Review of the new Subaru Impreza STI CS400

It looked like Mitsubishi had finally claimed victory in the age-old struggle between the world's two favourite four-wheel-drive rally replicas. Its Lancer Evolution X had risen to previously unimagined levels of technology, performance and price while its arch-foe, the Subaru Impreza STi, had morphed into a hatchback and appeared to be waving a white flag. These two have never been away from each other's throats for long though, and it now looks like normal hostilities have been resumed thanks to the Impreza STi CS400.

While Mitsubishi was basking in the plaudits and polishing the awards that kept coming the way of its tenth generation Lancer Evolution, Subaru was talking to those nice people at Cosworth. The very same British engineering firm that has been at the forefront of world motorsport for over half a century, supplying components to Formula 1 and World Rally Championships teams, while also taking time out to develop a few classic performance road cars for its one-time owners Ford. Subaru asked Cosworth to help put it back in the game at the top end of the performance car market and the Impreza STi CS400 is the result.

A standard Subaru Impreza STi has just under 300bhp, while the limited run 330S version added a further 30bhp to that. This Impreza STI CS400, or 'Impreza Cosworth' as it's increasingly being referred to, is a different proposition altogether. It has 395bhp from the same 2.5-litre turbocharged boxer engine. Actually, the engine is only 'the same' in the loosest sense. Cosworth has breathed its magic on the all-aluminium flat-four powerplant with high performance pistons, con-rods, bearings and head gaskets plus a high pressure oil-pump and a completely different turbocharging system. As a result the peak power is generated lower in the rev range and torque is increased to 542Nm.

"The car should give a big shot in the arm to Subaru's profile"

Deploying all that urge effectively is quite a challenge and the Impreza Cosworth goes about it with the six-speed manual gearbox and all-wheel-drive transmission from the standard Impreza STi. Power is split 50/50 between the front and rear wheels with limited slip differentials on both axles to help maintain traction. It all contributes towards the Impreza Cosworth's stunning 3.7s time for the 0-62mph sprint and 12.75s effort for the quarter mile. It's unlikely to be a coincidence that Mitsubishi's flagship Lancer Evo X, the mighty FQ-400, takes 3.8s to complete the 0-62mph trial.

Cosworth hasn't restricted its efforts to the Impreza's engine bay. The Impreza STi CS400 rides on specially tuned suspension with Eibach coil springs and Bilstein dampers that lower the car by 15mm at the front end. The track is also wider. The aim was to improve ride quality while reducing pitch and roll during fast driving but the changes serve to add yet more aggression to the Impreza's looks as well. A braking system commissioned by Cosworth from AP Racing does the all-important stopping duties with six-pot callipers and vast 355mm front discs.

It's possible to spot an Impreza Cosworth by its super-low stance alone but specially designed spoilers front and rear will also provide clues to its potency. Inside, the cabin might not be the last word in luxury or build quality but it's perfectly suited to the business of going fast. The supportive black leather seating carries the Cosworth logo which also pops up on the floor mats and outside on the brake callipers and front grille. Individual plaques are attached to each car citing its position in a production run limited to 75 vehicles.

This is the first Coswoth-developed road car since the last comedy rear spoiler was bolted to a Ford Escort Cosworth in 1996. Over the years, the Cosworth name has taken on near mythical status with UK performance car fans and the move by Subaru to get the company on board for this project, despite its longstanding relationship with Prodrive (another UK performance engineering firm), looks like a shrewd one.

Mitsubishi must have thought it had won the war between its Lancer Evolution line and the Subaru Impreza but it did so by taking the 'Evo' to a new level of performance and technical complexity. Now Subaru has followed it into similar territory with the Impreza STi CS400 but with both cars peppering the £50,000 price-point, they are up against some high class competition. Equivalently-priced alternatives to this ultimate Impreza include performance luminaries like the BMW M3, a fully-loaded Porsche Cayman S, a Lotus Evora and Audi's RS5. All are very different propositions but it illustrates the kind of company the Impreza is now keeping. If you can cope with 100bhp less, it would also, of course, be possible to save £17,000 and settle for a standard Impreza STi.

Despite an excellent reliability record, service intervals are short and spares costly for any high performance Impreza, particularly a Cosworth. Owners who return 20mpg in mixed driving conditions must have the restraint of a monk and regardless of their religious denomination, the person at the wheel will be lucky to squeeze 250 miles out of a full tank.

Under normal circumstances, there'd be nothing new or particularly surprising about a special edition Subaru Impreza boasting more power and even more extreme performance. The difference this time is that it had looked like the Impreza's longstanding tussle with the Mitsubishi Lancer Evo had calmed down. The top Evos had developed into more complex and technologically advanced performance cars, with the Subaru content to operate as a kind of super hot hatchback. The 395bhp Cosworth-developed Impreza STi CS400 reopens hostilities between the two cars by giving the Impreza range a flagship model that's the on-paper equal of the ultimate Evo.

Only 75 Impreza STi CS400 models will be made and the £50,000 asking price will be a sticking point for many would-be buyers. The car should give a big shot in the arm to Subaru's profile and fans will be delighted to see both the Impreza/Evo battle rejoined and the famous Cosworth name back on a production model.

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