There it is, Subaru’s all-new gen 3 engine, its first new boxer since 1989, and only the third since 1966 (full history here). As is obvious at first glance, Subaru has reverted to a DOHC head, after switching to a SOHC back in 2000. What’s not so apparent is that the internal architecture is very different: the boxer loses its oversquare (large bore/short stroke) configuration for… the opposite. Long strokes are in (again), favored for their compact combustion chambers and ideal torque curves. The new engine has a host of other goodies, and is expected to be 10% more efficient. But direct injection is not on the list. Nor is piston slap, hopefully.From Subaru’s Press release:
The New-generation Subaru Boxer engine
・ The bore and stroke, the basic structure of this engine, have been reviewed to achieve a compact combustion chamber as well as a long stroke, which was difficult previously due to chassis mounting conditions in boxer gasoline engines. This allows high combustion efficiency, and generates a sufficient mid-low speed torque with improved fuel efficiency and practicality.
・ Improved fuel efficiency has been achieved through optimization of intake port configuration and the addition of partitions inside ports, the use of TGV (Tumble Generated Valve), and the use of an EGR (Exhaust Gas Recirculation) cooler.
・ AVCS (Active Valve Control System) is used on both intake and exhaust valves. For the intake side in particular, an intermediate lock system allows valve timing to be advanced or delayed for precise control over intake and exhaust valve timing, allowing maximum engine performance in output, fuel efficiency, and exhaust emission.
・ The use of lightweight primary moving parts, such as pistons and connecting rods, and a highly efficient and compact oil pump provides an approximately 30% reduction in friction loss and improves fuel efficiency and revolution response.
・ Cooling has been optimized by using separate engine cooling circuitry for the block and the head, resulting in improvements in fuel efficiency and output characteristics.
The 2011 Forester will be the first recipient of the new motor, which will then spread across the line. Subaru has also announced its intentions for a hybrid version.
I wonder if they did anything about the oil consumption.
That is funny
Or the oil leaks….
My WRX 02 doesn’t take any oil! It have 201000km on it and no problem! I also had a 95 Legacy with 260000km and no oil consumption at all!
And if your car take some oil, try a different one! Go full synthetique with some Motul ou Gulf! :)
Subaru is doing it wrong; The MPG of their cars suck.
The first reason being because I think their AWD system is inefficient, and doesn’t get FWD like efficiency when you are on a plain dry pavement road. The AWD system should default to FWD and the computer should decide when to modify where the torque goes.
Also, and this relates to all cars in the USA, not just Subaru;
1. Direct Injection into the cylinder instead of multiport fuel injection, 5-10% increase in efficiency there.
2. Get rid of transmissions with torque converters (traditional automatics) and put in CVTs, dual dry clutch automatics and traditional manual transmissions. Not suprising that you can get 10% that way too.
3. Gas engines in cars in the USA are known as OTTO cycle engines. They should be modified to behave like an Atkinson cycle (also called Miller cycle), by leaving the intake valve open during part of the compression stroke to lower compression losses. This would only be applicable during certain RPM ranges and not 100% load. This could give you 5% increase in efficiency easily.
4. Cheap mild hybrid; Add a supercapacitor and have the alternator run at full load when the driver wants to brake and act as a motor when you want to accelerate. All that’s physically added to the car is an alternator that can also be a motor, a super capacitor if needed (Or just the stock lead acid battery) and computer software. Porsche and Mazda are doing that to their regular gas cars now for 2013.
5. Start/stop technology. The car should stop the engine when you are stopped and start when the computer senses that the brake pedal is releasing at full speed or when released fully if released slowly. 5% better city probably.
The only thing Subaru is doing is CVT, and Direct Injection (but only on their 2013 BRZ, all others are old fuel injection). They haven’t done anything else and their efficiency suffers because of this.
“I think their AWD system is inefficient, and doesn’t get FWD like efficiency”
That’s because it’s driving two more wheels… use your head.
“The AWD system should default to FWD”
Why the hell would you want it to default to FWD? If anything, put the power to the rear!
1. DI would be nice.
2. Yes, the 4EAT f***ing sucks.
4. They’ve already planned it.
5. Also planned.
The new WRX line hasn’t been announced, nor has their choice of engines. Wait to see what they have in store before jumping to conclusions.
Our 2000 Forester (130k) sounds like an old diesel on cold mornings, but it never burns a drop of oil; even after 10k miles, the stick is till right on the Full line.
I read the full press release and it somewhere it said something to the effect of “designed with future technology in mind” – I’m sure its set up so it can get DI in the future.
