The name Subaru carries a lot of weight. For many drivers, a Subaru might represent world-beating all-wheel-drive, safety, and quirky boxer engines. But one thing Subaru has never been known for is diesel power. For a period in the late 2000s and the 2010s, Subaru tried to change that with the world’s first diesel boxer production engine, the EE20. Unfortunately, it took Subaru years to perfect the engine and by the time it was about right, diesel no longer made any sense.
Diesel passenger cars used to be a huge deal all around the world. Automakers made a heavy diesel car push in the 1970s as a response to multiple oil crises and poor economic conditions, but many of those automakers went right back to gasoline once the fuel got cheap again.
But the promise of the diesel passenger car never really disappeared. Back in the 1980s and early 1990s, diesel power in a car was an interesting niche. Tiny diesel engines promised substantially better fuel economy than a gasoline engine and at the time, it was believed that diesel could be turned into a greener fuel than gasoline. America turned away from diesel cars after GM’s Oldsmobile diesel blunder in the 1970s and a sharp drop in the prices of gasoline.
Over in Europe, the situation was different. In 1990, just 10 percent of the new vehicles that were sold in Europe were diesels. By 2011, a whopping 60 percent of all of the cars sold in Europe had diesel engines. If you broke the land down by country, some places had a full-on love affair with diesel, like France, where some 80 percent of new vehicles sold there were diesel.
What gives? As the U.S. Department of Energy writes, diesel was cheaper than gasoline in most parts of Europe and sometimes the price gulf wasn’t even close. During points of the 2000s, gasoline was a whole 95 cents more expensive per gallon than diesel. Several countries in Europe supported the idea of diesel as a greener fuel and there were advances in biodiesel to support it. As the Guardian reports, European countries also sweetened the deal for both automakers and consumers alike with subsidies for going diesel instead of gasoline.
The result was that, for a while, diesel was the default option in Europe. Eventually, diesel car fever even infected America. Automakers saw how much success Volkswagen had with its TDIs and wanted a piece of the market. While diesels were never the primary engine of American cars, about a quarter of Volkswagen of America’s sales were for diesels, so for many automakers it was something worth pursuing.
One of those automakers was Subaru. In 2004, Fuji Heavy Industries (FHI) took note of the rise of diesel cars in Europe and China, two markets it wanted to get more sales in. That year, reports announced the start of a Subaru diesel exploration program that had the goal of putting 2.0-liter diesel-powered Forester, Impreza, and Legacy cars in Europe. Later, Subaru announced that America would get this engine, too.
Subaru did hit its mark, launching what it called the world’s first-ever diesel boxer engine in 2008. It seemed like a promising engine, too.
Subaru Was A Late-Bloomer To Diesel
Something I’ve noticed is that none of Subaru’s press releases state that the EE20 diesel is Subaru’s first-ever diesel. Instead, the FHI company kept boasting about how it was the first diesel boxer. Technically, FHI was incorrect in its assertions of inventing the diesel boxer. Volkswagen had a prototype diesel boxer engine in the 1950s.
[Editor’s Note: Sorry, I just need to jump in here for a moment, because I find the 1951 Volkswagen Diesel Beetle story pretty amazing. For a number of reasons in the early 1950s (Korean war making gas expensive, diesel dirt cheap) VW wanted to at least experiment with a diesel engine for the Beetle, so they contracted Porsche to build one, which Porsche called Project 508.
The engine Porsche came up with used a three-piece crankcase from their 356 and displaced 1.3-liters; it was, as you may guess, slow as hell, requiring a full minute to get to 60 mph. It made, at best 25 hp, which was pretty much on par with what a gasoline Beetle of the era made, but somehow the diesel was slower. You can see in the picture up there the fuel injection system to the left (making this also the first FI Beetle) and the lack of a distributor.
The story I like best about the diesel Beetle is that the one prototype was stolen from a parking lot and driven all the way to Switzerland, where it was abandoned, the thief likely thinking that a louder, smokier, slower Beetle just wasn’t worth it.
