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Subaru Liberty B4 Twin-Turbo

Evaluating Subaru's latest high-performance special - the 190kW twin-turbo Liberty (Legacy) B4.

By Michael Knowling

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Mention twin-turbos and most people assume you're talking about a car that's completely devoted to raw power. The Subaru Liberty B4 is much less of an animal - instead its twin-turbos are aimed purely at driveability.

Twice As Good?

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The newly released Liberty B4 is powered by an EJ20B 69H - a turbocharged, intercooled, DOHC, 16-valve, 2-litre boxer four, which is of the same basic design as the engine found in WRXs and the Liberty RS of ten years ago. Internal developments have resulted in reduced valvetrain mass and an increased compression ratio (up from 8.0 to 9.0:1), and Subaru has endowed the B4 with two sequentially-staged turbos in order to maintain a good spread of torque. The Australian-delivered Impreza STis used a single turbo and made more power than the Liberty - 206kW versus the B4's 190kW at 6400 rpm - but they didn't offer 278Nm at a mere 2000 rpm or a 320Nm peak at 4800 rpm.

The B4's focus is on response and flexibility in everyday conditions.

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The hottie Liberty is set up to offer good throttle response and backs it up with a strong surge of torque anywhere in the rev range. The primary turbocharger is arranged to quickly deliver boost up to 4000-4500 rpm, with the secondary turbocharger then kicking in to add flow in the higher ranges. It's a cunning system - but is it perfect?


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During the transitional phase - where the secondary turbocharger is starting to pump in addition to the primary unit - there's an ugly 'hole' in the torque delivery. Under full throttle, a significant dip in manifold pressure identifies the 4000-4500 rpm transition; we measured a full 0.25-0.3 Bar boost pressure dip.

It's enough for first-time passengers to ask if there's an engine problem....

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Similar to the high-strung STi Imprezas, the B4's on-road performance is very dependant on intake air temperature. With seat-of-the-pants telling us heat soak r-e-a-l-y took the shine of acceleration, we again stuck on a boost gauge to see how the B4 reacted to increasing intake temperatures. With low ambient temperature and barely any under-bonnet heat soak, we saw a 0.95 Bar peak boost figure in the mid-range, dropping to 0.75 Bar in the top-end. But once heat soak set in after a couple of runs, peak boost slipped to 0.8 Bar and top-end boost remained around 0.70-0.75 Bar. Obviously, Subaru has come up with conservative ECU mapping aimed at avoiding detonation.

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Fuel octane is another factor that can lead to detonation; for the B4, official Subaru literature suggests a "minimum required octane rating" of 98-RON. Unfortunately, this ultra high-grade fuel can prove difficult to locate when you venture far from a major city. It's just as well the B4 has a 64-litre fuel tank and - on average - sips around 10 litres per 100km.

But now to the kind of performance that really matters - acceleration.

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With its strong spread of torque, the B4 is a deceptively quick sprinter away from the lights. Easing off the line and then mashing the loud pedal sees the Subie hit 100 km/h in a shade over 7 seconds, or a full-on launch will get the job done in a claimed 6.5 seconds.

These sorts of acceleration times can partly be attributed by the traction of Subaru's long-standing viscous AWD system. With drive taken by a relatively lightweight clutch and a nice short-shifting 5-speed 'box, the B4 apportions torque front-to-rear depending on the rotational speed difference between the front and rear wheels. Traction is also aided by a rear LSD.

Predictable, Safe Handling...

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Combining with AWD is the B4's lowered Bilstein struts, which offer an excellent combination of ride quality and handling. Despite being set up quite firmly, the car manages B-grade public roads without any nasty surprises - though small-amplitude, high-frequency bumps induces slight patter. This goes away at high speed, where the B4 shows itself as a truly wonderful machine. The well-weighted, precise steering allows you to place the chassis wherever you want and it won't budge from that line. It just grips and grips and grips.

