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Subaru debuts third-generation boxer four-cylinder engine

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Filed under: Technology, Subaru

Subaru's Third-Generation Boxer Engine - Click above for high-res image

Boxer lovers, the next chapter in your love affair has just begun. Fuji Heavy Industries, parent company of Subaru, has introduced the latest, third-generation boxer engine that will relieve the second-gen after 21 years of service. This is a brand new lump, not a rework, and FHI has built a factory just to produce it.

The bore and stroke have been increased, and it will be available with four cylinders in 2.0- and 2.5-liter displacements. The intake ports have been redesigned, lighter pistons and connecting rods offer reduced internal friction, and separate cooling circuitry for the block and the head are some of the changes that have resulted in a lower emissions and a ten percent increase in fuel efficiency. No power figures are being quoted yet, so we'll have to see how it measures up when it finds its way into production engine bays.

This new boxer will be Subaru's primary engine, and will first be seen in the Forester. Follow the jump for the press release, and you can have a closer look at it the high-res image below.

[source: Subaru]

Continue reading Subaru debuts third-generation boxer four-cylinder engine

Subaru debuts third-generation boxer four-cylinder engine originally appeared on Autoblog on Thu, 23 Sep 2010 11:32:00 EST. Please see our terms for use of feeds.

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Subaru Announces First All-New Boxer Engines in 21 Years


Fuji Heavy Industries Ltd. (FHI), Subaru's parent company, has released details on its third-generation four-cylinder boxer engine that will be available in 2.0-liter and 2.5-liter displacements. This is the first overall renewal since the second generation was introduced in 1989. The horizontally opposed flat 4 has been a mainstay of Subaru's Impreza, Forrester and Legacy models for some time.

Subaru claims that fuel efficiency is up by 10%, thanks to a compacter combustion chamber and longer stroke, variable-valve timing (which Subaru calls Active Valve Control System) on both the intake and exhaust valves, lighter pistons and connection rods, a more efficient and compact oil pump and separate engine cooling circuitry for both the block and head.

Power for the 2.0 L engine remains the same at 109kw / 150HP, while torque is up 5 Nm to 196.

The new boxer engine has a slightly higher compression ratio of 10.5 (up from 10.2), a shorter bore (84 mm, down from 92) and longer stroke (90 mm, up from 75). Subaru has yet to release details about changes to the 2.5-liter unit.

The first Subaru to receive the third-generation boxer engine will be the Forester at an, as of yet, undisclosed time.

By Tristan Hankins



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By Mark Kleis

Subaru today proudly announced the unveiling of its latest and third-generation four-cylinder Boxer engines, in both 2.0-liter and 2.5-liter displacements.

This latest generation marks the first major refresh of the engines in 21 years, marking both a tribute to the forward thinking of the original design, and the need to update the engine as emissions and power requirements continue to develop new standards.

Subaru says that the third-generation Boxer engine has been rejuvenated from the ground up, retaining only the basic design of the horizontally-opposed layout. The changes have resulted in an approximate increase in fuel economy of 10 percent, as well as increased smoothness and an improved power band. More specifically, the bore and stroke have been modified to allow for a more compact combustion chamber, as well as a longer stroke.

These two changes were previously impossible due to the chassis mounting locations. Other changes include the optimization of intake and exhaust valves, with the intake side receiving an intermediate lock system which allows valve timing to be advanced or delayed for more precise control over intake and exhaust valve timing - all of which contributes to improved overall engine performance from both power and emissions output perspectives.

The latest Boxer engines also received improved cooling by adding a separate engine cooling circuitry for the block and head, as well as the use of lightweight pistons and rods, along with a highly efficient oil pump that creates a 30 percent reduction in friction loss.

The 2.5-liter variation retains the same 170 horsepower rating, albeit with peak power at a slightly lower rpm, while torque improves from 170 lb-ft at 4,400 rpm to 174 lb-ft at 4,100 rpm.

The engine was also designed in a way that is as forward thinking as the original design, with the intention of allowing future changes to be implemented without a major redesign as environmental standards continue to evolve.



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I've always liked Subaru's engines. Not exactly happy to rev, but always feel torquey and have a nice grunt to them.

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