Vauxhall Insignia BiTurbo
Number one in the B segment, Vauxhall has increased the appeal of diesel Insignia models by introducing its most powerful diesel ever, the 2.0-litre BiTurbo with prices starting at £27,180.

Available in five-door hatch or Sports Tourer estate models, this new engine is designed to rival models from Audi and BMW. Can it compete? We took one down the Route Napoléon to find out.

Based on the existing 2.0-litre CDTi unit, there are now two turbochargers that work in sequence. At the start, the smaller turbo works by spinning up quickly at lower revs to eliminate 'lag'. This means there's 350Nm of torque available from as little as 1500rpm.

Vauxhall Insignia BiTurbo
In the mid-range, both turbochargers work together, with a bypass valve working so that gases can flow from the smaller to larger turbos, equalling maximum torque of 400Nm between 1750 and 2500rpm. Over 3,000rpm, all gases are sent to the larger turbo, meaning performance is kept up at higher speeds.

The manual version of the BiTurbo is fitted with stop-start, which makes it cleaner than the standard diesel engine it is based on. With the twin-turbo emitting 129g/km versus the standard single-turbos 134g/km. Surprisingly, it drinks less heavy fuel too, with economy increasing from 55.4mpg to 57.6mpg.

To make the most of the extra power, Vauxhall have fitted the clever FlexRide adaptive damping as standard, which is usually a £790 option on front-wheel drive Insignias. It works by reacting to driver inputs, in just milliseconds and can learn and adapt to how the car is being driven.

Vauxhall Insignia BiTurbo
Go for a four-wheel drive version and you can opt for the even more focused £1,695 SuperSports package. As fitted to all the test cars we drove, it includes high-performance Brembo brakes, the HiPerStrut front suspension that's also fitted to the 325PS Insignia VXR, VXR chassis tuning and 20-inch alloy wheels.

Other new tech features fitted to the Insignia BiTurbo includes, the latest version of the front camera system, that now features traffic sign recognition and lane departure system. There's also Adaptive Cruise control, which works by maintaining a set distance from the car in front.

So we've heard about the technology, but what's the Insignia BiTurbo like to drive? Well the lack of 'lag' means this engine is noticeably more responsive lower down the rev range, but despite the fitment of the two turbos, it is no smoother than the standard 2.0CDTi engine on which it is based. In fact, it is a bit of chugger when compared to rival Audi and BMW diesel engines.

There's no doubt it is a responsive engine, with acceleration to 60mph for the four-wheel drive manual version we drove equalling 8.4 seconds and the top speed is 142mph.

With the Supersports package, the Insignia BiTurbo 4x4 is a capable handler. There's plenty of grip, strong brakes, virtually no body roll and the ride is comfortable despite the 20-inch alloy wheels.

So would we be buy an Insignia BiTurbo? Well, this is an impressive engine, but it is a no. Despite the great performance/economy mix, it is priced too close to the new BMW 320d. The new baby BMW saloon which we drove recently is faster, more frugal, fun to drive and as such is the car we'd choose.