A Better B4

Chris Clark has had a true love-hate relationship with his car - a locally-delivered Subaru Liberty B4. Sure he loves it now, but the relationship was very strained not so long ago...

After enjoying ownership of a couple of Subie Impreza WRXs, Chris was one of the many people who were holding their breath for the release of the 'awesome' B4 twin-turbo. So when the twin-turbo Lib finally arrived in late 2001, Chris was one of the very first people peering in through the window of his local Subaru dealership. Having read various magazine road tests praising the super Subie, Chris was just itchin' to go for a test drive. Unfortunately, though, the local dealership had already presold their B4s and all he could manage was a close-up optic and a sit inside. Still, this was enough for Chris to sign up for his own B4; he'd made a conscious decision to ignore the hard-core Impreza STi (which had an identical $55,130 price tag) in favour of the more sophisticated B4.

A few weeks down the track and just minutes after taking delivery of his new Subie, Chris realised he shouldn't have signed anything without first going for a test drive. Out on the road, the B4 wasn't the sort of car he thought it was - it wasn't really 'big brother' to the WRX at all. "I guess I was sucked in by the bullsh*& in those car mags (he obviously hadn't read the AutoSpeed B4 review!) and I just kept thinking to myself, what have I done?"

The biggest problems were the massive torque hole during the transition onto the secondary turbocharger (the B4's twin-turbo system is sequential) and a general lack of all-out power; the Australian-delivered B4 manual is detuned from the Japanese-spec 206kW to just 190kW.

Fuming about the situation, Chris had made a couple of visits to Paul Brell of Sydney's BD4s; Paul had successfully tweaked Chris's (now-sold) MY99 WRX. "I had a few big whinges there and Paul convinced me to try changing a few things." And thank God he did!

Before making any underbonnet changes, however, Paul decided to first see what he was up against; time to hit the chassis dyno. Chris had stressed how terrible the B4's engine characteristics were, but - still - Paul couldn't believe the torque drop-off he saw as the second turbo was brought on-stream; "it's pretty disappointing from a major car company" he says.

Strapped onto the dyno rollers, it was also discovered that the B4 was highly sensitive to temperature build-up - after only one or two 'stabilisation' runs where up to 124kW was seen, power plummeted to a pathetic 98kW at the wheels (measured in third gear on a Dyno Dynamics AWD chassis dyno). Paul tells that the car was pinging and its ECU was going into some sort of massive ignition retard mode.

Needless to say, given its poor torque curve and lacklustre total power output, Chris's B4 was going to be a pretty big project!

The first mods involved the fitment of a 75mm diameter cat-back exhaust system. With BD4s being an Australian HKS dealer the exhaust is, naturally, HKS. Like most brand-name aftermarket Japanese go-fast gear, the exhaust is beautifully made though Chris says, despite its centre resonator and rear muffler, it is a tad too loud for his tastes. "On the road the exhaust made a bit of difference" tells Chris, "but not appreciably, if you know what I mean".

Gas flow into the two IHI turbochargers was then enhanced with the fitment of a HKS extractor manifold, which uses 42.7mm diameter stainless runners. Again, these look like top-notch bits of gear.

Next up, the factory top-mount heat sink (otherwise known as an intercooler) was flicked to make way for a HKS front-mount intercooler kit. As Paul says, "the big advantage of the front-mount is it gives more consistent performance in different temperatures and driving conditions". This was a straight bolt-in, however it did require replacing the standard airbox with a HKS 'mushroom' filter.

And what did these mods achieve? Well - as seen in this graph - the drop-off during the transition onto the secondary turbo was improved but, strangely, peak power went virtually unaffected. One-twenty-four kilowatts was all it could muster; at least it didn't fall away to 98kW after a couple of runs like it did before.

The kilowatt tally shot up, though, when a HKS airflow meter controller was wired in. This allowed Paul to richen the air-fuel mixtures in a few critical zones and safely wind up the boost a tad. Manifold pressure now peaks at 1.1 Bar thanks to a pair of Turbosmart bleed valves, which also serve to further improve drivability.

As seen in this graph (with boost pressure now set to 1.1 Bar) power is now up to 170kW at the wheels; an improvement over standard of more than 37 percent! Note, however, these latter figures were recoded on a different workshop dyno to that used in the first instance (still a Dyno Dynamics unit though). "From this point on I've been pretty happy" says Chris, "the car is now worth owning and, further, I was more than happy with BD4's workmanship and attention to detail".

With the troublesome twin-turbo boxer engine now sorted out Chris thought it worthwhile to treat the car to some tasty wheels and improved suspension.

As evident in our pics, the front-end has been lowered 1 ½-inch and the 1-inch at the rear thanks to King springs, while beefier 20 and 22mm front and rear swaybars are bolted beneath. The standard Bilstein inverted dampers are good enough to remain in service.

The standard Oz-spec brakes, though, were pretty borderline with the newfound speed so Paul sourced a second-hand set of MY99 WRX 4-pot front calipers and ventilated discs. After a quick disc machine and caliper overhaul, these bigger anchors were a straight bolt-on conversion - gotta love that. Brake pads are the kind-on-discs 'road' compound produced by HKS.

As we commented in our B4 road test, the early Liberty B4 rims - 17-inch BBSs - are a bit too lacy and fussy looking to suit the rest of the car. Chris has fixed this with some gorgeous 18 x 8 Racing Hart rims clad in big-as-would-fit 225/40 Falken rubbers; talk about giving it a personality transplant!

Beyond its lowered stance, big-ass rims, window tint and big-bore polished exhaust tip, the aftermarket influence of Chris' B4 is fairly covert. Only dedicated B4 fans will pick the new mesh in the lower front bumper aperture (with the HKS 'cooler just visible behind) and the Skyline GT-R style cutouts on both sides of the number plate; both of these measures are intended to maximise cooling airflow through the front-mount core. The sole remaining purpose of the standard bonnet scoop is to keep a lid on under-bonnet temperature.

Although the standard B4 didn't drive like he expected, the luxo leather-lined interior is certainly all it's cracked up to be. With backlit instruments, a brilliant McIntosh sound system and plenty of seating comfort, the only necessary addition for this car is the HKS airflow meter controller (hidden in the glovebox) and a HKS boost gauge on the driver's A-pillar. Add anything else and it'd ruin an already good thing.

So - now with over 37 percent more power and its sequential turbo operation ironed out - Chris is now quite content with the car; but not before nearly selling it, mind you. "The way it is now is exactly what Subaru should have given us in the first place; a B4 with more power, better drivability and greater braking capacity". He declares "at least now I get to enjoy the bloody thing..."

A definite case of love-hate...

Contact:

BD4s
+61 2 9879 3322

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