The sole engine providing Subaru WRX STI performance is a 2.5-litre turbocharged petrol using four horizontally opposed cylinders.
Developing 296bhp and 407Nm of toque at 4,200rpm, the power delivery of this engine is a long way from the linear, refined race to the redline its rivals enjoy. There's no direct fuel injection or high-tech turbocharging here to help driveability or fuel economy, so what you're left with is not a huge amount of go until around 3,500rpm. At that point the turbo wakes up and all hell breaks loose, slinging you down the road to the tune of the whistles and wooshes associated with turbocharged cars.
Subaru claims a 0-62mph time of 5.2 seconds for the STI, its top speed 159mph. We've got absolutely no reason to disbelieve either stat - this feels like a seriously fast car that takes off from a standstill like a rocket thanks to its four-wheel drive system.
It has to be said, its power delivery is far more theatrical than its rivals too. The delicious wait for all that power at once truly is something to be relished.
You can adjust the engine's throttle response using Subaru's S Mode system. In ‘I' mode the car decides what's best for top fuel economy and smooth driving. Sport (or S) mode sharpens up the engine's response, while S# (Sport Sharp) mode is the ultimate in pin-sharp throttle control.
While the reason for using such an engine configuration is predominantly handling, there's a very distinctive sound from the exhaust. Best described as a ‘burble', it's lower-pitched and has more of a rumble than most four-cylinder engines out there.
Your only gearbox option is a six-speed manual that Subaru claims to have modified heavily to make the car better to drive than the previous version. We found both throw length and placement to be brilliant, but there was a slightly notchy feeling when swapping ratios that took a bit of getting used to. It's nothing to worry about, though - it's a characteristic of STI cars.
Here's where the WRX STI really comes into its own. The car's handling - on the road at least - is nothing short of excellent. There's more grip on offer than you can reasonably use on most UK highways, and even when you push the boundaries you're met with a pliable and adjustable chassis that won't intimidate.
It has a clever four-wheel drive system installed and this provides huge amounts of grip in all conditions. It comes fitted with a central limited-slip differential which sends 50 percent of the engine's performance to the front, and 50 percent to the rear. You can also choose between Auto, Auto- and Auto+ modes for the differential depending upon your requirements. Auto lets it fend for itself, Auto- sends more torque to the rear of the car and improves steering response for precise handling, and Auto+ limits torque for the best performance on slippery surfaces.
Mounting the engine low in the car's structure (thanks to its horizontally opposed cylinders as mentioned before) means a lower centre of gravity, and so less tendency for the body to roll through corners.
A far more rigid (up to 140 percent more, apparently) body shell helps here too, with less flex meaning more driver input translated to actual movement of the car.
We found the brakes excellent too. The discs measure 17 inches in diameter, which is as large as many cars' alloy wheels. They're hidden by 18-inch lightweight alloys.