Anyway, back to Subarus. – JT]
However, FHI would be technically correct to say it’s the first production diesel boxer car engine.
That’s because Subaru has an interesting history with diesel. Its parent, Fuji Heavy Industries, Ltd. (now known as the Subaru Corporation), had its hands in a little bit of everything from the manufacture of railway rolling stock to buses and aircraft. Yet, its diesel portfolio has been pretty tiny.
Back in 2001, FHI inked a deal with German firm Farymann Diesel GmbH to resell the latter’s industrial diesel engine as the Robin DX. This engine was commonly used in generators and would later be renamed the Robin-Subaru diesel and eventually just the Subaru Diesel. To be clear here, this engine wasn’t sold by Subaru the automaker, but FHI subsidiary Subaru Industrial Power Products.
What about cars? Well, that gets pretty fun, too.
Get ready to get confused because in the early 1990s Subaru sold more than one version of the Leone. The Subaru Leone Van, which was equipped with a 1.7-liter CD17 four-cylinder diesel, was actually just a rebadged Nissan AD wagon. That engine? Yep, it was also from Nissan. This was sold alongside other Leones that were real Subarus.
Subaru did something similar in 2003. That year, European buyers were able to get their hands on what was known as the Subaru G3X Justy. Here’s a clipping from its release:
The G3X Justy* was a compact car introduced to the European market as an entry-level model for the crossover vehicle category. Drivers enjoyed the sporty driving feel that Subaru had become known for, and the entire line-up was equipped with DOHC engines and a dynamic design. The G3X Justy was available in an AWD model powered by either a 1.3-litre or 1.5-litre DOHC engine with a variable valve timing (VVT) system, as well as a front-wheel drive model with a 1.3-litre diesel turbo engine. It offered high-performance driving both on rough and on roads, with a minimum ground clearance of 170 mm.
Ah, what’s going on with that asterisk? From Subaru:
* Produced by Magyar Suzuki (Hungary).
Yep, Subaru’s European diesel hatch was just a rebadged Suzuki Ignis. In other words, if you happen to find any Subaru equipped with a diesel engine that’s not the EE20 of 2008 and later, the engine did not come from Subaru.
FHI must have had that on its mind in the early 2000s. In 2000, the Japan Times reported that Fuji Heavy Industries made its first-ever diesel car engine. This engine, which FHI also said was the world’s first horizontally opposed diesel engine, appears to be the ancestor of the Subaru EE20. Back then, Subaru was considering putting it into production cars, from the Japan Times:
Mamoru Morinaga said the 2000cc, four-cylinder engine, the first diesel engine developed by the company, will be installed in a remodeled version of the Forester sport utility vehicle, which has recorded brisk sales in Europe.
“We considered purchasing it (a diesel engine) from other companies but have developed it on our own while sticking to our horizontally opposed engine technology,” he said. Morinaga said the company plans to install the engine in a minivan currently being developed jointly with General Motors Corp. of the United States.
The company plans to manufacture up to 100,000 of the engines annually in Japan or Europe, he said.
Fuji Heavy Industries will seek cooperation from Japan’s Isuzu Motors Ltd. and Italy’s Fiat SpA, two of GM’s group companies, to mass produce the engine and reduce its emissions, he said.
It’s unclear what happened to this first engine, but reporting from 2004 suggests that development on the EE20 began that year, not in 2000. What was clear is that the engineers in 2004 and 2005 weren’t going into this blindly.
The Subaru EE20 Diesel
In February 2008, Japanese tech news outlet TechOut reported that Subaru did it. The automaker’s engineers spent the three years prior putting together what was supposed to be an engine of firsts. It was Subaru’s first in-house production diesel and the first production diesel boxer anyone had ever seen in history.
TechOut reported that one of the immediate advantages of the EE20 boxer diesel was its compact size and its lower weight. According to the publication, the EE20 was 13.9 inches long, or 2.4 inches shorter than a Subaru EJ20 gasoline engine. Subaru wasn’t willing to release weight specifications, but claimed that the EE20 was about 22 pounds lighter than a common four-cylinder diesel engine from Europe.
