Subaru has at last revealed details of its hardcore new Impreza WRX STI which is substantially different to the non-turbo five-door models now being delivered to first customers.

Developed by a dedicated team of performance-loving engineers, the stunning new WRX STI debuts at the Tokyo Motor Show on 24 October, with first UK deliveries due next spring.

And with a heavily-revised new 300 PS turbocharged 2.5 litre ‘boxer’ engine, totally new platform and suspension plus even more advanced symmetrical all-wheel drive system, the World Rally Championship look-alike is sure to satisfy Subaru traditionalists.

Its proportions are radically altered compared to both the previous Impreza and mainstream new 1.5 and 2.0 litre models.

For example, the wheelbase is 95 mm longer than the old car despite overall length being 50 mm shorter. This reduces front and rear overhangs and enhances stability.

And at 1,795 mm wide, the new STI is even 55 mm wider than the new model thanks to heavily blistered wheelarches, while front and rear tracks are 45 and 40 mm greater for a ground-hugging stance.

Apart from the extended front and rear wings, key visual differences include a mesh front grille and a new, deep bumper design with sporty vertical air vents at either side to help cool the intercooler.

Immediately behind each front wheel is a vertical air outlet for the intercooler, topped by an ‘STI’ moulding plate.

Specially-designed side skirts neatly blend into the extended wheelarches, while an oversized roof spoiler with high-mounted stop lamp further distances the WRX STI from the mainstream Impreza. In addition, an integrated rear bumper diffuser reduces high-speed lift.

At the rear, four exhaust pipes twinned in pairs at either side of the body not only give a distinctive look but reduce exhaust air-flow resistance by 38 per cent, increasing power and reducing noise.

Colour choices will include Subaru’s signature ‘WR Blue’ and while gold-coloured alloy wheels are available, other designs include high-lustre silver alloys measuring 18×8.5ins with 245/40R tyres.

The new Impreza WRX STI boasts a much plusher interior than before, offering leather/Alcantara-covered sports seats as standard with Recaro seats as an option. Curtain airbags are standard and the audio system has been upgraded.

Continuing on the comfort theme, the totally new suspension combines outstanding road-holding and driver involvement with a much smoother ride for passengers thanks to the multi-link double-wishbone rear suspension.

Like the previous Impreza WRX STI, the new car has inverted front suspension struts which provide a more rigid mounting and less camber-change during hard cornering. Aluminium front suspension lower arms reduce unsprung weight.

And for an even lower centre-of-gravity for enhanced grip, the front of the engine is 22 mm lower than before with the differential centre down by 10 mm.

The braking system has been developed in conjunction with Italian specialist, Brembo, and features four-pot callipers at the front and twin-pot at the rear – both ventilated discs. The system also includes four-channel, four-sensor Anti-Lock with Electronic Brakeforce Distribution.

A multi-mode Vehicle Dynamics Control System allows the driver to select the best setting for the prevalent road conditions. For example, it can be turned off altogether or set to ‘Traction’ which delays artificial interference.

The award-winning 2.5 litre horizontally-opposed ‘boxer’ engine benefits from a thorough revision which includes a larger and more efficient intercooler which increases power.

The new STI also boasts stronger low to mid-speed torque thanks to variable-valve timing for the intake and exhaust system and a fast-warm catalytic converter for reduced emissions.

Power is now 300 PS at 6,000 rpm with torque of 300 lb ft at 4,000 rpm – increases of 19 PS and 11 lb ft respectively.

Also new is Subaru’s Si-Drive system as fitted to the Legacy 3.0R spec.B. This gives the driver three different engine-response programmes at the turn of a switch, ‘Super-Sharp’ Mode giving the ultimate in throttle response.

The much-praised six-speed manual transmission has been revised, with a shorter-throw gear-change and lighter movements, especially from neutral to 1st and 1st to 2nd gear thanks to a revised synchromesh.

As before, the symmetrical all-wheel drive system features a centre viscous-coupling plus front and rear limited-slip-differentials. This shares grip front to rear and side-to-side, constantly adjusting for maximum road-holding.

A firm favourite with existing STI owners, the Driver’s Control Centre Differential has been improved, giving even more choice of handling characteristics.

The DCCD is operated via a switch in the centre console, allowing the driver to manually select the torque distribution front to rear, reverting to automatic mode every time the ignition is switched off.

For example, he or she can choose between having a sharper cornering turn-in or more stable straight-line running.

In Manual Mode, the driver can adjust the front to rear torque distribution through varying degrees to suit different road conditions such as loose gravel or soft snow.

Now, for the new Impreza WRX STI, the DCCD switch also allows the selection of three different types of ‘Auto’ Mode.

  1. Auto Mode is selected when the engine is started and covers most road conditions.
  2. Auto+ Mode places the emphasis on traction for slippery roads, sharing out the torque more evenly between all four wheels and enhancing straight-line stability.
  3. Auto- Mode increases agility by enhancing steering response through less torque-split interference.

Lawrence Good, Subaru (UK) Limited Managing Director, said: "The new WRX STI will be the perfect addition to a new range of Imprezas which are appealing to a wider, more mainstream audience.

"With its improved ride, refinement, interior space and practicality coupled with even more power and driver involvement, not to mention the kind of road presence Imprezas are renowned for, we are convinced our loyal fans will not be disappointed."

Technical Specifications

Body Size (length/width/height) :4,415 X 1,795 X 1,475 mm
Wheel Base :2,625 mm
Track (front/rear) :1,530/1,540 mm
Kerb Weight :1,480 kg
Engine Type :Horizontally-Opposed, 4-cylinder Dual AVCS (Active valve control system) 16-Valve DOHC Intercooled twin scroll Turbo Engine
Bore/Stroke :92.0 X 75.0 mm
Displacement :1,994 cc
Max. Output :227kW(308PS)/6,400 rpm
Max. Torque :422Nm(43.0kgfm)/4,400rpm
Fuel System :EGI(Multi point sequential injection)
Fuel tank capacity :60 litre
Transmission :6MT:Forward 6-speed/Reverse 1-speed
Gear Ratios :3.636 (1st)
2,375 (2nd)
1.761 (3rd)
1.346 (4th)
1.062 (5th)
0.842 (6th)
3.545 (Reverse)
Final drive axle ratio :3.900
Suspension(front/rear) :Independent, MacPherson strut type/Double wishbone type
Tyres :245/40R18
Wheels :18" BBS light alloys in Gold or Silver