FHI Details World's First Horizontally Opposed Diesel for Passenger Cars

Feb 22, 2008
Kenji Momota, Journalist
Horizontally opposed diesel engine "EE20"
Horizontally opposed diesel engine "EE20"
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Cylinder block
Cylinder block
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Piston
Piston
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Crankshaft
Crankshaft
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Con Rod
Con Rod
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Injector
Injector
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Common rail
Common rail
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Turbocharger
Turbocharger
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Satoshi Maeda (left) and Toshio Masuda (right)
Satoshi Maeda (left) and Toshio Masuda (right)
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Fuji Heavy Industries Ltd unveiled the technical details of "EE20," the world's first horizontally opposed diesel engine for passenger vehicles, Feb 19, 2008.

Some test-riding events for mass media were held for Subaru's Legacy sedan equipped with this 2.0-liter diesel engine in various parts of Europe, beginning in Spain in January 2008. But, in Japan, this is the first briefing session on the EE20.

The vehicles equipped with the EE20 will be officially announced March 4, 2008, at the 2008 Geneva Motor Show. And the Legacy sedan, wagon and the Outback equipped with the EE20 will be released on the same day. The diesel engine is planned to be mounted in other models. But it has not been announced when the engine will be introduced in North America or Japan.

Fuji Heavy Industries spent about three years to develop the EE20. The features of the engine are its lightness, smallness and rigidity. The total length is 353.5mm, 61.3mm shorter than "EJ20," the company's 2.0-liter natural aspiration gasoline engine. The bore pitch is 98.4mm, the same as that of "EZ30," the company's six-cylinder engine. The EE20 and EZ30 are produced in the same assembly line of the company's Ooizumi Factory.

Fuji Heavy Industries did not reveal the mass of the EE20, but it is about 10kg lighter than the inline four-cylinder diesel engines developed by companies in Europe. 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.

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.

Commenting on future emission regulations such as Euro5, Satoshi Maeda, the company's general manager of the Engine Design Department, said, "We will not change the basic hardware. But we can comply with those regulations by using a closed DPF instead of an open DPF and optimizing the EGR cooling system. We will adopt a multistage injection system for the injector and consider employing a piezo system."

The Legacy and Outback mounted with the EE20 are equipped with a clutch whose dual mass flywheel and damper property were modified for diesel engines. The clutch is combined with a five-speed stick shift. The company considers using a six-speed stick shift in the future but not an automatic shift at this point. The gear ratio of the transmission was changed for the engine whose torque is strong at low revolution.

To reduce the vibration and noise, Fuji Heavy Industries added various insulators. For example, sound insulators were installed inside the fender, and damping materials for the floor panel were doubled. For the diesel Legacy, the company changed the engine mount from a solid engine mount designed for gasoline engines to a liquid-filled engine mount.

In addition, the company employed an electric power steering as it did for the new 2.0-liter Forester for Japanese market. And it adopted a 16-inch front brake and sized up the outer joint of the front drive shaft.

"We had many thorough tests in the autobahns and various urban areas in Europe to realize a performance worthy of Subaru brand," said Toshio Masuda, the Legacy's project general manager of the Product Planning Department. "As a company that developed a diesel engine last, we elaborated the balance between the sportiness and mileage."

Specifications of the EE20

Name EE20
Displacement 1998cc
Maximum output 110kw(150PS)/3600rpm
Maximum torque 350N·m/1800rpm
CO2 emission 148g/km
Compression ratio 16.3
Bore × stroke 86.0 × 86.0mm
Bore pitch 98.4mm
Bank offset 46.8mm
Deck height 220mm
Journal diameter φ67mm
Pin diameter φ55mm
Rod center distance 134mm
Piston pin diameter φ31mm
Compression height 43.0mm
Fuel injection system common rail
Turbocharger variable nozzle turbocharger
EGR water cooled
DPF open
Total length 353.5mm