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This article was first published in 2001.
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The path to enhanced WRX performance is becoming a well-trodden one. Boost, intake, exhaust, turbo - they're all effective at taking the already scintillating performance of one of our favourite cars to the next plane. But what if you want something different? And what if at the same time you'd also like to retain factory reliability and fuel consumption? Well, there is an alternative - and it's one that can be applied to any four-wheel drive Impreza, not just the Rex.
So what are we talking about? No less than dropping the Japan-only twin turbo Liberty engine into its smaller brother!
The Liberty (Legacy in markets outside of Oz) and the Impreza are very closely related. In fact, the engine bays of both cars are near identical in terms of their shape and dimensions. A bit like with Nissan in the Seventies and Eighties, for cost reasons Subaru has made many parts interchangeable. Why re-invent the wheel if you already have one sitting on the shelf that can be put into application in a new car? So not only can bits from Liberty and WRX motors be swapped, but also whole engines. In fact, as you prob already know, the WRX was created by Subaru stuffing a slightly modified Liberty RS engine into the smaller and lighter Impreza shell. That produced a car which.... well, you already have heard chapter and verse on how the Rex has changed the performance world.
But back to the car pictured here....
Tony Rigoli Performance on the Gold Coast is the acknowledged Australian WRX performance king, with their blisteringly-fast in-house car backed up by a huge array of daily street-driven customer machines of only slightly lesser specification. Cars with hybrid T3/T4 turbos, cars with bigger capacity than standard engines, and cars with a whole raft of mods abound in their workshop. And, talking about their in-house drag-orientated car, Dominic Rigoli decided it was time for a change. Get rid of the four-door 10-second machine, he thought, and replace it with a (hopefully lighter) 2-door. So out of the famous car (see more of it as it was at " A Perfect 10 " ) came that awesome drivetrain. (The development of the two-door is progressing.) But what engine to put back into the four-door?
Well, why not just slot in the factory twin turbo engine?
The words were barely out of Dominic's mouth when the deed was done. Well, not quite, but the pace at which these blokes work has to be seen to be believed. Out of the Legacy halfcut and into the WRX went the engine, crossmember (it has a hump to clear the extra exhaust) and importantly, the entire wiring loom, dash and switchgear. The latter's vital because there are some major discrepancies between the Rex and the TT Legacy in terms of plugs and sockets and their functions. It sure wouldn't be wise to try to match the new loom to the old dash, for example. Backing the TT engine was a 4-speed auto, and this also went into the car, complete with its own control computer. (Again, don't try to remove the auto ECU loom from the rest - better if you fit a manual trans just to leave all the excess wires tucked out of the way.) The driveshafts of the new combo were identical to the WRX, while the brakes from the Legacy half-cut could have been used if they weren't already the same as the Rex's.
The guys reiterate that the major headaches in the conversion are electrical, but since they've found an auto sparky who has now done a few of these conversions, even that's been sorted out. Other problems? There aren't any! And when you look at the twin turbo engine nestling in the bay you can see that many of the normal problems associated with engine transplant simply don't exist.
Cost? Well, with a twin turbo halfcut around $3000 (although this will vary) and with about $2000 for the labour of the conversion (including the electrical work) you're looking at an all-up cost of about five grand.
On the Road
So what's the car like on the road? Well, not quite what we expected. That's certainly not to say that it's bad, just that some of the engine traits take a bit of getting used to. First up, the Subaru approach to twin turbos is not at all like, say, the Nissan approach used on the GT-R. The Soobie technique is to sequence the same-size puffers, with one doing the work down low and the other chiming in up high. That's fine, but then you also have an intelligent auto trans in there with what feels to be a pretty high stall converter - and its thinking and gear-changing behaviour has a lot to do with how the car drives. Add in the fact that the WRX weights at least 200kg less than the donor car, and the whole boost system feels at times like it needs further sorting.
But maybe that's just us being picky.
The immediate driving impression is of the alacrity with which the car moves away from a standstill. Like a big-engined naturally aspirated car, the first few metres of movement can be accompanied by the jerked-back-heads syndrome - and you think wowie! But then you put your foot down harder and wait for the hell-we-have-to-hold-on wave of torque, which doesn't quite happen. Instead, the TT WRX accelerates moderately well - but slower than a standard WRX. Like, it's responsive but not shove-you-back-in-your seat stuff. Around four grand performance dies a little, then in first gear the same moderate acceleration continues on to the redline. But just wait for the autobox to change into second!
The revs drop back to 5000, and then you really do hafta hold on!
In second gear, with the two turbos loaded up and the converter doing its torque multiplication bit, the acceleration is phenomenal. You're shoved back into your seat by grunt that matches an STi - and the change to third gear just keeps her winding out in a similar exhilarating way.
So what's actually going on here? Our guess is that the factory system has been very finely optimised for the extra mass of the Legacy, where the harder-working turbos will spool up to full boost pressure more evenly. Certainly, while tests of the TT Legacy talk about a good top-end, the transition from bottom to top-end performance is never described as being as startling as this!
The AC22-measured performance figures tell the story. As with all WRXs that we've tested, performance figures varied majorly with the temp of the top mount intercooler, but after a short off-boost drive to bring down those temps, the TT WRX could sprint to 100 in about 7.5 seconds. Sure - respectable. But its rolling 60-90 km/h time really gives an indication of its performance potential - this split was just 1.7 seconds! The latter time was done with the engine above 5000 rpm - and so with both turbos a'pumping.
The theory that the WRX's mass is the upsetting factor in the way that the turbos' boost transition occurs can be supported by two pieces of evidence: as Dominic Rigoli says, "the car goes better with more people in it!"; and when climbing a steep hill, the response was a lot more linear. Interesting - maybe some tweaking of that control box full of solenoids and vacuum hoses could smooth things out?
Away from full acceleration the car is pleasant - noticeably more torquey than a standard (manual trans, at least) WRX, with the intelligent auto happy to drop back a gear at part throttle as needed. The car also drifts along on tiny throttle openings, resulting in exceptional open-road fuel consumption. The 'big engine in small car' feel at light throttle is relaxing - even seductive - and the relatively short 36 km/h per 1000 rpm fourth gearing of this car helps give a quickness of response.
In fact, in normal use the car is nicer under 5000 rpm - below those revs you avoid an unpleasant aural threshiness and always know that a certain amount of throttle movement will give just this much extra torque.
But then again, keeping the revs down there also means that you never get to experience a top end where you just hold on and aim the car in the direction you want the missile to take!
Conclusion
A viable alternative to the traditional methods of boosting WRX performance? Definitely!
Contact:
Tony Rigoli Performance (Gold Coast) 07 5528 4666
At the time of writing, the car is for sale for $19,000.
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