Subaru has revealed official photos and complete technical specs as well as pricing for the Cosworth Impreza STI CS400.
Equipped with a tuned 2.5-litre turbocharged boxer engine that packs 33 percent more power, the Cosworth Impreza STI CS400 delivers 400 horses and 542 Nm of torque which get sent to all  four wheels via a 6-speed manual transmission. The Cosworth Impreza STI CS400 takes only 3.7 seconds when accelerating from nought to 62 mph and reaches an electronically limited top speed of 155 mph.
Besides the new turbocharger system the engine powering the Cosworth Impreza STI CS400 received twin overhead camshafts per cylinder bank (DOHC), an Active Valve
Control System (AVCS), high-performance pistons, heavy duty cylinder head studs,
high-performance multi layered head gaskets and a higher-pressure oil
The Cosworth Impreza STI CS400 has also received performance brakes, a tuned suspension, a new exhaust system and Recaro front seats.
The Cosworth Impreza STI CS400 price starts at 49,995 GBP and production will limited to only 75 units.
Subaru press release :
The new Cosworth Impreza STI CS400 is the result of one of the most
eagerly anticipated automotive collaborations in recent times.  The
first genuine Cosworth-developed road car since 1996, the latest limited
edition Impreza offers performance-car fans the thrill of a lifetime
combined with exclusivity – production will be restricted to 75 cars.
The Cosworth-tuned, turbocharged vehicle is one of the world’s most
accelerative hatchbacks.  The renowned 2.5-litre turbocharged ‘Boxer’
engine is transformed to produce 33 per cent more power, drawing heavily
on Cosworth’s extensive Formula 1 experience.  The engine, which drives
all four wheels via a six-speed manual gearbox, boasts an impressive
400 ps and the new model reaches 62 mph in just 3.7 seconds, going on to
cover a quarter mile in 12.75 seconds at a terminal speed of 107 mph. 
Top speed is limited to 155mph.
The Cosworth Impreza STI CS400 features an extensive range of
Cosworth-engineered components in the engine, turbo system, exhaust,
suspension, brakes and wheels, plus subtle improvements to the exterior
and interior styling to create a truly distinctive high performance car
with everyday hatchback practicality.
Marketed exclusively in the UK in right-hand drive form, the Cosworth
Impreza STI CS400 is available in a choice of three exterior colours
(Spark Silver, Dark Grey and San Remo Red), and is priced from £49,995
Engine delivers a 33 per cent power hike
At the heart of the new Cosworth Impreza is a heavily revised version
of the marque’s famous horizontally-opposed, all-aluminium Boxer
engine.  The ‘flat-four’ power unit is removed from the car, hand
finished, and several internal and ancillary components are replaced
with up-rated items, specified by Cosworth.
As with all Impreza ‘Boxer’ engines, the STI Cosworth unit features
twin overhead camshafts per cylinder bank (DOHC) plus an Active Valve
Control System (AVCS) to deliver variable valve timing and enhance
low-speed pulling power.
The focus of the Cosworth engine upgrade was to keep the enhancements
simple, efficient and as close as possible to the original equipment
design to guarantee reliability and easy maintenance at regular Subaru
Internal upgrades include high-performance pistons, which are
manufactured using the same methods as those employed to create
Cosworth’s Formula 1 pistons.  Special features reduce carbon build-up,
minimise friction and reduce weight.
Forged connecting rods are made from high-strength 4340 (EN24) steel
and the special Cosworth engine bearings boast a unique combination of
design, metallurgy and engineering.  Heavy duty cylinder head studs,
high-performance multi layered head gaskets and a higher-pressure oil
pump are also fitted. 
The overall result is a huge increase in torque higher up the rev
range, and significantly improved in-gear acceleration.  This not only
makes the Impreza more tractable for day-to-day road use, but also a far
sharper tool on the race track.
New turbocharger and ‘breathe easy’ exhaust systems
An all-new Cosworth turbocharging system features a new compressor
design and wastegate actuator to supply up-rated boost pressure and
deliver increased power.
