The 2014 Alpina D3 Bi-turbo is a key car for the small Bavarian manufacturer because it replaces the 3 Series-based model that really put the company on the map.
Offered as a coupe, estate and saloon, the original D3 used a twin-turbo four-cylinder diesel engine, retuned and mated to Alpina's own exhaust system so it produced plenty of power while still offering decent fuel economy and CO2 emissions. The new version, which is now available as a saloon and estate, has to match those characteristics.
It's perhaps surprising, then, to discover that instead of a 2.0-litre four-cylinder unit, the new D3 gets a twin-turbo 3.0-litre straight six engine. Pace is unlikely to be an issue, but Alpina's engineers obviously feel they can get the bigger engine to sip fuel. They're clearly confident that the overall package has improved, too, because they've also whacked more than £13k onto the price; the original D3 slotted in at around £33,000, whereas this one starts at £46,950.
The retuned BMW engine produces 345bhp at 4000rpm, and a frankly astonishing 516lb ft of torque between 1500rpm and 3000rpm. Even when it's transmitted through a remapped version of BMW's eight-speed automatic gearbox, that potency is enough to catapult the D3 saloon from 0-62mph in 4.6sec, and on to a top speed of 173mph. Alpina claims this makes the D3 the fastest diesel saloon in the world.
The fuel economy? Alpina's official figures say 53.3mpg combined, with CO2 emissions of just 139g/km. There aren't many vehicles with such an impressive blend of pace and economy, then - but does the driving experience back up the numbers?
What's the 2014 Alpina D3 Bi-turbo like to drive?
It won't surprise you to hear that the D3 Bi-turbo is jaw-droppingly quick by any standard, let alone for a diesel saloon. It's fast enough away from rest, but the in-gear acceleration from around 40mph requires constant monitoring, just to ensure that you haven't blitzed every speed limit in the land.
As with all Alpinas, the eight-speed automatic gearbox is controlled using buttons behind the steering wheel (we'd prefer paddles). Still, it's quick enough to react when you leave it to its own devices and if it's in manual mode, you can have an involving drive – although you are soon aware that, with this much torque, you really don't need to change gear much.
However, the engine note is barely any more appealing than the diesel rattle of the old D3's four-cylinder unit. It's not particularly characterful – just a sort of gravelly grumble that never goes away (Alpina's exhaust tuning probably has something to do with that). So if you're expecting the switch to six cylinders to bring a paradigm shift in smoothness, you will be disappointed.
The wall of torque can occasionally overwhelm the rear wheels on a damp road, but the D3's balance and accurate steering mean you're never likely to feel it's getting away from you. As is often the case with Alpinas, the ride quality is better than it has any right to be, given that the smallest wheel size available on the D3 is 19in, and our test car was riding on 20s. The fact that Alpina doesn't fit run-flat tyres plays a part in this, although there's no doubt the company has a good handle on suspension set-ups, too.
What's the 2014 Alpina D3 Bi-turbo like inside?
You won't find much novelty inside the D3 if you're familiar with the cabin of a BMW 3 Series. There are a few different finishes, true, and Alpina's blue speedometer and rev counter are present as always - but that aside, you could be sitting in any high-end 3 Series. It's worth remembering, though, that Alpina does offer a bespoke cabin trim service; should you want your car's roof lined in lime green felt, it can happen.
It's time for Alpina to rethink its internal badging policy, though. The individually numbered plaque used to be mounted in the roof lining, just above the rear-view mirror - and while it wasn't exactly pretty, at least that positioning kept it out of your regular line of sight. These days it's given greater prominence, plonked as it is at the bottom of the centre console – and it looks plain tacky.
Should I buy one?
As a standalone product, the Alpina D3 Bi-turbo is a towering achievement, offering supercar performance with the potential for than 40mpg in real-world driving. It's also comfortable, classy transport for four people who really want to get somewhere in a hurry.
On the other hand, it does feel a very different proposition from the four-cylinder car, to the point where we we're not sure it will appeal to the customers the original D3 brought in.
We don't doubt that Alpina's boffins could have produced a slightly slower but even cleaner D3 if they'd stuck to a 2.0-litre engine. The switch to six cylinders has produced a hike in performance, sure, but it has created a car of different character and, at this price, one that is going to appeal to a different customer. It's still a bargain, but a slightly more exclusive one.
What Car? says...
Alpina D3 Bi-Turbo saloon
Engine size 3.0-litre turbo petrol
Price from £46,950
Torque 516lb ft
0-62mph 4.6 seconds
Top speed 173mph
Fuel economy 53.5mpg