Frankfurt motor show - German tuning house Alpina, known for its polished upgrades of key BMW models, has brought this gem to the 2013 show - the D3 Biturbo, based on the current 3 Series Touring and its proven straight-six three-litre turbodiesel engine.
Alpina's whitecoats have smoothed out the intake paths from the air intake to the air-filter body and fitted a bigger intercooler with revised air-flow plumbing to help the big six breathe in.
Then, to help it breathe out, they designed a special exhaust manifold, made from a highly heat-resistant alloy called D5S (don't ask us what's in it; if we told you we'd have to kill you) that allows them to run the two-stage turbocharger a scorching 50 degrees hotter than BMW recommends.
Additional radiators in front of the wheel arches, one of which is an oil/water heat exchanger, help the engine to keep its cool under a lot more stress than BMW had in mind when they built it.
And finally, they asked the motorcycle boffins at Akrapovic to build them a free-flowing stainless-steel exhaust system that would meet EU6 emissions standards without making the car sound like a compression-ignition food blender.
All of which has allowed Alpina to screw down the wastegates and remap the common-rail fuel-injection controller to the tune of 257kW at 4000 revs and 700Nm from 1500 to 3000rpm - that's a whopping 67kW and 140Nm more than BMW quotes for the standard-issue 330d.
Alpina quotes a 0-100km/h sprint time of 4.6 seconds and a top speed of 278km/h; combined-cycle fuel consumption, however, is increased by 8.2 percent, from 4.9 to 5.3 litres per 100km.
All that grunt reaches the road through an eight-speed ZF auto transmission built specially for Alpina, with three modes - Auto, Sport and Manual - offering relaxed cruising, sharp shifting at peak revs and total manual control via shift buttons on the back of the steering wheel respectively.
When in Manual mode, the driver can also select Sport+ or DSC Off, which prevents the transmission from overruling you and changing up just when you don't want it to, such as in the middle of a tight uphill corner on your favourite twisty road.
BMW's Eco Pro function, which reduces fuel consumption with more defensive throttle and transmission mappings, as well as Efficient Dynamics systems such as idle stop, is retained as issued.
The D3 Bi-Turbo Touring comes with electronically adjustable dampers, tuned springs and stiffer anti-roll bars, offering the driver to choose between Eco Pro, Comfort, Sport and Sport+ settings at the flick of a switch, as well as a front tower brace.
It runs on 19” Alpina Classic rims shod with Michelin Pilot Sports, over 370mm front and 345mm rear discs gripped by Alpina-branded callipers - four-piston in front, twin-piston at the rear.
The D3 is also available with a tweaked version of BMW's xDrive all-wheel drive system, tuned to dial out understeer and improve traction on variable surfaces.
STYLING & EQUIPMENT
The D3's deep-chested front apron has been designed to improve airflow to the various coolers and the brake ducts; Alpina describes its styling and trim updates to the 3 Series as 'sensible', including sports seats, climate control and xenon headlights.
The cabin is trimmed in special Lavalina leather (in any colour you can imagine) with discreet Alpina logos on the door sills, floor mats, seatbacks, the instrument cluster (which also features Alpina's signature blue backlighting) and the hand-stitched sports steering wheel.