In other words, it sounds like Subaru’s engineers spent their time trying to add Subaru character to their unique diesel boxer. The EE20 even had a bore pitch of 98.4mm, the same found in the EZ30 H6 used in the Legacy and the Outback. TechOut also noted that the EE20 was built in the same Ooizumi assembly plant responsible for the EZ30 boxer.
Perhaps the coolest part about the TechOut report was a technological deep dive on the engine:
The engine block is of a semi-closed deck design as in the case of the EJ20 and was rigidized by journals cast with iron metal. As for the piston, the company used “a high-strength material” that withstands high temperatures and pressures and shorten the compression height (the length between the central axis of the piston pin and the upper surface of the piston) to 43.0mm to downsize the block.
The company adopted a fracture splitting connecting rod, which will be used in the 3.6-liter six-cylinder engine mounted in “Tribeca,” an SUV sold only in North America, to save the need to process the matching surface and to downsize the engine. The cylinder head was also rigidized so that it can withstand high temperatures of the diesel engine. Also, a roller rocker arm was used to reduce frictional loss. The camshaft is driven by a chain and gear with a speed-reducing gear.
The injector is a solenoid type developed by Denso Corp. Its basic structure is the same as existing products, but it is 40 to 50mm shorter than other companies’ injectors for inline engines. The rail pressure of Denso’s common-rail system is 180MPa, the same as that of the products developed for manufactures in Europe.
It was noted that Subaru’s launch vehicles for this new engine in 2008 were the Legacy and Outback. A huge deal to Subaru was to deliver a seamless driving experience. In the 2000s, diesel had finally moved away from its reputation for being loud, clattery, and rough. Instead, European diesels like Volkswagen’s so called “Clean Diesel” TDIs felt closer to their gasoline counterparts.
Subaru recognized this and in an effort to smooth out the EE20, it added a diesel-specific dual mass flywheel and damper. At launch, Subaru’s diesels had five-speed manuals, but not automatics. TechOut continues:
The vibration noise of the EE20 is small. Horizontally opposed diesel engines do not need a balancer shaft because they generate less secondary vibration compared with inline and V-type engines. Fuji Heavy Industries minimized the vibration inherent in diesel engines by shortening the total length of the engine and rigidizing its parts.
The EE20 is mounted with a variable nozzle turbocharger developed by IHI Corp. Its maximum engine speed is 190,000rpm. The turbo lag, which is a problem with turbo gasoline engines, was reduced by placing the turbo in the lower right of the engine to shorten the distance to the exhaust manifold.
Furthermore, an oxidation catalyst and DPF (diesel particulate filter) were placed right next to the turbocharger to make effective use of the heat energy of the exhaust air. And Fuji Heavy Industries lowered the combustion temperature by using a water-cooled EGR (exhaust gas recirculation) cooling system to comply with Euro4 emission standards.
As Motor Trend writes, all of this engineering wasn’t a walk in the park. Subaru was married to its iconic boxer engines, so the struggle came to turn a boxer into a strong diesel engine without putting on too much bulk. What Subaru’s engineers did is impressive when you remember that not only did the engine not outgrow Subaru’s existing engine bays, but engineers actually managed to make the diesel smaller than a gasser. According to Motor Trend, the principal cause of the size reduction was the use of an asymmetrical connecting rod and crankshaft. This allowed the longer stroke required to hit a compression ratio of 16.3:1 without a physically larger engine.
The spec sheet was pretty good, too. At launch, the EE20 2.0-liter flat four boasted 148 HP and 258 lb-ft of torque. These were great numbers for 2008. That same year, Volkswagen launched its CBEA and CJAA TDIs, which made 140 HP and 235 pounds of twist. The Subaru delivered great vibes at the pump too with 50 mpg on the highway.
If you thought that an engine with these specs would have made for a great Volkswagen competitor, Subaru did, too. In 2008, the automaker announced that America was going to get EE20-equipped cars in 2010, which would have been right on time for diesel cars to hit their peak in America.
