2010 Subaru Impreza STI CS400 news, pictures, and information

The first result of an exciting partnership between high performance technology supplier, Cosworth and the UK distributor of Japanese car manufacturer, Subaru has been announced.

	Vital Stats
Engine : 2.5 L., 4-cylinder Power: 395 hp Torque: 398 ft-lbs
6-speed Manual

ÚK General Manager & Director, Jog Lall:
'The Cosworth Impreza STI CS400 is a perfect example of the diverse scope of business activities that underpin Cosworth's ongoing success. We have used the full range of Cosworth's in-house engineering capabilities to produce a road-going Impreza that is capable of sports car performance, not leaving one stone unturned in the pursuit of the right solution.'

COSWORTH IMPREZA WILL HAVE SUPERCAR-HUMBLING PACE

At the heart of the new Subaru 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 wîth up-rated items, specified by Cosworth.

As wîth 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 dealerships.

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 ECÚ re-map, the boxer engine in the CS400 generates 33 per cent more power (400 ps at 5,750 rpm, compared wîth 300 ps at 6,000 rpm for the standard Subaru 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 Subaru Impreza STI's six-speed manual transmission has carbon synchromesh applied to the top three ratios and a short throw linkage for quicker shifting.

There is also an upgraded single-plate clutch wîth a revised pressure plate, bearing and disc. The gearbox and final drive ratios are unchanged.

The Subaru Cosworth Impreza's full-time All-Wheel-Drive transmission wîth 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 wîth 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 Subaru Cosworth Impreza's handling, §teering 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 wîth Bilstein and Eibach technicians to tailor a ride/handling/§teering 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 wîth 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.

Úpgraded 'racing' brakes enhance stopping power