The mere sight of this MY03 Subaru Impreza STi causes its owner, Jim, a
painful combination of excitement and frustration. It’s exciting because it’s a
nitrous-fed monster that spits out around 400kW. But it’s also a source of
immense frustration because, well, it’s as useful as an mantelpiece ornament.
You see, Jim recently lost his licence while driving his Subie. No longer can he
wind out that hi-po flat-four through the top-end; heck, he can’t even drive to
the shop for milk.
But disqualification from driving doesn’t mean abandoning your plans to
modify!
Open this STi’s aluminium bonnet and you’ll find a force fed
2-litre DOHC flat-four that puts out 195kW in factory form (which is de-tuned
from Japanese spec). The stocko motor offers strong mid-range thrust and kicks
the STi down the quarter mile in around 14 seconds flat.
But Jim’s example can now embarrass a stock STi thanks to its much improved
lung capacity. There’s a full-length APS (Air Power Systems) exhaust, APS cold
air intake with K&N filter element and a free-flow APS front-mount
air-to-air intercooler. This replaces the standard top-mount intercooler, which
is negatively affected by under-bonnet heat. The factory STi blow-off valve is
configured to recirculate air through the induction system.
The standard VF35 STi turbocharger is fine for applications up to around
250kW but it isn’t up to Jim’s ask. So the turbo was replaced by a
bolt-on APS SR40 ball-bearing turbo. The new turbo is worked to 20 psi using a
Blitz electronic boost controller.
The fuel system is beefed-up with 630cc side-feed injectors used
with the standard rails. A ‘600hp’ Bosch Motorsport fuel pump and custom surge
tank ensure the injectors never run dry. The factory ignition system remains
untouched.
Controlling fuel and ignition timing is a UniChip interceptor unit, which
receives a load input from the factory airflow meter. The airflow meter is
integrated into a new APS cast alloy housing.
With the APS SR40 turbocharger set to deliver 20 psi boost, Jim’s STi can
stomp out 212kW at all four wheels (measured on a Dyno Dynamics chassis dyno).
This is around 80 percent more than the standard ATW output, so it’s reasonable
to assume flywheel output is up to around 350kW. So far, the standard clutch and
6-speed gearbox have accepted this increased output without failure.
But we’re not so sure that record of reliability will continue...
The latest mod to Jim’s STi - which was completed just before our photo shoot
- can be found in the boot. A Nitrous Oxide Systems nitrous tank (complete with
an electric warmer) stores N20 for a fogger nozzle which is mounted near the
entry to the throttle. The nitrous is manually activated by a momentary switch
on the gear knob. Damian from G-Tech can fit a choice of nozzles to vary the
amount of extra grunt that comes from the nitrous and, at the time of writing, a
40hp (30kW) shot was given the nod.
With around 350kW at the flywheel plus a 30kW shot of nitrous it seems you’re
looking at 380kW - but Damian from G-Tech says is will be more than likely
around 400kW (around 270kW at the wheels). This is due to the bonus cooling
effect of nitrous.
Quarter mile times? Well, nobody knows for sure but you’d have to be looking
at 12s.
In all likelihood, you wouldn’t recognise this as a 12 second machine when
driving through traffic.
Jim has fitted tasty Gestalt Virouge 20 inch rims with Nitto tyres and added
gtech stickers down the side, across the bonnet and the back window. The
stickers are coloured pink to highlight the original STi badges.
The body is lowered several inches but the standard STi
dampers remain in operation, as do the Brembo brakes.
Inside, you’ll find the factory STi wrap-around seats and all the sporty
bits. Jim has also added a set of three STi Defi gauges in a beautifully
integrated centre gauge pod. There are gauges for oil and water temperature, oil
pressure and a separate boost gauge can be seen on the steering column. Oh, and
there’s no need for a shift light when the factory already gives you one. Jim
says a television screen will soon be making its way onto the scene.
When Jim finally gets his licence back you can bet he will follow through on
his plans to upgrade the engine internals and fit a bigger turbo – while also
maintaining the car for Monday to Friday use. His weekend ride, if you must
know, is a 2005 Yamaha R1 with aftermarket pipes and an upgrade ECU – a proven
10.4 second thrill machine!
Update:As this article goes
online, Jim has had his licence reinstated and the STi has been further modified
to deliver 320kW at the wheels. A 2.5 litre engine is next on the agenda - and
the goal is now around 380kW at the treads!
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