Other goodies noted by the Green Car Congress include liquid-based engine mounts for further smoothness, electric power steering for enhanced efficiency, uprated brakes, longer gear ratios, and an HVAC system designed to blow warm air sooner.
Motor Trend‘s review notes were pretty short:
The topline models we tested came with nav, leather, power driver’s seat, moonroof, and 17-inch wheels fitted with Bridgestone Potenzas. The only thing that really took getting used to was the pushbutton start, a feature not offered in the States. After a few tries at caressing the right side of the steering column and dash like a loved one’s shoulder and finding no button (it’s on the left), we were on our way. The engine is somewhat noisy at idle, but that disappears once you get up to speed. Subaru has done an excellent job of isolating engine noise from the cabin, and despite some wind noise, it’s still easy to chat with passengers without having to raise your voice. This turbodiesel is surprisingly smooth, with little turbo lag. It hums along at freeway speed at 2000 rpm and eats up mountain roads in third gear. The car’s weight is still biased toward the front, but the vehicle is well balanced, stable, and sticks to the road. The new engine adds about 75 pounds to the Legacy and Outback.
At launch in 2008, a diesel Subaru could be had for £19,995 ($38,800 in 2008 money) for the Legacy 2.0 TD R. Motor Trend figured that adding the EE20 diesel to an American market Subaru would have added about $2,000 to the price of a Legacy or Outback.
Why The EE20 Is Subaru’s First And Last Diesel
Back in 2004, Subaru had strong ambitions for its diesel program. It saw a future where Subaru diesels were popular options in its biggest markets of Europe and America and in the then-growing market in China. But things didn’t really work out that way. The EE20 never launched in America. Instead, Subaru expanded the EE20 into Australia in 2013. Cars with the EE20 also finally got the option of a CVT in 2013 as well.
Early EE20s also managed to gain a negative reputation in Europe. If you search the net for “EE20 crankshaft failure” you’ll be overloaded with floods of complaints. You don’t have to look very hard to find complaints of crankshaft failure, but here’s one person from the SubaruForester.org forum:
I had my crankshaft broken + engine block cracked on my 2009 Legacy Diesel (Euro4) @ 130.000 Km.
Toyota of Algeria, the dealership of Subaru here is denying everything and I’m gathering informations about this issue to sue them and force them to take their responsibilities.
And another unfortunate soul:
Hi mates,
Does anyone heard about this disaster of 2008 boxer diesel engine? It is a third one in Bulgaria at 85000km , breaks after normal driving around 100km/h! Warranty expired 2month ago! We are looking of e-mail of FHI in Japan to complain.
I have the exact same issue, my Impreza Diesel (EE20 Engine) 2010 Model has a broken Crankshaft. While driving at a very steady 65mph on the motorway in 6th Gear i got an engine shudder, nothing loud or scary and the engine just died/stalled. Got picked up by recovery and taken to local garage and engine stripped down and crankshaft completely snapped into 2 very clean pieces.
Dealing with Subaru just now but its like pulling teeth with them.
Subaru Impreza DRX Diesel 44,000 miles, well serviced.
That complaint contained an image of a crankshaft that was physically split in half. This issue became such a huge deal that in 2019, after the engine’s discontinuance, German car publication Auto Bild wrote a saga about why you should avoid the EE20, translated into English:
[P]roblems with clogged soot filters, increasing engine oil content, knocking noises caused by imprecise injectors and finally major engine damage, often due to the crankshaft breaking. But the crankshaft isn’t really to blame. Rather, it dies a slow death from the slightest vibrations caused by worn crankshaft bearings. And they only wear out because the aluminum engine block isn’t rigid enough. One warning sign is leaking engine oil. Simply replacing the shaft seal in question only provides temporary relief, as in reality it no longer holds back the oil because the crankshaft bearings are already damaged and the shaft is therefore running unevenly.
