The 2014 Alpina B4 Bi-Turbo Cabrio powers up luxury and speed

Tue, 04 Mar 2014

The BMW specialists at Alpina know how to exploit a niche when they see one. With the BMW M4 still not technically official, it saw the need for a higher performance four-seat convertible than the 435i 'vert. Enter the new B4 Bi-Turbo Cabrio that is debuting at the Geneva Motor Show.

The European-exclusive model takes BMW's 3.0-liter, twin-turbocharged inline-6 and massages it up to 410 horsepower and 442 pound-feet of torque, which is less power but more twist than the M4 would give buyers. Alpina's tend to be built more as quick, luxurious grand tourers, and the B4 Bi-Turbo gets is no different with an adaptive sport suspension and an eight-speed automatic. Plus it wears the classic pinstripes and 21-spoke wheels that are the brand's design hallmarks.

While the added weight for the convertible means that the Cabrio takes 4.5 seconds to reach 62 miles per hour, about a half-second slower than the coupe, at the moment it is the only way to get this kind of performance in a BMW convertible. Orders for the convertible open in March in Europe and prices in Germany start at 74,800 euros ($102,878 at today's conversion rates).

Alpina BMW B4 Bi-Turbo Cabrio

The foundation that Burkard Bovensiepen laid in the 1960s in the form of a performance-enhanced BMW 1500, has since developed into a permanent fixture in the luxury sports car segment.

What were then the first technologically advanced products marketed by Alpina, namely four-cylinder petrol engines with Weber dual carburettors, are now in modern form high-tech automobiles. Equipped from the outset with the best possible genes by BMW, they represent the ultimate in performance, comfort, driving culture and efficiency.

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.

Alpina BMW B4 Bi-Turbo Cabrio (2015)
2015 Alpina BMW B4 Bi-Turbo Cabrio
THE BMW ALPINA B4 BITURBO CONVERTIBLE

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 BMW ALPINA B4 BITURBO COUPÉ

The design of the B4 Bi-Turbo Coupé combines muscular and delicate elements in one chic silhouette. The Coupé is longer, wider and significantly lower than the Saloon. Its profile rakes from an imposing, muscular front accentuated with bold lines to a clean and stylish rear. The front spoiler, with subtle Alpina lettering, integrates seamlessly into the dynamic front apron which is characterised by large air intakes for the cooling system of the turbo-charged engine, the transmission and the high-performance fixed-calliper brake system. Together with the rear spoiler the Coupé's aerodynamics are optimised for excellent high-speed stability while simultaneously maintaining a low drag coefficient. It is almost as if the low, elongated silhouette of the Coupé was shaped to complement the 20" Alpina Classic wheels. Their timeless, twenty spoke design with hidden air valves suit the B4 Bi-Turbo exceptionally well. Blue brake callipers with Alpina lettering and signature twin tailpipes complete the appearance.

POWERTRAIN

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.

TRANSMISSION

Inspired by the pleasure that the 8-Speed Sport-Automatic Transmission with Switch-Tronic offers in the larger V8 powered BMW Alpina models, the so-called 8HP70 transmission has been extensively adapted to suit the performance characteristics of the new B4 Bi-Turbo models. Hardware modifications to ensure that maximum possible power delivery can be achieved include reinforced front and rear axle differentials, high-strength output and drive shafts and a high-torque transmission gear unit. In actual fact, the high power output and torque of the Bi-Turbo combine so well with this transmission that performance figures usually associated with much larger but less efficient engines are achieved. Furthermore, this transmission excels in disciplines often assumed to be incompatible and offers an optimum driving experience in every situation. To this end, three shift modes are available: Automatic (D), Sport (S) and Manual (M).

In Automatic (D) Shift Mode the focus is strictly on driving comfort. The transmission changes gears quickly and with no noticeable interruption to the delivery of power. The torque of the engine enables consumption-optimised 'surfing' in high gears even at very low speeds and in urban driving environments. Even at higher cruising speeds the rpms will remain low, for example 2500 rpm at 170 km/h in 8th gear, increasing long-distance driving comfort significantly.

Sport (S) Shift Mode noticeably shortens the time it takes for the next gear to engage and depending on engine load significantly moves the shift points up the rev range. Accelerator inputs are carried out immediately, full throttle i.e. kick-down will implement multi-simultaneous downshifts and optimal acceleration. When combined with the Sport or Sport+ setting of the Drive Performance Control, which modifies the drive and chassis setup, gearshifts are even quicker.

Activating the Manual (M) Shift Mode using the Switch-Tronic buttons on the back of the steering wheel, allows the driver to take control and shift gears when suitable or necessary. A special feature of the Sport, Sport+ and DSC Off setting is the suppression of automatic up-shift in Manual (M) Shift Mode - hereby the selected gear is held into the rpm limiter and the transmission will not up-shift into a higher gear.

High torque allows the use of a long rear axle ratio which in combination with the 8-Speed Sport Automatic Transmission and Auto Start Stop contributes significantly to achieving great fuel economy. Top speed is achieved in 7th gear.

EXHAUST SYSTEM

The stainless steel exhaust system which was developed in collaboration with Akrapovic is 7.5 kg lighter in comparison to its predecessor. The resonant, sporty sound of the exhaust system is controlled by an intelligent exhaust valve. This offers the driver the possibility to influence the sound experience via the Drive Experience Control button and facilitates the balancing act between emotional soundtrack and long-distance comfort. In Comfort Mode the exhaust valve remains closed up to 2500 rpm, beyond which it opens depending on engine load and rpm. In Sport Mode, however, the valve is permanently open and the B4 Bi-Turbo thrills with its distinctive aural character under hard acceleration - when additionally selecting Sport (S) or Manual (M) Shift Mode the exhaust will deliver an occasional burble on the overrun.

CHASSIS

The suspension set-up of the new B4 Bi-Turbo provides great ride-quality and comfort while simultaneously offering sharp and dynamic handling. The adaptive Alpina sport suspension solves this conflict of interest by means of electronically adjustable dampers in collaboration with performance springs, bump stops and stabilisers. The system allows the driver to use the Drive Performance Control (Eco Pro, Comfort, Sport, Sport+) to select the suspension setting and driving dynamics to match his mood.

The longer wheelbase and wider track at the front and rear provide the B4 Bi-Turbo Coupé with a more dynamic character from the outset. Subtle adjustments to camber, toe-in and elastokinematics result in a neutral chassis and very balanced handling. The 20" Alpina Classic wheels with Michelin Pilot Super Sport tyres combined with a front strut brace accentuate the Coupé's direct and precise turn-in.

The Drive Experience Control settings also influence other parameters which effect driving dynamics, such as the electric power steering (Servotronic) and the driving stability control (DSC and DTC) system. The latter is subject to a software coding which takes into account the specifics of the Alpina suspension and chassis.

The Variable Sports Steering from BMW, which comes as standard, has a progressive steering rack providing steering stability at high speeds but which requires significantly less steering input (turns of the wheel) when manoeuvring and parking.

Deceleration is taken care of by an 18" high-performance brake system with 370 mm discs at the front and 345 mm discs at the rear. Aluminium callipers (4-piston on front axle, 2-piston on rear axle) painted in blue and with Alpina lettering, in conjunction with high-performance pads, ensure fading stability and optimal pedal feedback.

AVAILABILITY and PRICING

The new BMW Alpina B4 Bi-Turbo Coupé and Convertible models are available to order from March 2014 onwards. Prices in Germany start at Euro 68.600,- for the Coupé and Euro 74.800,- for the Convertible, incl. 19% VAT ex-factory.

By Chris Bruce