“which was difficult previously due to chassis mounting conditions in boxer gasoline engines”
Which means “while our cars used to be too narrow to have a long stroke (think inner fender clearance), now they’ve gotten fat and wide and its not a problem.” So bigger Subarus are apparently here to stay. I tend to think the EJ20 and EJ25 will live on in the WRX and STi though, that undersquare low revving just doesn’t work for the high performance tuner market.
Also Paul, my 2005 Legacy GT was DOHC. They’ve had both DOHC and SOHC versions of the current engines I believe, the turbos being DOHC.
BTW, I don’t know if its a WordPress thing, but I hate the new commenting posting system. It takes me to another page to edit, and I never can get line spaces right.
+10% MPG puts it just par with current competition. Hopefully they have some new transmissions too. I would really like a 6 spd manual Forester with 30 MPG right about now.
They’ve had a six speed stick in the STI’s for years and it will probably bolt right into a manual Forester if anyone really wanted one. What they really need to compete in the market is a 6-speed auto.
Subaru already showed off a direct-injected boxer engine at the last Tokyo Motor Show. Also, the “D-4S” engine that they will be sharing in the Toyota FT86 is also a direct-injected boxer engine. So Subaru clearly plans on introducing direct-injection in their lineup.
The engine that Subaru is showed the specs to in the press release is the base 150ps engine, so there should be no direct-injection in it. I’m guessing that Subaru will have direct-injected and normal multiport injected versions of this engine with directed-injection saved for vehicles which they have more margin to cover the cost-premium of the direct-injection system (since DI systems require both DI & MPI injection systems).
Is this a nail in the coffin of parts interchange among nearly two decades of Subarus?
In general, a longer stroke engine allows for a more efficient power stroke, or expansion phase. I suspect we will see more and more engine redesigns go back towards longer stroke designs to capture this greater fuel efficiency potential.
Short stroke designs are all about enabling high RPM performance, but they trade off thermodynamic efficiency in doing so.
Yeah, longer stroke is going to be the way to go with the newer emphasis on economy over speed.
Not exactly new engine design- Volvo’s modular “white block” (introduced in model year 1991) was an undersquare design for improved economy and emissions over the old, oversquare “red blocks”.
I agree- Subaru assessed the next couple decades of the automobile and made a decision to hedge on fuel economy.
So I was thinking really hard about buying a 2011 WRX 5 door. What say you all about waiting till this motor gets in the Imprezas. I think the old (present one) works just fine for the money. I had a 2005 Outback XT (2.5 SOHC turbo) that didn’t have piston slap or burn oil. I had a 5.4l Ford at the time as well that had the slap until warmed up but did not burn oil and that motor has a long stroke. The one thing about these is they have a chain driving the cams instead of the belts. Good thing.
What? No DI? This is terrible. Subarus turbo engines have tons of lag and get crappy mileage. They REALLY need direct injection. The small bore may complicate adding DI with a new head later, too.
I don’t get the advantage of a smaller chamber and longer stroke. It would shorten the nose of their cars slightly though.
“I don’t get the advantage of a smaller chamber and longer stroke. “
Better thermodynamic efficiency. In other words, more of the fuel’s energy can be turned into power with an under-square design than can with an over-square design (generally speaking).
According to the 2011 Forester spec, the new engine produces exactly the same power and torque and only improves mileage by 1 MPG. You would have thought that all that R&D would have produced a more dramatic improvement. Maybe they should have spent that money on a decent 6 speed auto box instead.
It’s the same size engine, pushing the same size load through the same old trans. That the mpgs went up at all is proof of a better engine.
When Subie finally announces a 6-speed DCT, at that point, their mileage will go up by a goodly chunk, especially in the real world.
I really don’t like the raspy, lumpy boxer engine sound; I wonder if they fixed that. It’s enough to make me not buy one.
But kudos to Subaru for making meaningful continuous improvements and really moving forward with sales.
However, their prices are moving upmarket, too, in step with demand. The cheapest Sub today is over $18k and only gets 20/27 mpg – not a competitive combination except for the AWD which most people don’t need unless they’re drinking the Subaru Kool-Aid.
Kids, today.
Engines should make an interesting noise, and if I’m not going to hear a V-8 burbule, I’ll be happy enough to hear a boxer.
If you live in the Rockies and have to deal with steep streets or driveways, then AWD buys peace of mind. I’d still recommend a set of proper winter tires, but many folks still get through the winter on all-season tires.
Lexus LF-A makes an interesting noise.
@OldandSlow: Here in the Pittsburgh area of western Pennsylvania, we have many steep driveways and streets. Subaru certainly builds an excellent AWD system, but they’ve built market share by convincing people that they need AWD. Around here, that might be 2% of the year, and most people shouldn’t even be out in those conditions.
Peace of mind, yes, but I’d rather put my “AWD premium” into winter tires for a more economical – and simpler – car.