The Subaru people, known for their appreciation of their customers, are dismayed. And they are doing everything they can to put things right. Cars are being taken back, engines are being replaced and the boxer diesel is being further developed. There are therefore several versions of engine housings. And indeed: the problem cases are becoming less frequent. Things are getting better from 2010 and even more so with the introduction of the Euro 5 diesel in 2015, when a new engine block is again supposed to ensure peace of mind. But customers are put off. The ten years of diesel have cost Subaru huge amounts of money: for development and testing and for warranty cases and repairs. Turbochargers and high-pressure pumps rarely cause problems – unlike other brands – but the additional problem of defective or imprecisely working injection nozzles (here from supplier Denso) also affects Subaru.
Fatal: They cost 500 to 800 euros each. 32 percent of diesel XV owners among our readers are also affected by the engine problems. The engine was also installed in the Forester , Impreza , Legacy and Outback in an identical design.
Sadly, as Auto Bild notes above, the issues were hardly limited to crank failures. It also seemed Subaru hadn’t implemented a reliable emissions system, either. Auto Bild was one of the publications that was on top of these issues when they were happening while the engine was in production. In 2012, it reported:
Subaru has problems with the diesel boxer. Indications of engine damage come from Sweden, where 109 of the 12,000 diesel boxer engines delivered have already been replaced free of charge. A Swedish Subaru spokesman confirmed this to AUTO BILD for the Legacy and Outback models from the production period autumn 2007 to February 2009. According to Subaru , the damage usually occurs at mileages between 65,000 and 80,000.
Two causes were identified: silicone drops that got into the crankcase during the assembly process can affect the engine lubrication. In addition, crankshaft bearings were installed with too little play. According to Subaru , there are also isolated cases in Germany, but exact numbers are not known. If engine damage occurs, “each case is examined individually, taking into account the proven maintenance and vehicle history” with a view to goodwill, said a spokesperson in response to an inquiry from AUTO BILD.
Despite all of the bad news, Auto Bild is quick to note that there are lots of these engines out there with high mileage and no problems. European garages also know how to do some bulletproofing to these engines, too. Some owners also say that the later versions of the EE20 have most of the above kinks worked out. All of that is great!
However, it would seem all of this came a bit too late. In 2016, Subaru announced that it was ending all development on the EE20, citing stringent emissions standards for the decision. A year later, Subaru threw in the towel. By now, the popularity of diesel had plunged thanks to Volkswagen’s actions and the Dieselgate emissions scandal. The world began moving away from diesel cars and toward electrification. Subaru followed suit, deciding to end diesel production to free up capacity to begin an electrification program.
Amazingly, it’s possible to get one of these EE20s in America. When it was found out that Subaru wasn’t bringing the EE20 in America, tuner shops tried to fill in the gaps by importing European EE20s and converting U.S.-spec Subarus. These shops even put a handful of these boxers in VW Vanagons. But it’s noted that these conversions weren’t cheap and thus, not really realistic for someone just wanting a normal diesel Subaru. They’re more for the novelty of having a diesel boxer. Here’s one EE20 for sale in New Jersey for $1,500.
In the end, Subaru moved roughly 15,000 diesels a year globally, so it was never a huge market for the automaker. Subaru also just came pretty late to the diesel game. Most of its competition had been building diesels for decades and knew how to make them reliable. Had Subaru done this far sooner, perhaps this might have been a different story. Instead, it’s a footnote in Subaru history that you can find on its pages only through some deep digging.
Subaru’s boxer was a cool little mill, but apparently not particularly solid in its early years. So, it ended up being a short-lived triumph. The world’s first production diesel boxer was also its last.
Doesn’t that sound like the RTV issue on BRZs and GT/GR86s?
I had EA81&2 Subarus—and was just getting into the Mercedes 617–when they announced the diesel boxer. As I was doing the waste vegetable oil thing, and diesel was much cheaper then, I liked the idea. Then my sister’s 80k mile 2.5RS popped the head gasket during a gentle shift 2->3 despite meticulous maintenance, and I became a bit dubious.
