 1 of 3)
Tal D @ Sep 30th 2006 1:03PM
It's about time we see more diesels for our automobiles; if we see this one. In my my unscientific opinion Subaru FWD is superior to others FWD I've owned..esp in snow.The engine's low center of gravity makes the difference.If they build this one as other good diesels are built with the endurance, longivity. and less fuel consumption but with the power and torque associated with diesels, this could be a very desirable means of transportation. Hopefully we will see it here and I thank Subaru in advance.
ruggels @ Sep 30th 2006 1:08PM
i wasn't aware subaru still sold cars which were FWD in america?
Jim in Tampa @ Sep 30th 2006 1:09PM
I've driven a bunch of boxer engine cars including Subarus and I've never found them to be that smooth running.
james @ Sep 30th 2006 1:59PM
I had been looking for a used Subaru Impreza or Outback 2.5 non-turbocharged years 2003 or newer. Every single one I test drove had problems with the engine. They never ran smooth or started easily and struggled to last this long. There is a piston slap problem with this engine that still hasn't been fixed. I can tell you right now Subarus are not made to last.
MikeW @ Sep 30th 2006 2:22PM
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.
AK @ Sep 30th 2006 2:37PM
#3, tell that to my Legacy which is pushed 194k without major problems. Now at 200K it starts right up. That's definitely a crap job they pulled there when putting it together.
Boxer engines feel different from your normal inlines so that may be why you felt that it didn't "run smooth." In any case I hope Subaru brings this engine over to the U.S. in their Legacy models. It would be great to have Subaru quality with superb fuel economy.
AndyH @ Sep 30th 2006 2:44PM
"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.
chuck goolsbee @ Sep 30th 2006 4:02PM
I've owned two "boxer" engined cars, a 1973 VW 1303 (aka "Super Beetle") and a 1989 VW Vanagon (aka "Waßerboxer"), I would have a hard time keeping a straight face while saying they were "smooth" or "rotationally balanced". That said, they were very sturdy and provided fine propulsion for their day.
If you are looking for a smooth engine, the inline six is the choice to make. Of course there always in the legendary I-12 (http://www.brit.ca/%7Etboicey/comics/inline12.html) but it is only ... um... legendary.
I've never seen nor heard of a horizontally opposed Diesel engine, but don't doubt that they have existed at one time or another. The American market is DESPERATE for alternative fuel options, and Diesel should be at the head of that pack. I run my VW TDI on vegetable oil and when I tell people that they are shocked. The idea of running a car for under a buck a gallon is worth the effort I put into it.
Big Oil can kiss my @$$ and keep eating those french fries folks!
--chuck
Steve2 @ Sep 30th 2006 5:29PM
By passenger side for the turbo, do you mean port side or starboard side? Because the passenger side on a domestic Japanese car is the driver's side on a US version.
Lowering the CG for a Diesel will do a lot toward mitigating the increased weight.
sam @ Sep 30th 2006 5:32PM
#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.
risingsun @ Sep 30th 2006 5:37PM
Subaru did make a small number of 90s Impreza 2.2s that were indeed just FWD. VERY rare.
And Subaru's boxer engines are TOUGH. I have two coworkers with original generation Outbacks with 250K+ miles, getting the same mileage today that they did brand new.
A 2007 Outback 2.5i basic wagon is a LOT of car for $21995. The interior is head and shoulders above almost anything for that kind of money. Versitile, capable, good mileage, and refined. The cabin is quiet, the materials are top notch. Panel fit is great, and the small details in the cabin are well thought out.
Clarence @ Sep 30th 2006 5:52PM
Subaru is going out on a limb on this one. If it does not run smoothly and reliably, this will harm the brand, perhaps, irreparably. They better get it right.
Kumar @ Sep 30th 2006 7:57PM
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!
Ian @ Sep 29th 2007 4:25PM
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....
Joshua @ Sep 30th 2006 8:20PM
First off flat fours are NOT space efficient, an inline 4 of the same displacement occupies less space. The slightly lower c of g that you get with flat 4s could very easily be replicated with an inline 4 just by laying it on it's side. Something that would be very easy to do in a transversly mounted engine. The reason manufacturers don't is because it makes very little difference and introduces other packaging concerns... So what's the real reason that Subaru and Porsche use flat engines? Because if your commited to using a transversly mounted engine that must be on the wrong side of the driven axle, its the best way to cram as much of that engine as close as possible to that axle. This is important for Subaru otherwise they would be even more nose heavy than they are already, and it's important for Porsches (911s) otherwise they would be even more tail heavy than they are already. And that's it, that's the reason, please stop with the compactedness / good c of g garbage, thank you... Deep breath.
The important (and unspecified) issue about that diesel is wether they manage to make it out of aluminum or if they have to resort to a cast iron crank case. Because Subaru engines are entirely before the front axle an iron engine would make the car horribly nose heavy
Joshua @ Sep 30th 2006 8:48PM
Oops, in the post above I meant to say that Subaru and Porsche engines are of course longitudinally mounted, not transverly. Wish there was an edit function here...
Bob Zeliff @ Sep 30th 2006 8:49PM
I'm very happy to hear that Subaru is working on a Diesel. If they make it as reliable as their H4 engines and it get 29-20% better fuel economy, we'll get one.
PS our family has had 8 subarus and something over 500 thousand miles with no major problems, so I have high expectations for the diesel.
bob
AK @ Sep 30th 2006 10:07PM
#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
RallyWagon @ Sep 30th 2006 10:40PM
Oh and this nose heavy talk by #14 is just silly the motor wieghs barely 200lbs and sits with 2/3 of that weight behind the front axle. anyone who has even bothered to open the hood on a subaru can see that.
RallyWagon @ Sep 30th 2006 10:43PM
#4 and #5 could not be any more off base. First my '96 Impreza has 219k on it and still runs pretty strong even after a lot of abuse. My inlaws is well in excess of 150k and runs great. my brother '00 RS2.5 runs very well even after adding headers, exhaust and intake. His '95 managed a three month cross country trip with absolutely no issues. My friends '97 ran great before the 2.5L swap with 170K on it and runs great after the 143K prevoiusly turboed, not rebuilt 2.5L was put in to it. The motor in the vehicles you are test driving have had little to no change since '00 so I vote for bad owners.
The idea that the Subaru boxer is poorly balanced is nonsense. Its one of the fewer motors made without a harmonic balancer bolted the the front of the crankshaft. The design is inherently balanced.
The reason both Porsche and Subaru use the boxer motor as has Ferrari is that it is to place the crankshaft in direct line with the driveline while maintaining and low hood profile and CG for improved handling. The concept has been proven very successful in public and racing circles so why should they change?