On the other hand, I’d take the Subaru system over Audi any day, if only because it will be more reliable.
“I really don’t like the raspy, lumpy boxer engine sound; I wonder if they fixed that. It’s enough to make me not buy one.”
That’s due to the routing of the exhaust; there are aftermarket bits changing the exhaust path that will make it sound like any other inline 4. Though personally I think it’s a nice bit of uniqueness, just like the starter motors on Hondas.
Congrats! You are the only one who understands the concept of low-end torque with this redesign!
It will probably sould like a bag of marbles in a blender at high RPM but maybe the boxer design will help.
Heheheh… let’s hope not- bad knock also sounds like a bag of marbles in a blender, followed by the sound of a lot of money being exchanged.
For your future reference this is the actual sound of marbles in a blender
Cooling has been optimized by using separate engine cooling circuitry for the block and the head, resulting in improvements in fuel efficiency and output characteristics because we never did figure out how to make a decent head gasket.
My question is whether they’ve gone back to timing chains.
The new engine is chain-driven.
Are there any boxers which don’t eventually leak?
Anybody got an old 911 which doesn’t leak?
Way back in ancient times, the the boxer engine in my Beetle neither leaked nor burned any oil.
Except, that is, when an errant rock would bend a pushrod tube and break the its seal with the block and/or the cylinder head. (No, I certainly don’t miss doing the pushrod tube replacements.)
So confused….
To DI or Not to DI!
I have 20K on my second, yes…second, MKS.
No problems.
DI AND twin turbo are what Ford is beating its chest about.
Now I begin seeing these reports by B&B about build up due to DI.
Is it or is it not a problem?
If it is, is it a problem with some DI designs or something inherent with the design?
I sort of thought this was beginning to be the standard on all future engines.
Last thought…I like the different sounds different types of engines make.
Sort of a personality thing.
I even like the sounds of diesel engines.
Kind of like the sound of victory, or power.
Not the sound of straining or gasping for breath, but just like the sound of Indy cars at full blast. Like perfectly tuned hornet buzzing.
As a matter of fact, some over the top tuning of mufflers often bugs me. It’s like a false macho (is that redundant?) or something.
Here in the Ozarks having over blasting mufflers on your truck or mustang is something you have to have along with your tribal tatoo ring on your arm!
What’s even worse are those fart pipes on tiny little Honda cars that tale 15 seconds to get going off a red light.
The silly kid keeps changing gears while the rest of us following keep having to apply our breaks or we’ll rear end him.
My Outback sounded like an anemic VW, got crappy gas mileage and lit up the check engine light whenever it felt like it. I’d never get another Subaru. Hope this new engine makes it easier to change spark plugs — last one was a bitch.
Twotone
The use of lightweight primary moving parts, such as … connecting rods
Anyone know the con rod material?
Nobendium
What is actually the advantage for them to stick with boxer? From what i grasp he disadvantages are:
– more parts (= more friction, more cost, more to break)
– hard to access (just compare spark plug change)
– wider
– the mileage is not better (and i already give credit for AWD)
– maintenance is a pain (my wife and mother in law both used to have Subaru and the maintenance bills are horrendous plus repair .. head gasket?? they still have timing belts??)
So, without bashing Subaru, why do they actually use boxers? Only Porsche i know of that use Boxers (and they are expensive and not really known for reliability either). It can’t just be the sound, it also can’t just be using the older design if they re-developed this one. And potentially less vibration can’t be the main reason to outweigh all the disadvantages. Not that majority is always right, but there may be a reason while everyone uses I-4.
I’m not sure if they addressed any of the old problems (timing belt??)
I’ve never owned a Subaru and I don’t know for sure, but I can think of a few reasons why Subaru might be sticking with a boxer engine: Packaging, and probably to a lesser degree, weight distribution and center of gravity.
If I’m not mistaken, Subaru uses a longitudinally-mounted engine for its vehicles, all of which are available with AWD (which is standard in the U.S.). This allows equal-length halfshafts in front and it’s likely easier (and perhaps also more efficient) to route the power to the rear than it is with a transverse-mounted engine. A four-cylinder boxer is shorter than an inline design, so the transaxle can be lined up with the engine without the need for an excessively long nose.
Since the engine is shorter, it (and its mass) can be placed further rearward, which shifts more weight toward the rear axle.
Finally, a boxer is not as tall as an inline engine, so the vehicle’s center of gravity is lower.
But beyond the practical reasons, the boxer engine is simply one of those things that make a Subaru unique, and why the brand has so many devotees.
Subaru uses boxers because the design is fundamentally sound from an engineering standpoint. Inherently balanced engines are simply better compared to a V-6 or I-4, and the parts count and friction are certainly superior – no balancers or counterweights for starters. Reduced vibration means it’s not constantly tearing itself, and the rest of the car, apart.
