The Subaru Liberty RX 2.5-litre is a fantastic all-round car - take a flick through any contemporary road tests and you'll quickly recognise that. Melbournian Albert Lin certainly agrees that the RX is a great all-rounder, but - arghhh - he says could do with a fair dollop more power.
After taking delivery of his MY00 Liberty RX, Albert was happy enough to jump in and out of the driver's seat on a day-to-day basis and admire the Subie's feeling of security, quality and comfort (the optioned leather seats helping the cause). When the throttle went down, however, the throbby flat four failed to excite - I suppose that's what you've gotta expect in a 1400kg car with only 115kW and 223Nm.
Only months after he purchased the RX, Albert was flabbergasted by the release of the twin-turbo Liberty B4 variant. Oh, if only the 190kW B4 had been available earlier! Albert decided to test-drive a new twin-turbo beastie with the view to potentially trading-in the ol' RX. Interestingly, though - like us - Albert couldn't get r-e-a-l-l-y excited over the B4. Yes, it was quicker than the RX 2.5, but it was not enough to light his fuse.
The faithful RX was kept.
After persevering with its 115kW for about a year, Albert then had a quiet word to Mr Dean Ong of Technik Tuning. Albert had already heard on the grapevine that installing an exhaust, intake and UniChip to the RX gives around 145kW, but - no - this 26 percent gain wasn't going to satisfy. Albert wanted even more power, but - at the same time - he insisted on maintaining driveability and a beefy torque spread.
Dean answered the call by suggesting a turbocharger fitment to the standard engine. As Dean explains, "keeping the standard compression ratio keeps good off-boost torque." Of course, it also saves the expense of a turbo-specific engine rebuild.
After a little bit of chin stroking, Albert gave the idea the go-ahead.
Dean selected a TD04 turbocharger from a late-model WRX as the basis for the system. Producing a modest 160kW on the factory EJ20 turbo, this particular 'charger is the ideal size to ensure minimum lag. Top-end power wasn't seen as the be-all.
The TD04 was bolted to the engine using the standard EJ25 exhaust manifolds, with a custom pipe leading up to locate the turbo similarly to the Subaru EJ20 turbo. Interestingly, Dean tells us the exhaust manifolds off a DOHC EJ20 turbo wouldn't fit the SOHC 2.5 without some fairly major modification.
The rest of the RX's exhaust system was also upgraded. There's now a 2?-inch mandrel system from the back of the turbo, equipped with an aftermarket high-flow cat, two resonators and a 5Zigen style rear muffler. The relatively small pipe diameter (compared to 'the usual' 3-inch) and the line-up of muffling devices ensure this Subie is quiet and drone-free.
Feeding intake air to the compressor side of the turbo is a K&N pod filter on the end of a large diameter induction pipe. Note that the EJ25 is factory equipped with a MAP sensor load signal. Cool intake air is fed to the K&N through a duct inside the guard. Note also the TurboSmart blow-off valve, which catches your eye second to the filter.
Mindful of the standard 10.0:1 compression ratio, Dean has kept boost pressure down to the wastegate setting of around 0.5 Bar. With this relatively small hit of heat to combat, the top-mount water-to-air intercooler (pinched from an import '90s Legacy RS turbo) performs very competently. At the time of photography, however, the core's water plumbing system was yet to be installed. Albert's now sourced a marine-type 12V high-flow water pump, and there's a front-mount radiator ready to be whacked in.
This'll safely enable some extended boost runs!
To keep pace with the turbocharger fitment, the fuel delivery system was up-spec'd accordingly. Initially, a combination of STi injectors, a Bosch Motorsport pump and an ART-brand fuel pressure reg (complete with gauge) were installed to achieve closer-to-correct mixtures but, unfortunately, the result wasn't very effective. To improve this situation, a UniChip interceptor module has since allowed some further tune-ability - more on this later.
Backing the turbocharged 2.5 is the standard 5-speed AWD gearbox. Torque is channelled through a lightened flywheel and an Exeddy 5-puck clutch (the standard clutch began slipping almost straight after the turbo went on). The rest of the driveline remains standard.
While this five weeks of build-up madness was happening, Albert also decided to have a better looking set of wheels slid on. These are 18-inch GP Turismos clad in 225/35 Falken liquorice - the rims blend in nicely with the colour of the car, don't they? You may notice the ride height has also been brought down a couple of inches - this has recently been achieved using King springs. As Albert tells, "the standard car handled very well, it just sits flatter now."
Hiding behind those bigger wheels are bigger front brakes. Recognising the significant power increase, Dean fitted MY99 STi 4-pot calipers, which bolted straight onto the standard hubs. Dean's ART pads are used all-round.
With just the intercooler system awaiting completion, we took Albert's boosted RX on a quick drive along a quiet road. The first impression was, "Wow, this thing's got so much response and bottom-end torque!" Certainly, the turbo'd 2.5 can be short-shifted, completely unlike the factory 2-litre EJ20 turbo - not surprising considering the full 0.5 Bar boost arrives as early as 2000 rpm! Mid-range torque continuers to snowball impressively, but - unfortunately - things got a bit ragged from there on.
Blame that on mega-rich mixtures. "There's too much fuel going in at the top-end," explains Albert, "it also uses a lot more fuel that it used to."
At present, Albert's looking closely at moving to a high-quality aftermarket management system - probably either an Autronic or a MoTeC. This will give the tuning flexibility to iron out the air-fuel ratios and optimise ignition timing. "It will also give the foundation to control the water-to-air intercooler pump and anything else that might be added," he adds.
Speaking to Dean, it seems quite likely that the boost control function of either of these ECUs will also be used to pump in a few more psi. That done, Albert can't wait to line up somebody's 'awesome' B4!
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