I considered gettin the Outback as diesel for company car in the ’12. However it was not really that great engine. On paper it’s fine, however low end torque was not quite as flexible as other 2l I4 diesels and it stalled easily. Also the fuel economy was quite bit worse than competition. And it really was not that refined either. Add that to a bit low rent interior, I skipped.
We had a used 2013 Outback diesel, with the CVT. It was great until it wasn’t. After 3 months the DPF light came on, then again, then again, then again. Every 2 weeks it was back to the dealer. Turns out that the DPF couldn’t handle normal every day driving. It needed to be hot run daily. You couldn’t use it to go to the shops. It was that bad! Subaru NZ bought it back and heavily discounted a new 2016 2.5 (incidentally we still have it). The diesel was a nicer car to drive it had acres more torque, and it paired with the lineartronic CVT better than the petrol does.
Kinda surprised they didn’t use a 6cyl as a first since 6cyl is naturally balanced also “premium” in spec sheet. 50% more parts is i guess why.
Surprised at the crank issues as my old Subaru had minimal rev limiters. Like my 88 fuel cut at 8,000. Ej20 in STi hit 8,500 iirc on some trims.
The price of the fuel was really a bonus. The big draw of diesels once turbocharging and direct injection was figured out was that you got *performance* without a big fuel economy penalty. Not so much pin you back in the seat straight line performance, but effortless daily driving shove. In something like a Golf, you could get the same fuel economy out of a wheezy 1.4L gas engine and have to rev the nuts off the thing to get out of it’s own way (and it still wouldn’t, and you’d kill the economy doing it), or you could get a TDI and have smooth, quiet real world power at low revs with stunning economy.
It was great until emissions standards killed what made diesels great, and then gasoline direct-injection was figured out which very much narrowed the gap for less money. As an example here in the states, reality is that a VW 1.4T gas motor has basically identical performance and fuel economy to the 2.0L TDI for less upfront cost and WAY less if you have to fix it. And of course, here, unlike most of Europe, diesel is usually rather more expensive.
I’m not surprised that Subaru screwed the pooch with their diesels, that was the same era when many of their gas engines sucked too, no?
> you could get a TDI and have smooth, quiet real world power at low revs with stunning economy
It is undeniable that the VW TDI had good torque at low revs and really good fuel economy, but if somebody describes these engines (the 4 cylinders) as “smooth and quiet”, I wonder if you have ever driven one? I have made lots of miles in both the 1.9 and 2.0, and they were horribly loud, clattery and vibrated incredibly strong for a modern engine, unless you got up to highway speeds, where wind- and tire noise tended to make it seem quieter (it wasn’t, it just felt quieter). But I will admit that it was somewhat bearable at higher speeds.
I bought one new, an ’02 Golf GLS. Compare a TDI to a Golf with the 2.SL0 and get back to me, not to my current Mercedes. And then compare one to the non-turbo 1.4 that would have gotten you similar economy on the other side of the pond, but only if you drove it really, really slowly.
If you drove one that was loud and clattery, you drove one that was broken.
My best friend had the diesel in his 2011 Outback and sold it at 400,000kms and original CVT (which he did not get serviced) and needed the dpf renewed at the end but was a perfectly cromulent diesel vehicle.
All truly horrible diesel engines originated from gasoline engines which were converted to diesel using “clever” cost saving engineering. This practice is what truly killed the diesel passenger car in America.
A Diesel’s block and reciprocating assembly experience much higher forces than their gasoline equivalent, so there’s no getting around the fact that things need to be beefed up considerably.
When I read that the engine was actually lighter than it’s gasoline equivalent, I knew right away that they must have forgot to put something in there.
I don’t know any more about diesels than what I’ve read here (well, almost), but that’s definitely a common thread I’m seeing in the YADF (Yet Another Diesel Fuc.. Failure) stories.
I remember when these were announced, I was a youngin and the internet was a buzz of a “WRX Diesel” and other crazy ideas on the forums. Distinctly I remember folks saying “If they can’t figure out how to do head gaskets, how can they do a diesel?”
Seems they were right.
