The Impreza WRX STI is no longer an Impreza. Subaru UK dropped the prefix three years ago in an effort to distance the turbocharged 4x4 from the more ordinary Impreza hatches it was trying to sell at the time.

The passage of those three years hasn’t, however, made the idea of an Impreza STI that isn’t an Impreza at all seem any less strange to us. Subaru stops short of calling this a ground-up new car, but there’s not a lot that has been left untouched.

Nic Cackett

Nic Cackett

Road tester
The engine's boxer configuration makes it hard to get a good response from a single turbocharger

The new bodyshell is wider, lower, longer of wheelbase and 140 percent stiffer than that of the last STI saloon, giving notable improvements in ride and handling, they say. The bodywork, too, is all new, and to our eyes it’s a marked improvement on the bland amorphousness that went before.

The suspension has been modified rather than replaced. Stiffer cross-members and bushings feature front and rear, as well as thicker anti-roll bars and slightly altered mounting points that increase toe-in at the back and ground contact under load at the front. The hydraulic power steering has also been replaced, with a stiffer column and quicker gearing fitted.

The engine and drivetrain remain largely unaltered. That means you get 2.5 litres of burbling flat four driving all four wheels via a six-speed manual gearbox (with a shorter throw and new scissor springs and detent profiles) and through a viscous limited-slip centre differential with driver-selectable front or rear bias.

The ‘EJ257’ 2.5-litre flat four gets a revised ECU, a bigger intercooler and exhaust gas recirculation for this new STI, helping it to pass Euro 6 emissions tests. The engine is mounted low in a boxer configuration, so it gives the car a low roll axis, but the layout also causes some problems.

There’s no direct injection or variable-geometry turbo technology here. Neither has Subaru found a way to shorten the inlet tracts between the cylinder heads and centrally mounted turbocharger, which would help engine response.

Subaru also runs up against a packaging problem that forces it to run oversquare cylinders in a big-capacity engine. A slightly undersquare, longer-stroke design (such as most of the rest of the industry use for better low-end torque) would force the cylinder heads even further from the turbo and might not even fit between the suspension turrets.

Porsche’s answer to all this, for the 996 Turbo, was parallel twin turbos and intercoolers, but that might not be an answer cheap enough for a sub-£30,000 Subaru.

Peak outputs are 296bhp at 6000rpm and 300lb ft at 4000rpm, which is plenty for your money. Years ago, however, those outputs would have been enough to create clear air between this car and the chasing hot hatch pack. These days many two-wheel drive variants are approaching and surpassing this mark, you only have to look at the latest versions of the Volkswagen Golf GTI, Hyundai i30N, Seat Leon Cupra 300 and Honda Civic Type R to see how far the segment has come. Let alone consider the four-wheel-drive cars that the WRX STI would line up against, with the new Audi RS3 approaching the 400bhp mark.

Subaru could certainly have done more to give this car something akin to the superior position it used to occupy on outright grunt. We’ll have to see if the car can distinguish itself by other means.

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