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The Subaru Six-Cylinder Engine Guide

The evolution of Subaru's under-rated six-cylinder engines

By Michael Knowling

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At a glance...

  • At a Glance:
  • Guide to Subaru six-cylinder engines
  • Mechanical specs
  • Power and torque figures
  • Driveline configurations
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Subaru has become popular in performance circles largely thanks to its rally-proven EJ20 2-litre turbo engine. But the Japanese company is also more than capable of building some damn fine six-cylinders – with up to 184kW available from a beautifully free-spinning 3-litre six, there’s a whole world of Subaru performance engines that go barely noticed.

So let’s sit up and take notice!

Early Subaru 6s

The first six-cylinder engine manufactured by Subaru appeared in the 1989 model year – at around the same time the EJ20 four-cylinder turbo was born.

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As the boxy looking Alcyone (aka Vortex) coupe neared the end of its life, Subaru quietly introduced a six-cylinder version as an option to the existing four-cylinder models. The six-cylinder Alcyone was intended as the sophisticated, top-of-the-line version and was sold with a standard four-speed auto and constant AWD.

Interestingly, the new six – coded ER27 – is essentially a Subaru EA82 four-cylinder with a couple of extra pots. It’s a horizontally-opposed design and the block and heads are made from aluminium. Bore and stroke dimensions are 92 and 67mm respectively (identical to the EA82) and total swept capacity is 2672cc. With relatively plain SOHC heads, a 9.5:1 compression ratio, multi-point fuel injection and a distributor ignition system, the ER27 is rated at 112kW at 5200 rpm and 211Nm at 4000 rpm. This is achieved on normal unleaded fuel. The ER27 engine was seen in the Japanese domestic market and America only.

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The six-pot Alcyone went relatively unnoticed until the formula was reinvented for the 1991 release of the Alcyone SVX (known as simply SVX in most counties). The SVX brought much more stylish lines and, as a result, the car received more attention. Under the bonnet lives a new all-alloy EG-series six-cylinder engine – the horizontally-opposed EG33. At 3.3 litres (with a massively over-square 96.9mm bore and 75mm stroke), the SVX engine holds a significant capacity advantage and benefits from DOHC, four-valve-per-cylinder heads. A dual-stage induction system is also incorporated to improve the spread of torque.

In Japanese spec, the EG33 puts out an impressive 179kW at 6000 rpm and 309Nm at 4000 rpm. Its 10:1 compression ratio requires premium unleaded but there are twin knock sensors to alter the timing of the direct-fire ignition system. Australian delivered versions are detuned slightly to 172kW at 5600 rpm and 304Nm at 4000 rpm. Sales of the SVX dribbled through until 1997.

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Like its predecessor, the EG33 is engineered for longitudinal mounting and comes tied to a standard four-speed AWD transmission. This is a top-notch engine that, even by today’s standards, puts out excellent power and torque. It also remains the largest engine produced by Subaru. Note that the EG33 also has many similarities with the EJ-family four-cylinder – the EG33 shares the same bore and stroke dimensions as the EJ22.

Late Subaru 6s

Subaru took a break from six-cylinders during the late ‘90s but released a newie in 2000.

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Introduced in the Japanese-spec Subaru Legacy Lancaster 6 wagon, the new-generation six-cylinder is coded EZ30. The EZ30 has a more balanced bore/stroke ratio (at 89.2 and 80mm respectively) and swept capacity is 2999cc. Interestingly, minimising the distance between cylinders and switching from a belt to a chain cam drive helped Subaru reduce the length of the six-pot engine – it’s just 20mm longer than the EJ-series four cylinder! Again, the EZ30 uses DOHC, multi-valve breathing and a variable induction system. With a compression ratio elevated to 10.7:1 (requiring the use of premium unleaded fuel), the EZ30 outputs 162kW at 6000 rpm and 289Nm at 4400 rpm. A four-speed auto comes standard – with trademark Subaru AWD, of course.

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The same EZ30 engine was released in the Australian-spec 2000 Subaru Outback H6 but output is choked down to 154kW at 6000 rpm and 282Nm at 4400 rpm. We believe this output is achieved on normal unleaded fuel.

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In 2002, the Japanese market EZ30 was given the tweak it really needed to be taken seriously as a high-performance engine. Subaru treated their 3-litre motor to AVCS+ continuously variable inlet valve timing (across a 50- degree range) along with variable valve lift. VTEC style! Cam switching occurs between 2000 and 4000 rpm depending on load. Retaining the base engine’s 10.7:1 compression ratio, the newly created EZ30-R engine screams out 184kW at 6600 rpm and 304Nm at 4200 rpm. This engine is reserved for top-line versions of the 2002-onward Legacy wagon, Outback and B4.

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The EZ30-R can also be found from late ’03 in the local Outback 3.0R where it delivers slightly less grunt on 95 RON fuel – 180kW and 297Nm. A five-speed auto trans is also adopted in place of the previous four-speeder. In 2004, the Liberty 3.0R sedan and wagon was introduced sharing the same driveline. A six-speed manual was also offered in the Liberty range.

Obviously, the EZ30-R engine is the hot choice in the Subaru six-cylinder line-up but, given its age, we’d expect these engines to be very expensive at the import wreckers - not to mention rare (we are yet to see one). If you want maximum bang for buck, you can’t go past the big-cube EG33 from the SVX – with 179kW in Japanese guise, these engines are perfect for conversions into Subaru Liberties/Legacies. Oh, and they’re also dirt cheap because it seems nobody wants ‘em – we’ve seen a complete SVX half-cut at an import wrecker for around AUD$2000!

Now, the next logical step is to create an EG33 turbo...

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