BMW is one of the world’s outstanding engine producers. So why would a small, independent company called Alpina believe it could take those engines and make them even better — with the full warranted approval of BMW? And if they are so good, why doesn’t BMW achieve that improvement in the first place and wholly own Alpina as Mercedes-Benz does with its high performance AMG business?

This conundrum is compounded by the fact that Alpina engines are built down BMW’s M-Sport power unit production line (incorporating bespoke Alpina components), the two intermeshing seamlessly in the manufacturing process.

And Alpina cars are assembled on BMW production lines, too, again using tuned parts designed by Alpina’s 70-strong engineering team.

Explaining this unlikely synergism, Alpina CEO Andreas Bovensiepen, son of the company's founder, says there is no conflict of interests. Alpina models are created to complement the BMW range — notably the M cars — rather than compete with it, he asserts. BMW states that it, too, is very comfortable with the arrangement. Apparently it has no wish to absorb Alpina.

Alpina produces its own high performance versions of BMW's 3, 4, 5, 6 and 7 Series and X3 models. Once assembled each one is sent to the company’s Buchloe, Bavaria, HQ to be finished with Alpina’s individual trim and equipment. Alpina output is about 1500 units per year.

The company’s philosophy is to provide a custom-made option for both diesel and gasoline powered BMW models, with the emphasis on added engine output and low-speed torque but with emissions reduced. It also provides what the company describes as “outstanding refinement and luxury,” with handling based on almost five decades of bringing an individualistic focus to BMW’s own models.

All Alpinas have automatic transmissions. Pricing is crucial, so Alpina cars are positioned just below BMW’s M range.

Magic mit diesel und benzin

Powertrains are at the epicenter of Alpina’s individualization philosophy and an example of how it achieves its niche solutions is the I-6 D3 engine based on BMW’s all-aluminum 3.0-L N57 unit, which has the latest generation common rail system with solenoid injectors. The twin turbocharged diesel produces a claimed 257 kW (344 hp) at 4000 rpm and 700 N·m (516 lb·ft) peak, which is on tap from 1500 rpm to 3000 rpm.

Alpina claims CO₂ emissions of 139 g/km, and 5.3 L/100 km combined fuel consumption in the 3-Series-based sedan.

The D3 sedan has a claimed top speed of 278 km/h (173 mph) and 0-100 km/h acceleration of 4.6 s, impressive for a fully validated 5-seat, competitively priced production sedan.

Bovensiepen explains how some of this is done. For a start, induction air pressure losses for the diesel are down by 30% compared with the standard system: “Our engineers tapped the potential of this engine by optimizing the intake paths to minimize airflow throttling and by exploiting the achievable charge air flow and high injection pressures," he told Automotive Engineering. "Our intercooler on this powertrain is 46% larger than standard.”

He described how, in developing the D3 engine, Alpina engineers faced similar challenges to those they had addressed with the company’s B3 gasoline unit, notably optimization of temperatures and flows through the intake and exhaust systems. As with the gasoline engine, the two turbos are fed from larger intake ducts with optimized radii, allowing them to breathe more freely.

Engines for all Alpinas are developments of BMW’s current 6-cylinder gasoline and diesel units, with design modifications developed and validated by Alpina and its technical partners, including Mahle (pistons), Bosch (engine management), AKG (intercooler) and Akrapovič (exhaust system). The 8-speed automatic transmission used is heavily modified (with the full support of ZF), with some 20% of the components described by Alpina as having received design changes.

While the latest D3 forms a significant part of Alpina’s output based on the current F30 BMW 3-Series sedan and Touring models and the recently launched 4-Series coupe and convertible, gasoline engines make up the majority share. Producing a claimed 301 kW (404 hp) and a maximum 600 N·m (443 lb·ft), Alpina’s I-6 gasoline engine fitted to the B3 Bi-Turbo and B4 Bi-Turbo is developed from BMW’s 3.0-L N55 Valvetronic direct injection unit.

Turbocharger trickery

Central to Alpina’s engine development is a move from the standard single turbo to two smaller components from Mitsubishi Heavy Industries, each exiting through its own close-coupled catalytic converter. Suitable mounting flanges for the turbos, and connections for oil and coolant, are provided by a bespoke crankcase developed with casting specialist BMW Landshut. The new geometry also accommodates the changes associated with the revised ZF 8HP70 transmission.

Bovensiepen explains that the smaller turbos spin up more quickly to a 1.2 bar (17.4 psi) maximum, offering the potential for very fast throttle response, combined with sufficient throughput for increased torque. Taking advantage of this capability required substantial optimization of the induction system to maximize flow and minimize airflow throttling.

“We integrated a 61% larger air-to-air intercooler with flow-optimized collector boxes and ducting, both on the ambient and pressurized sides of the system,” he explained.

Although flow is up 30% compared with the standard induction system, packaging the installation into the 3-Series engine bay was not easy, Bovensiepen stated: “We had to redesign the front subframe!”

Even with the new twin-turbo installation, the quest for the “always-available” power delivery characteristic of a large, naturally aspirated engine continued to be pursued at Buchloe.

Alpina developed its own air guidance to the turbochargers, including the electronically controlled recirculation air valves, and fits its own engine control unit with adapted management software and colder rated NGK spark plugs. To ensure high durability, a new high strength forged steel crankshaft was specified and the oil and water cooling systems substantially uprated.

The result of all this is very rapid performance for the B3: 0-100 km/h in 4.2 s and a maximum speed of 305 km/h (189 mph). The B3 sedan produces 177 g/km CO₂ on the EC drive cycle. Combined fuel consumption is a claimed 7.6 L/100 km.

With so much energy being unleashed, to ensure durability and thermal stability under all driving conditions, highly effective cooling system performance is vital. As with the gasoline car, the diesel uses bespoke high capacity heat exchangers for oil and water mounted behind a new front spoiler developed in BMW’s wind tunnel. Air is ducted efficiently through the units as well as optimizing the car’s aerodynamics. Thermal systems management is provided by a dedicated control unit.

On the hot side of the engine, accommodating the higher exhaust gas temperatures required a new exhaust manifold made from Ni-Resist D5S, an austenitic ductile iron alloyed with nickel to give superior high temperature strength. It allows peak temperatures to be increased by 50˚C. As with the gasoline engine, a lightweight, quad-outlet exhaust system, developed with specialist supplier Akrapovič, is optimized for gas flow as well as for acoustic characteristics, which are enhanced “during spirited driving” by opening a computer-controlled valve.

Returning to a central part of Alpina’s raison d’etre, Bovensiepen underlined that his company’s engines are not just about all-out performance. “We prioritize high torque from low engine speeds to give a broad useable rev range," he asserted. "This provides both smooth and sporting driving characteristics. At the same time, our engineers must reduce fuel consumption and emissions. The target is always to make our cars the most efficient in their category.”

Alpina has applied equal consideration to many other aspects of its vehicles. Bespoke suspension springs with a 40% higher rate work with bespoke roll-control bars, bushings and bump stops. The four-setting variable damper control has been recalibrated to provide softer compression and stiffer rebound, working with 35-series tires that have 20% softer sidewalls. Front camber and toe-in are optimized, a front body strengthening brace is fitted and there are Brembo brakes to Alpina’s specification.

“We have a clear picture of an Alpina buyer and optimize the car for him or her, without compromising to accommodate other tastes and specifications,” concluded Bovensiepen.