What it has produced is a Subaru Impreza STi with a significantly upgraded engine and chassis and some pleasingly stealthy styling modifications, which is capable of cracking 62mph in just 3.7sec, and a standing quarter mile in only 12.75sec. As you’ll already know if you’ve been reading our blogs section, the latter figure is less than half a second slower than a 572bhp Audi RS6.
What’s it like?
Almost as good as you’d expect it to be, even looking back with the rosiest of specs at Cosworth’s old fast Fords. The outfit has done a very thorough job of transforming this Impreza into a rapid but useable road car, and has corrected many of the standard Impreza STi’s shortcomings in the process.
We’ll deal with the chassis and running gear first, because that’s the biggest surprise. Cosworth engineers have kept the Impreza’s major chassis mechanicals – struts up front, independent multi-linked arms at the rear – but has specced Eibach springs that allow the car to run 15mm lower on its front axle. They’ve also gone for specially tuned Bilstein dampers all round, and have changed the STi’s chassis bushings, too. They’ve chosen lightweight 18in wheels and Michelin Pilot Sport 3 tyres, as well as 355mm ventilated front brakes and six-piston calipers from stopper specialist AP.
And as a result of all that, the CS400 is an STi that is much more controlled, responsive and precise to drive, and yet it’s also suited to rutted UK tarmac. That drop in ride height has eliminated a lot of the unsettling initial body roll that standard STis suffer with; it’s also made the car’s steering a great deal more accurate and positive, although it’s still quite light.
But it’s this STi’s damping finesse that’s most remarkable. If you’re expecting a trolley-jack ride, you’ll be blown away. The car feels like it’s got suspension travel and damper control to spare 90 per cent of the time, even on really testing backroads, and those new bushings make it surprisingly quiet and smooth over sharper intrusions.
Oddly, the Cosworth Impreza doesn’t quite blow you away where you expect it to: in the engine department. That’s not for want of effort on Cosworth’s part. It has completely stripped Subaru’s aluminium 2.5-litre flat four in the process of making this engine, and fitted new pistons, bearings, con rods, gaskets, head studs, and a completely upgraded turbocharger, intake system and exhaust. Such is the company's devotion to this car’s powerplant, Cosworth has even taken the oil pump to bits to ensure that it’s working efficiently.
There are just two problems spoiling this car’s engine. One of them is turbo lag: the CS400 has what might charitably be described as ‘soft’ throttle response. Floor the accelerator, even up at 2500rpm, and it’s usually between three and four seconds before you get full boost. Blame the Impreza’s intercooler, and its necessarily long intake plenums, for that.
The second problem, predictably, is that even on full boost, you rarely feel like you’re getting the engine’s full 395bhp. Which is because you’re not, of course; 395bhp at the crank probably translates into about 340bhp at the wheels of this car – and that’s by Cosworth’s own estimation - thanks to the efficiency losses of the car’s diff-happy drivetrain. The CS400 feels fast, but no more potent than a few other wicked-strength hatches we could mention.
Should I buy one?
You may not be able to unless you’re quick. Subaru UK is offering only 75 of these cars, and they’re almost all gone. And missing out on one would be a tragedy for Impreza devotees: this is one great fast Scooby, imperfect powertrain and all.
In the cold light of day, the Impreza CS400 is a tough car to recommend to a less partisan customer. As quick as it is, a Nissan GT-R would be faster still and is within sight on price, and either a Porsche Cayman S or Lotus Evora would make a more involving drive.
Which is why it’s such a shame that Subaru UK isn’t offering twice the number of Cosworth Imprezas at half of this car’s premium - because if this were a £40k car, we’d be recommending it to all-comers.
As it is, you’ll need to be a fully paid-up member of the fast 4x4 fan club to justify a CS400. The car, we like; the price is the disappointment.
Cosworth Impreza STi CS400
Price: £49,995; Top speed: 155mph (limited); 0-62mph: 3.7sec; Economy: na; CO2: na; Engine: 4 cyls horizontally opposed, 2457cc, turbocharged, petrol; Power: 395bhp at 5750rpm; Torque: 400lb ft at 3950rpm; Gearbox: 6-spd man
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