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Once the World's Fastest Sedan, the Alpina B10 Bi-Turbo Embarrassed a Testarossa

Back in 1989, Bimmer enthusiasts who wanted a sedan that was faster and more exclusive than the standard M5 could get the B10 Bi-Turbo. Dubbed the fastest production four-door in the world back then, it’s remembered for putting a Ferrari Testarossa in its place during an independent test.
Alpina B10 Bi-Turbo 13 photos
Photo: Alpina Burkard Bovensiepen GmbH & Co. KG
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Since its inception in 1972, BMW’s M division has blessed high-performance fanatics with some incredible rides. It all started with race-bred icons like the 3.0 CSL and the M1, but by 1980, engineers decided to showcase their skills on a four-door sedan platform, that of the E12 5-Series, creating the awesome M535i. The same formula was applied to the new E28 generation in 1985, giving birth to the first-ever M5.

In 1988, the second M5, built around the E34 platform, hit the streets. With a six-cylinder that made up to 311 hp (315 ps), it was the most powerful road car BMW had ever produced. It offered a nearly-perfect combination between a high-end sedan and a thoroughbred sports car, which made it extremely popular. When it was discontinued in 1995, it was the second best-selling M model in history, behind the legendary E30 M3.

But the M division wasn’t the only team of engineering wizards that transformed the standard E34 5-Series into a spectacular high-performance machine. About 43 miles from BMW’s headquarters, in a small town called Buchloe, Alpina completed what was the most ambitious project that the company had ever undertaken: the B10 Bi-Turbo.

Based on the 535i, not the M5

Alpina B10 Bi\-Turbo
Photo: Alpina Burkard Bovensiepen GmbH & Co. KG
While they could have slapped a pair of turbos on the standard M5 and called it a day, Alpina engineers opted to develop their own high-performance series from the ground up and reportedly spent $3.2 million (over $7,7 today) to make it happen.

They started in late-1987 with the newly-introduced 535i E34 sedan, which was given a complete makeover in terms of both performance and looks.

After approximately two years of hard work, Alpina revealed a limited-production sedan that was not more powerful than the M5, but, true to the company’s philosophy, it combined ridiculous performance figures with high-end luxury, road manners, and reliability that one normally doesn’t expect from an M-badged BMW.

A wide range of improvements, including a rebuilt six-cylinder

The Alpina\-Tuned M20 on the Test Bed
Photo: Alpina Burkard Bovensiepen GmbH & Co. KG
From the outside, the B10 Bi-Turbo distinguished itself from the 535i and M5 models thanks to bespoke bumpers, side skirts, a rear spoiler, and, of course, Alpina’s iconic spoked wheels, as well as the subtle side decals.

The cabin was a lot more luxurious than that of the M5, boasting leather-upholstered, fully-electric Recaro seats, woodgrain trims, and a custom Momo steering wheel highlighted by the Alpina badge.

But, unquestionably, the most exciting upgrade was found under the hood. The company’s engineers took the stock naturally-aspirated M30 six-cylinder that powered the 535i and turned it into a twin-turbo monster. They started by adding forged Mahle pistons, stronger conrods, and a redesigned cam, then re-balanced every single moving part and re-machined the combustion chambers. In addition, the Alpina engineers redesigned the intake and exhaust systems, the latter of which got a pair of Garret T25 turbos cooled by a huge front-mounted intercooler.

The chassis was also upgraded to cope with the added power without sacrificing comfort. The suspension system got new springs, beefy anti-roll bars, sportier Bilstein front dampers, and self-leveling rear units manufactured by Sachs. Moreover, the stock front brakes were replaced with Girling 4-piston calipers that hugged 13.1-inch (332.7 mm) rotors – bigger than those found on the M5.

The German sedan that embarrassed a V12-powered Ferrari

Alpina B10 Bi\-Turbo vs\. Ferrari Testarossa
Photo: Alpina Burkard Bovensiepen GmbH & Co. KG
The Bi-Turbo’s revamped 3.5-liter was capable of spitting out 355 hp (360 ps) and 384 lb-ft (520 Nm) of torque. That made it more powerful than both the 1988 M5 and the revised 1992 version, which came with an improved S38 engine that made 335 hp (340 ps) and 295 lb-ft (400 Nm) of torque. With these figures, it dethroned the M5 as the most powerful BMW road car ever produced and Alpina claimed that it was the fastest sedan that money could buy.

The German automotive magazine Sport Auto wanted to put that claim to the test, but rather than comparing it to contemporary sedans, they chose to test the Bi-Turbo alongside a V12-powered Ferrari Testarossa.

Although the prancing horse was four years older, it was about 110 pounds (50 kg) lighter and its engine was slightly powerful, delivering 385 hp (390 ps). But, despite this, when the head-to-head, straight-line speed test commenced, the German sedan was faster off the line, reaching 62 mph (100 kph) half of a second quicker, and staying ahead up to 100 mph (160 kph). The exotic Italian sports car managed to pass it when it reached 124 mph (200 kph), but that didn’t rub out the embarrassment of being slower off the line than a German sedan.

A used one in good shape is not as expensive as you think

Alpina B10 Bi\-Turbo
Photo: Alpina Burkard Bovensiepen GmbH & Co. KG
Apart from being blistering quick for its era, the B10 Bi-Turbo was praised for its comfort and precise handling. While an M5 had an aggressive demeanor that made those behind the wheel feel like they were driving a sports car, the Alpina felt well-mannered and surprisingly smooth – especially for a turbocharged car.

It was produced for five years, from 1989 to 1994, in only 507 units. Alpina wanted to continue production beyond 1994, but was forced to stop by BMW’s decision to drop the M30 engine.

Considering its rarity, you would expect a surviving example of this Ferrari slayer to be a highly sought-after collector’s item that demands well over the $100,000 mark. However, this is not the case, as several well-kept Bi-Turbos which popped up at auctions in recent years sold for less than $50,000. That’s a small price to pay for such an epic car, so if you’re a fan of old-school, high-performance sedans and you have the means, an Alpina B10 Bi-Turbo is well worth the investment.

If you’re still not convinced of how awesome this car still is, 34 years after it was introduced, I recommend watching the YouTube video below by ECS Tuning.

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About the author: Vlad Radu
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Vlad's first car was custom coach built: an exotic he made out of wood, cardboard and a borrowed steering wheel at the age of five. Combining his previous experience in writing and car dealership years, his articles focus in depth on special cars of past and present times.
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