The V16 that BMW secretly built

It was a Cold War, a veritable arms race between two arch-enemies: Daimler-Benz and BMW. In the late 1980s, BMW developed a secret weapon that was never used – a 16-cylinder engine. The foundation for this was laid in 1972, when BMW engineers started working on the development of a V12. After that, two oil crises threw a spanner in the works. Halfway through the years, the BMW brand in the top segment was therefore not completely taken for granted. The top model from 1980 was the 745i with its widely produced six-cylinder engine, which initially had a displacement of only 3,210 cubic centimeters and later 3,430 cubic centimeters. Thanks to a turbo, the engine still delivered a power of 252 hp. The mayor of Munich might be able to handle that, but in the rest of the world politicians and other important people were transported in cars that had at least a five-liter V8 under the hood. As a result, Mercedes-Benz was still the master of this segment.

In 1987, however, BMW hits back hard: a twelve-cylinder makes its appearance in the 7-series. The BMW strategists then await Daimler’s reaction with trembling knees. Will Stuttgart come up with a bigger twelve-cylinder? Chances are high, so they can’t sit back in Munich. Karlheinz Lange was the head of the powertrain development department at the time. “We wanted to have alternatives available in case our competitors came up with a V12 engine shortly after the start of series production. We wanted to come up with a superlative once again in such a situation.” That could have happened with a biturbo V12, after all, BMW had experience with turbo technology. The other option: a V16. From a contemporary point of view, that may seem like a delusion of grandeur, but it was actually a very obvious move. “The cylinder bank angle of our 12-cylinder M70 M70 is also optimal for a V16,” says Lange.

On July 8, 1987, the engineers received the green light for the development of the V16. The construction would have to take place in the utmost secrecy. Lange only informed a few BMW engineers and a handful of experts from suppliers such as Bosch and the foundry that had to make the oversized sump. The team even worked in a place that was far removed from the rest of BMW’s development department. Nobody was allowed to get anything from it, in the beginning not even the management of the brand. Nothing was recorded in the construction lists. In order to guarantee secrecy, the engine was also not given a type designation as M70 as usual. Instead, the team gave the project a very special code name: ‘Goldfisch’.

The V16 shared cylinder spacing, bore and stroke as well as camshaft drive times with the M70 12-cylinder. The four extra cylinders increased the displacement from five to 6.7 liters. In the spring of 1988, ‘Goldfisch’ was first tested on the test bench. The measured power: 408 hp and with some measurements even powers of 430 hp were measured. Thanks to the aluminum engine block, the V16 weighed a total of 310 kilograms – the horsepower-to-weight ratio was thus 0.76 to 0.72 kg/hp better than that of the twelve-cylinder, where this ratio was 0.83 kg/hp. The next challenge: mounting the engine in a test car. Team Goldfisch plunged into a 735iL in the extended version, which was painted in the color ‘Nerzbraun Metallic’. For the test work on the public road, they built in the most robust transmission that the supplier could supply: a manual six-speed gearbox. In order for the V16 to fit in the engine compartment at all, the engineers had to move many components that served for cooling to the trunk. This confirmed that the engine with the accompanying cooling system would not fit in a standard 7-series due to its immense dimensions, a completely new model range would have to be developed.

Conceivable were a mid-engine sports car with a transverse engine, just like the Cizeta unveiled in 1989, or a super luxury limousine that would come above the 7-series in the range. That model finally debuted in 2003 as the Rolls-Royce Phantom, which was developed under BMW’s leadership as a competitor to Daimlers Maybach. In any case, it would have taken at least another five years for the development and testing work. At that time, however, even the highest bosses did not know about the existence of project Goldfisch. That changed in the year after the project started. In the summer of 1988, Wolfgang Reitzle, member of the executive board and head of BMW’s development department, was invited for a test drive with a “particularly powerful 7-series motorized vehicle”. At first, nothing more was said about it. Karlheinz Lange recounts a situation that seems straight out of a movie: “To hide the large air intakes in the rear, a couple of engineers stood in front of that part of the car just before Reitzle got in.”

The specifications of the engine were only announced after the test drive through Munich. Reitzle was impressed by the enormous power and torque of 625 Nm. Despite this, the management did not agree to the development and serial production of a suitable chassis. It was over and out for the V16. Disappointed, the engineers rolled the mink-brown Goldfisch into the warehouse. The test model only had a few kilometers on the clock, after all, no endurance tests were done with it and the performance was not measured either. It is very doubtful whether you would still be able to walk around the block with this unique piece of technology today. You probably need to replace everything first. The unique thing has not been started since the demonstration rides almost twenty years ago.

But how did the arms race actually go on? Slower than they had feared at BMW: it was not until 1991 that Mercedes-Benz presented its first post-war twelve-cylinder in the 600 SE. The engine in the ‘Cathedral’, however, immediately delivered a power of 408 hp. BMW, however, did not pick up the gauntlet anymore; the new 750i that came on the scene in 1994 had only 326 horsepower. Mercedes-Benz in turn caused a surprise in 1999 with the S600, which with a capacity of 367 hp was less muscular than its predecessor. However, the horsepower battle would flare up again shortly afterwards. At the other end of the spectrum, BMW developers have been working on a three-cylinder since the 1980s. However, that engine was unable to win the battle with the four-cylinder internally, because its running characteristics were less good. That is of course long gone, nowadays BMW is at the forefront of the arms race with regard to limiting CO2 emissions.

This article previously appeared in AutoWeek Classics issue 10 from 2017. Curious about the other manufacturers who started working with a V16? Then be sure to read this episode of The Flight Strip!