A unique exhaust system was developed to allow the engine to
‘breathe’ more easily and unleash its full potential.  Larger capacity
tubular manifolds and increased diameter downpipes speed up the
evacuation of hot gases.  The first catalyst is a non-restrictive design
and larger tail pipes give the exhaust note a unique tone.
After the in-depth Cosworth performance upgrade which includes an ECU
re-map, the boxer engine in the CS400 generates 33 per cent more power
(400 ps at 5,750 rpm, compared with 300 ps at 6,000 rpm for the standard
Impreza WRX STI), and 542 Nm of torque, while remaining within the
torque capacity design limits of the original Impreza drivetrain.
Manual transmission and All-Wheel Drive system
To handle the increased power of the Cosworth-tuned engine, the
Impreza STI’s six-speed manual transmission has carbon synchromesh
applied to the top three ratios and a short throw linkage for quicker
There is also an upgraded single-plate clutch with a revised pressure
plate, bearing and disc.  The gearbox and final drive ratios are
The Cosworth Impreza’s full-time All-Wheel-Drive transmission with
front and rear limited-slip differentials, features a 50/50 front to
rear torque split as the default, however, the torque split is varied
electronically according to changing conditions.  The multi-mode Driver
Control centre differential with viscous coupling senses which axle has
the better grip and varies the split ratio in milliseconds to distribute
torque accordingly, thus maximising traction and minimising the
possibility of wheelspin.
Fine-tuned suspension
Improving the Cosworth Impreza’s handling, steering feel and driver
feedback – without compromising ride comfort – was a primary target for
the development team.
Retaining Subaru’s original suspension layout and major components,
Cosworth and a team of chassis engineers collaborated with Bilstein and
Eibach technicians to tailor a ride/handling/steering package that was
ideally matched to the new model’s increased performance.
Special Eibach coil springs and new Bilstein inserts, featuring
unique damping characteristics, were manufactured to Cosworth’s
specifications.  The ride height was lowered by 10 mm at the front. 
The benefits of this fettling are twofold. Firstly, there is a big
improvement in ride quality generally, making the Impreza easier to live
with on a day-to-day basis.  Secondly, its on-the-limit behaviour is
more focused and composed.  The damping upgrades mean that there is less
pitch and roll when turning into corners, meaning that keen drivers can
get back on the power earlier and make the most of the car’s
Symmetrical All-Wheel-Drive system.
Upgraded ‘racing’ brakes enhance stopping power
To match the new Impreza Cosworth’s supercar pace, Cosworth
commissioned AP Racing to develop more powerful front brakes.  Larger
diameter (355 mm) ventilated front discs were adopted, with
motorsport-style six-pot callipers featuring bespoke pistons operating
on larger brake pads.
The difference in performance is immediately noticeable.  The harder
pads help to minimise fade, meaning that drivers can count on the AP
stoppers for effective retardation time and time again.
The standard Impreza WRX STI’s rear brake discs, overall brake
balance and original ABS system have been retained.
‘Stand-out’ looks, plus new style wheels
The outstanding performance of the Cosworth Impreza is reflected in
its ‘stand-out’ appearance and standard Xenon headlamps.  The lowered
ride height and wider track give the car a whole new stance which is
reinforced by a new shape front bumper, new fog lights, upper and lower
mesh grilles and a new rear spoiler.
Discreet Cosworth badging is carried on the lower grille, front
seats, brake callipers and floor mats.  Individually numbered plaques
are fitted on the engine and door sills.  Each Cosworth Impreza STI
CS400 is supplied with a numbered certificate of authenticity.
Although the new model’s alloy wheels are a similar overall size to
those of the regular Impreza WRX STI model – 18 x 8.5 inch – they are
lighter and stronger.  Called ‘Pro Race’ and finished in anthracite the
latest wheels from the Team Dynamics range were selected as compatible
with the Subaru’s five-stud design.  These wheels have a 43 mm offset
(the standard STI wheel’s offset is 55 mm) and extend the track by 12 mm
– improving handling and filling the car’s wheel arches more
effectively for a more aggressive stance.