Access to plugs isn’t a big deal, considering how long they last, and how few people don’t have the dealer change them.
Wider was an issue, when cars were narrower. Not anymore.
Maintenance isn’t cheap at any dealer. Subarus will run longer, badly than many cars will run.
Subaru SAWD wants short, low engine block in front of the front axle, with the trans & AWD behind the front axle – it gives far better front/rear weight distribution compared to a FWD-based AWD system (e.g. Quattro), safer than RWD-AWD (e.g. Porsche), and far less mechanical confusion (e.g. anything using trucklike 4WD transfer case). It’s a very sensible layout, in the same sense that BMW does a RWD chassis.
Subaru’s engine choice is predicated on AWD. It’s an excellent choice for their application.
The majority use I-4 and V-6 engines because they are compact enough to fit in a FF transverse layout between the wheels, not because they are “better”. These I-4 and (especially) V-6 engines are inherently deeply compromised in order to fit a packaging requirement. They weigh more, and have more inherent frictional and rotational losses. The nose-heavy layout and pulling with the steering wheels gives inherently poor dynamic response and low active safety.
If you ever get a chance to drive a XT6 or SVX sport coupe, you’ll see very clearly why the F-6 engine is a good choice for Subaru.
Twice the camshafts, pulleys, cam boxes, “active valve control system” parts, etc. adds up to less parts than a single balance shaft on an I-4? I’m not disagreeing with you, but it seems hard to believe.
I think Subaru keeps using the boxer layout just to be different, not because it is actually a better design. Likewise, Subaru seems to remain committed to putting AWD in every vehicle, and for many users that is also silly.
A modern inline four does not have a higher total parts count than a Subie 4. The extra head, extra camshafts and extra camshaft drive chain/belt issues of a flat-f more than compensate for the parts count of a balance shaft system.
Compared with a V-6? The F-6 is a slam dunk.
Compared with an I-4? The question is whether you’re buying an appliance or not. For toaster duty, sure, go with the I-4. For a better engine, I’d get the F-4.
Subaru would have to essentially re-design all of their vehicles to lose the boxer design.
Subaru only offers AWD. If you are going to power the rear wheels from a front engined vehicle – then a north/south layout makes more sense, than a transverse engine. In Subaru’s case, the flat four, boxer engine reduces the front drive train overhang by two cylinders – plus it lowers the center of mass, provided that the engine cradle allows the engine to be mounted at or near the level of the front and rear axles.
There are downsides. One – there is less power train loss with a transverse front engine, front wheel drive only, toaster-duty design. Two, as mentioned, the boxer designs require two separate valve trains versus an inline four. Then to meet of emissions, a more complicated exhaust and exhaust gas recirculation plumbing is required. Plus, it is a tight fit between the heads and body assembly – which may come into play servicing a leaky valve cover gasket or as you mentioned changing the spark plugs.
Subaru got rid of the timing belt with this new engine. Hopefully, the cylinder head gaskets are more robust than the old 2.5L as well.
Also to HerrKaLeun – for a true AWD vehicle with somewhat high ground clearance as is the case with either the Forester or Outback – the Subie offers a decent compromise between having AWD performance in the snow with fuel economy – which is on par with its competitors in the segment.
Any news on a diesel making it to North America?
There’s Euro diesel version but I have no idea just how series of an effort it is on the part of Subaru.
I see some rather unsubstantiated claims about long stroke engines having better thermodynamic efficiency than short stroke ones. Can anyone cite some proper engineering references as to why this should be so? Because I’ve never run into any myself.
In fact, the opposite claims are usually made. A larger bore allows bigger valves and better breathing, and the total distance for a flame front to travel from a central plug to the extremity of the cylinder is less, because the capacity of the cylinder increases as the square of the bore and only linearly with the stroke.
Then. everyone goes on about long stroke engines having better torque. Hmm, like Hondas, you mean, which have a hard time removing the skins from rice puddings at low revs in my experience. Remember that a bigger piston puts more force onto the longer stroke, and there isn’t much overall difference, as witness the old and new engines here.
The only reason I can think of for the change is to make the pistons much lighter, and to make it easier to have a compact combustion chamber. But each ring will have to move farther and faster in the bore, and each rod big end will encounter more sliding friction on the crank.
I’d have to say it’s a bit of a wash, but allows the new engine to be more like the diesel casting.
I’m open to anyone’s referenced arguments as to the merits of a long stroke. But lowered volumetric efficiency with the smaller valves does not equate to higher efficiency, and the thermodynamic efficiency argument I’ve only read as anecdotes rather than real engineering findings.