2015 Alpina BMW B4 Bi-Turbo Cabrio - Review And Design

The new BMW Alpina B4 Bi-Turbo models combine these characteristics like no other. The modern straight-six 3 litre engine equipped with two turbochargers produces 301 kW (410 hp) and a maximum torque of 600 Nm. The adaptive Alpina sport suspension and the 8-Speed Sport-Automatic Transmission with Alpina Switch-Tronic deliver maximum comfort and impressive dynamics. Functional aerodynamics, signature 20" Alpina Classic wheels and two elliptical double tailpipes are hallmarks of the Alpina design philosophy.

The perfect interaction of power, torque and high-tech transmission impresses with phenomenal acceleration and a top speed in excess of 300 km/h while simultaneously allowing for relaxed long-distance cruising. All the time a real life consumption of below 10 l per 100/km is easily achieveable - in fact the new B4 Bi-Turbo Coupé achieves a class-leading combined fuel economy of just 7.6 l/100 km and 177 g/km CO2.

These extraordinary performance figures are also available for customers wishing all-wheel drive. The BMW Alpina B4 Bi-Turbo Coupé is available with the excellent BMW xDrive system which offers unparalleled levels of traction and driving dynamics.

The Alpina philosophy rests on a number of central pillars including effortless performance, abundance of torque, smooth automatic transmissions, an emotional soundtrack and precisely tuned suspensions. This in summary sophisticated driving experience with a sporty touch is perfectly suited for elegant convertibles where an open roof amplifies all sensations. Hence it is not without reason, that BMW Alpina Convertibles based on the BMW 3 Series have a small and particularly loyal group of enthusiastic owners who share a passion. The new B4 Bi-Turbo Convertible carries on this legacy with its impressive performance, driving dynamics and elegant silhouette.

The design of the B4 Bi-Turbo Convertible is characterized by short overhangs, precise, long-drawn-shoulder lines, a wide rear and the characteristic metal folding roof. The sporty and purposeful design of the front spoiler is dictated by functional air intakes and operates in conjunction with the modest rear spoiler to improve stability at high speeds. When the roof is open the B4 Bi-Turbo Convertible stands out with its sleek, clean look. The Alpina Classic 20" light alloy wheels fit seamlessly into the overall shape of the Convertible and lend it a particularly elegant presence.

It only takes 20 seconds and the press of a button to close the roof, which is possible up to a speed of 18 km/h, turning the Convertible into a winter- and weather-proof two-door. The shape of the roof line when closed differs from the B4 Bi-Turbo Coupé significantly due to the steeper rake of the rear windscreen, the flat boot lid and subtle rear spoiler - this gives the Convertible a very distinctive and stand-alone appearance.

The 2979 cc straight-six cylinder engine with high-precision direct injection, Valvetronic and Bi-Turbo charging delivers 301 kW (410 hp) between 5500 rpm and 6250 rpm and a maximum torque of 600Nm at only 3000rpm. In fact impressive 550 Nm are available across a wide range between 2200 rpm and 5200 rpm. In combination with the excellent ZF 8-Speed Sport-Automatic Transmission this means that the B4 Bi-Turbo models are never lacking in forward momentum - power can be called upon at all times and in an instant, in order to enjoy that typical, effortless Alpina driving experience.

The B4 Bi-Turbo Convertible accelerates in 4.5 seconds, the B4 Bi-Turbo Coupé All-Wheel Drive in just 4.0 seconds from 0 to 100 km/h on their way to a top speed in excess of 300 km7h. The B4 Bi-Turbo Coupé passes the 200 km/h mark in only 14.1 seconds. The drivetrain, equipped with Auto Start Stop and Valvetronic, also impresses with class-leading economy figures of just 7.6 (8.0) litres per 100 km and 177 (186) g/km of CO2 measured according to ECE Norm.

The prerequisite for these impressive values is a high-tech engine which exhibits its own unique characteristics thanks to a significant number of stand-alone features. With the aim of achieving excellent responsiveness, high output acrosas the entire rpm range and an improvement in fuel consumption, a Bi-Turbo engine configuration was required. This type of turbocharging has the benefit of providing very good response and pick-up due to the low mass moment inertia of the turbocharger's running gear and sufficient rate of air-flow for maximum power delivery. The design and construction of the excellent BMW 3.0 litre straight-six cylinder (N55) engine serves as a starting-point for a specially cast aluminium block with Bi-Turbo capable flanges. These enable the mounting of two turbochargers along with required oil and water connections and a close-coupled catalytic converter arrangement. Alpina specific NGK spark plugs and a forged steel high-strength crankshaft guarantee long-lasting stability. Always-on power delivery and excellent throttle response are aided by an electronically controlled bypass valve system. Specially constructed, flow and cross-section optimised air intake ducts guide the air with minimal losses from the air intake via the air filter housing to the turbochargers. On the fuel side, a high-performance high-pressure fuel pump ensures the right throughput. Optimal utilisation of the output is provided by a high-capacity intercooler with flow-optimised collector boxes made from aluminium. Water cooler, additional separate water and engine oil coolers as well as a high-performance cooling fan ensure the thermal stability of the cooling system in all conditions.