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At urban speeds, however, the B4's handling isn't as impressive. Its extra size means it'll never be as 'flickable' as an Impreza WRX, and it'll go into a front-end push if you're too ham-fisted with accelerator or steering inputs. One major advantage, however, is that the B4 can be throttle steered; the response of the sequential turbos allows you to add and subtract just the right amount of drive. Unlike its single turbo cousins, there's no having to floor the accelerator early in the corner in the hope that enough torque will arrive to haul you out...

If you approach a corner a little hot in the B4, you can depend on its powerful ABS brakes to bring things back into line. The 294mm ventilated front discs are effectively pegged by twin-pot calipers, while the rears use 290mm ventilated discs and single-pot calipers. We didn't experience any brake fade during our road test.

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Aerodynamically, the Liberty feels stable - but not to the same degree as, say, an Evo, GT-R or even the STi Impreza. This can be put down to the B4's subtle, wing-less bodylines - the only difference over the Liberty RX's panels is a small bonnet scoop (inset into a light weight aluminium bonnet). Carried over from the rest of Liberty line-up are side skirts, a rear spoiler and a fog light'd front bumper.

Perhaps due to the lack of wild aero add-ons, the B4 is an elegant vehicle; unblemished thanks to an integrated aerial, flush-fitting glass and swoopy halogen headlights. The 17 x 7-inch forged alloy BBS wheels with 215/45 Bridgestone Potenza RE010s and the slight lowering of the Bilstein suspension make all the statement that's needed.

A Comfortable, Functional Environment...

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Like most contemporary Subarus, the B4 offers good space utilisation. There's plenty of stretching room in the front, and the back's pretty reasonable - though footroom is minimal and headroom is slightly low. The boot is a good size and shape, although the rear seat doesn't fold forward - instead there is a ski port. Everything in the cabin is very well laid out, the instruments and controls fall to hand and don't require that you take your eyes off the road to make interpretations.

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When we first jumped in, we were a little sceptical about the backlit instrument cluster - this type almost always looks trick, but rarely performs as well as conventional instruments. Therefore, we were happy to discover that the B4's do work really well - they don't get flared by sunlight, you can view the display through sunglasses and they offer a very high contrast. Top marks.

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Another area where the B4 scores highly is its sound system. With a McIntosh single CD/tuner/cassette system 'tuned for Subaru', you'll enjoy a full spectrum of sound and zero distortion. SPL from the seven speakers (including a single rear deck woofer) seems quite high for an OE fitment.

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To ensure the B4 appeals to a separate market to the WRX, the B4 comes with standard leather trim - but it's too bad if you don't like its combination of black and blue/purple! A few years from now, this will be a trim everyone will look at and go "ugghhh". Black leather also covers the Momo steering wheel, gear knob and handbrake lever. Seating is soft but very comfortable, there's adequate side support and driver's seat features 6-way electric adjustment. We felt a bit ripped off, however, to discover the electric adjustment applies only to the bottom cushion - you have to manually adjust the backrest.

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Other standard items include electric windows and mirrors, digital climate control, a total of four cup holders, illuminated vanity mirrors, map lights, specific door ajar indicator and twin trip meters. The only notable omissions are a trip computer and - oddly enough - cruise control. Even the Liberty RS of 1992 scored standard cruise control, Mr Subaru - what happened?

But the B4 has one saving grace that goes a long way to making up for any of its shortcomings - its price.

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With recommended retail set at $55,130 (plus dealer and statutory charges), the B4 is a true bargain. It'll be stealing sales from the VW Passat V6 4Motion, Holden/HSV Gen 3 Commodores, Ford Tickford TE50, Volvo S40 T4 and S60 2.4T, Mitsubishi Magna Sport/VRX, Peugeot 406SV, Saab 2.0 Aero 5-door, BMW 325i and, perhaps, Subaru's own WRX. If you decide you must have a B4, the only option is paint colour - chose from white, deep blue mica, black or metallic silver (the metallic costs extra). Like all Subarus, the appeal of the B4 is further sweetened by a 3 year/100,000km warranty and what we foresee will be excellent retained value.

The B4 might not be a true supercar - but take into account its price and what it offers and you'll find it hard to go past.


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Subaru Australia

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