In the usual run of things we need only one reason to review a car, but in this case we have two. To begin with, this is the first Astra we've driven since Vauxhall the hatchback and Sports Tourer estate ranges were given a facelift involving new bumpers and a rearrangement of the exterior chrome, though that's not particularly relevant to the BiTurbo since it has a few styling features of its own, some of them shared with the GTC coupé.More excitingly, the BiTurbo also has a modified version of the familiar two-litre CDTi turbo diesel engine which, as the name suggests, uses two turbochargers. These are of different sizes, and the main reason for that is to extend their combined operating ability across as much of the rev range as possible. An added benefit is that they raise the engine's maximum output from 158bhp to 192bhp.That makes this the most powerful diesel engine Vauxhall has ever put into production, which it did earlier this year by introducing it to the Insignia. It follows that the BiTurbo is also the most powerful diesel Astra yet devised, and in fact it has the second highest output in the range behind the VXR.With a top speed of 141mph, a 0-60mph time of 7.8 seconds and more low-down grunt than either of those figures can suggest, it's pretty quick, and it performs well on the EU test cycle with 55.4mpg combined economy (though you'd be hard-pressed to achieve that in real life) and 134g/km CO2 emissions.Less powerful diesel Astras can do better than that, but the BiTurbo trumps the 1.6-litre petrol version, which is much slower though, in fairness, quite a bit cheaper to buy.Vauxhall diesel engines of the current era are above-averagely noisy, and even though the BiTurbo is fitted with the excellent FlexRide system, which offers three distinctly but not extravagantly different levels of suspension damping, the ride is always on the firm side. Neither of these aspects will appeal to anyone who wants a relaxing car, but sporty drivers may a) not be bothered or b) quite like them.In the Insignia, the 192bhp engine is available in different trim levels, and in the Astra GTC it's offered as an SRi, but in the hatchback line-up BiTurbo is a trim level distinct from all the others. The specification includes 18" wheels, the exterior styling changes hinted at in the first paragraph, twin exhaust tailpipes, black and red seat upholstery, a flat-bottomed leather-trimmed steering wheel and alloy pedals.All this also applies to the Sports Tourer BiTurbo, which is £1015 more expensive at £25,110. The less practical but sharper-looking GTC with the same engine costs £23,925, for which you get a 6mm lower ride height, Bluetooth connectivity and DAB digital radio as standard. Engine 1956cc, 4 cylinders Power 192bhp Transmission 6-speed manual Fuel/CO2 55.4mpg / 134g/km Acceleration 0-60mph: 7.8 seconds Top speed 141mph Price £24,095 Details correct at publication date