So, depending upon how you classify “production”, there were horizontally-opposed diesel engines used by the US Navy back in WWII. The USS Pampanito had, I think, a 10-cylinder one (it’s a cool ship to visit, moored in Fisherman’s Wharf in San Francisco).
Opposed piston means there is a crankshaft and piston at both ends of the cylinder. The air is compressed by the pistons coming towards each other. ,,,and they were vertical not horizontal. Not really comparable to the boxer engine Subaru is claiming to be first with.
https://www.dieselduck.info/machine/01%20prime%20movers/fairbanks_morse/fairbanks_morse.htm
Ah, fair enough. I was going off of memory, and unsurprisingly my bad memory was faulty.
Don’t forget the Napier Deltic!
It stinks that this was an engineering dead end for them. I can imagine a manual Forester with the diesel would be a great do-it all vehicle if the engine was easy to maintain.
This does kind of explain why they were so late to the hybrid party too though.
I remember following this closely. I couldn’t understand why they had to make a boxer diesel I had figured they would do a deal with some engine manufacturer for a diesel model in the US but just watched as they went into insanity and then launched everything with a cvt but no diesel. I used to see the Subaru branded robin engines at different places. At one point harbor freight had Subaru robin branded gas engines. The diesel generator and other things were at alot of places that sold and rented equipment.
Particularly as Subaru was in GM’s sphere of influence during development (they bought a 20% stake in FHI in 1999, sold almost half to Toyota in 2005, then sold the rest back to FHI in 2006). You would think maybe they could have gained access to the GM/Fiat Multijet program
But, I suspect it was twofold, 1) boxer engines being seen as an important unique characteristic of the brand, and 2) wanting to make sure it would fit in the engine bays of existing models with no real structural changes
I was told by an automotive engineer and an automotive environmental engineer that the EPA spec was harder to meet then the euro spec at the time. They blamed the lack of many American market diesel cars on that. It was probably true especially with the whole diesel gate thing happening. GM even said they didn’t know how VW was doing it.
It seems like an engine cradle for a small enough diesel would have worked weight distribution could be an issue for sure.
The Euro emission specs were geared more towards lower CO2 (greenhouse gas), while EPA emissions spec was more concerned with NOx (health reasons).
Diesels emit less CO2 than gasoline engines, but more NOx, so diesels have to be “cleaner” in the US, and lowering both CO2 and NOx are somewhat contradictory goals (one needs higher combustion temps, the other lower), which is why SCR & urea injection was a must.
Aside from BRZ, Subaru’s entire U.S. product line since 1990 has been based on just two platforms, SI and SGP. Both designed for boxers only. And of course the boxer layout for a long time let Subaru implement AWD at little extra cost.
Subaru did make inline engines for a long time, but they only went in very small vehicles, like the kei cars.
My 1997 Polaris 4-wheel ATV has a Subaru Robin 2-stroke engine. It’s been a superb machine.
I always forget Polaris had diesels in the civilian world. Always think of those artic cats diesels. I road one once and it was not great idk who made the engine for them.
I remember following it as well. I really wanted to buy a Legacy wagon with this engine, as the 2005+ Legacy wagon was downright handsome (sans Outback trim) and may be the only attractive Subaru ever made. Alas, the engine was in perpetual rumor mode for the US so I bought a Jetta wagon instead. I never regretted that decision, but AWD would have been nice.
I did the same but sedan. I thought the legacy would have been the prime model they would throw a diesel in.
Some of it was brand identity, but mostly fitting it (which also relates to fitting in regards to the non-negotiable retention of their “symmetrical AWD”). The boxer engine is longitudinally mounted and short. Whatever close equivalent they’d outsource would be an inline 4, which would be too long and stick out even further ahead of the axle (plus heavier), making handling worse if packaging of the cooling system and condenser due to the increased engine length could be resolved. Another issue may have been height interfering with the hood/space above the head needed to meet Euro pedestrian safety. Also—and this isn’t huge, but still a cost consideration—whatever they’d source would almost definitely be designed for a transverse application, so some parts would have to be redesigned, not that the idea would get that far.