The B5 (2005) is based on the 545i and uses a modified version of its 4.4-litre valvetronic V8 engine designated by Alpina as the H1 (shared with the B7 and B6).Changes to the engine include an Alpina specific block made by Steyr, a forged crankshaft and low compression Mahle pistons.The engine retains the valvetronic system and uses a centrifugal-type supercharger, made by ASA to Alpina's specifications the supercharger is belt-driven by the crankshaft and has a boost pressure of about 0.8 bar (11.7 psi). The supercharger was added to eliminate lag in power delivery during every day use. The modified engine has a power output of 500 PS (368 kW; 493 hp) at 5,500 rpm and 700 N⋅m (516 lb⋅ft) from 4,250 to 5,250 rpm. The engine has a red-line of 6,000 rpm.
The B5 comes with 19-inch forged multi-spoke alloy wheels and Michelin Pilot Sport 2 tyres measuring 245/40 ZR19 at the front and 275/35 ZR19 at the rear.The B5 has Alpina's own suspension system designed to give a soft ride in normal driving conditions. The brakes used on the car were taken from the Middle-Eastern specification 760Li.
Exterior changes over a regular 5 Series included a front chin spoiler with Alpina lettering and optional Alpina pinstripes on the exterior paint. The interior came standard with Lavalina leather upholstery, wood trim, BMW iDrive system, Alpina gauges, perforated Alpina sports seats and Alpina badging throughout. The interior was fully customisable by the Alpina interior department.