The new wheels are fitted with high performance, low profile Michelin
SP3 tyres chosen for their dry- and wet-road grip, durability, and low
noise levels.  Tyre size is 245/40 R18 and the tread pattern is
Interior modifications and generous premium equipment
Inside, the sporty new Recaro front seats, the rear seats and
steering wheel are all re-trimmed in Cosworth-branded black leather. 
Also distinguishing the CS400 are Piano Black centre stack and trim
accents, and the fitment of privacy glass.
Standard features carried-over from the WRX STI model include: LED
(light-emitting diode) tail lamps, front and rear electric windows,
10-speaker, six-disc radio/CD player, satellite navigation, Smart-entry
and push-button start, plus front, side and curtain airbags.  
Full ownership benefits
The new Cosworth Impreza STI CS400 comes with the reassurance of a
three-year or 36,000-mile warranty, plus 12-year anti-corrosion cover
and three-year paintwork warranty.
This is in addition to three years’ membership of Subaru Assistance –
a comprehensive home and roadside repair and recovery package
throughout the UK and Europe administered by Mondial Assistance. 
New Cosworth Impreza STI CS400
Body and Chassis
Five-door, five-seat hatchback, with all-steel unitary construction
body shell.  Longitudinally-mounted petrol boxer engines driving the
front and rear wheels (AWD) via a six-speed manual transmission. 

SEE ALSO:  Subaru Forester STI Sport Edition is Japan-only
STI 2.5-litre / 400 PS   
Name                          Subaru Boxer
Type                            DOHC, horizontally opposed ‘flat four’
Capacity                      2.5-litres, 2457 cc
Bore & Stroke                         99.5 x 79.0 mm
Compression ratio      8.2:1
Max power                   400 PS (295 kW) @ 5,750 rpm
Max torque                  542 Nm (400 lb.ft) @ 3,950 rpm
Valves                         16 (4-per-cylinder) with Dual AVCS
Fuel system                Multi-point injection
Construction               Aluminium cylinder block and heads
Emissions class         Euro Stage 5
Manual Six-speed
Gear Ratios  
1 3.636:1
3 1.590:1
6 0.707:1
Reverse    3.545:1
Final Drive (rear)  3.900:1
SEE ALSO:  Rich Hammond buys the Subaru Impreza from A Scandi Flick

Full-time all-wheel drive with centre differential and viscous
coupling, plus Vehicle Dynamics Control, Rear limited-slip differential,
Front limited-slip differential and Si-Drive adjustable centre

Suspension & Damping  
Front Fully independent subframe-mounted MacPherson Struts, with Eibach
coil springs and gas-filled Bilstein shock absorbers. Anti-roll
stabiliser bar 
Rear Fully independent subframe-mounted Multi-Link, Eibach coil springs
and Bilstein gas-filled shock absorbers (adjustable) anti-roll bar 


Type                            Electric power-assisted rack & pinion
Gearing                       2.5 turns lock-to-lock
Turning circle (m)       11.0
Front                           355 x 32 mm ventilated discs with 6-pot callipers
Rear                            316 x 20 mm vented discs with single-pot callipers 
ABS                             Four-Channel anti-lock system with EBD
Wheels & Tyres  
Alloy 18 x 8.5 inch, with 245 / 40 R18 directional tyres  
Dimensions (mm)  
Overall length              4,415
Overall width               1,795*
Overall height              1,475
Wheelbase                  2,625
Front track                   1,530
Rear track                   1,540
Ground clearance           140
*excluding door mirrors  
SEE ALSO:  Prodrive P25 is an Impreza rally car reborn
Interior (all models)    
  Front Rear
Headroom 1,024               951
Legroom                                    1,091 960
Shoulder room 1,430               1,426
Hip room                                   1,384 1,370
Capacities  (all
Fuel tank   60 litres  
Luggage (VDA)   301 litres rear seats up
  1,216 litres   rear seats down
Weights (kg)     
Curb weight (min.)      1,505   
Gross weight               1,980  
Top speed / mph 155 (electronically limited  
0-to-62 mph / sec 3.7  
Fuel Economy (mpg)    
Combined cycle          [tbc]  
CO2 g/km                   [tbc]  
Source: Subaru