Car companies build strange prototypes all the time. Most of them never leave the factory, and many are destroyed once testing is finished. A few survive quietly in storage rooms or private collections. But once in a while, one slips through and turns into a story worth telling.
This is one of those stories. In the early 2000s, engineers at Volkswagen created a one-off prototype that sounds almost too strange to be real. They took a BMW M5 and installed a ten-cylinder W engine under the hood. Yes, a Volkswagen-powered BMW M5.
For years, the car lived in rumor territory. People had heard whispers about it, but very few had actually seen it. Eventually, the prototype surfaced and proved the story was real. Now it stands as one of the strangest engineering experiments of its era.
When Volkswagen Engineers Had No Limits
The company was run by the legendary Ferdinand Piëch, a man known for pushing engineers far beyond the norm. Piëch believed that ambitious engineering projects could elevate the entire brand. Under his leadership, the company experimented with some truly unusual ideas.
This was the golden era of Volkswagen’s famous W engines. Engineers developed the W8, W12, and W16 configurations that later powered a range of vehicles across the Volkswagen Group. These engines were compact but extremely complex. They represented the kind of technical experimentation that defined the Piëch era.
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Images: GDM Motors
The W8 appeared in the Volkswagen Passat W8, a strange but fascinating luxury sedan with an unusually compact eight-cylinder engine. It even came with a manual gearbox and a wagon body. The W12 found its way into several high-end models across the group, especially in luxury platforms. The ultimate version of this engineering philosophy became the W16 used in the Bugatti Veyron. That engine would go on to power one of the most famous hypercars ever built.
Volkswagen engineers were experimenting with more than just W engines during this period. The company also built diesel SUVs with massive V10 and V12 engines. There was even an experimental Audi R8 V12 TDI concept that never reached production. The company was willing to try almost anything if the engineering challenge looked interesting enough.
Among those experiments was something even rarer. Engineers developed a W10 engine that never reached production. Only a handful of prototypes were built, and the project required a real car for testing. That decision eventually led to one of the most unusual test vehicles ever created.
Why Volkswagen Used A BMW M5
At the time, Volkswagen did not have a suitable performance sedan platform ready for development testing. Engineers wanted to evaluate the W10 engine in a real-world environment. But the company lacked a chassis that could deliver the performance they expected. Instead of building one from scratch, they took a shortcut.
Volkswagen purchased a third-generation BMW M5 and turned it into a test mule. It may sound odd, but the choice made perfect sense from an engineering perspective. The E39 M5 was widely respected for its balance of performance, handling, and durability. It was also considered one of the best sports sedans of its time.
The engine bay offered enough space to fit the experimental W10. The compact layout of the W configuration made it easier to package than a traditional V10. Engineers could install the engine without completely redesigning the car's front structure. That saved significant development time.
Another reason was the car’s driving dynamics. The E39 M5 already had excellent chassis tuning and strong suspension components. Volkswagen engineers could focus on evaluating the engine instead of reworking the entire vehicle. The car’s understated design also helped keep the prototype discreet during testing.
The six-speed manual transmission was another big advantage. Engineers wanted full control over how the engine behaved under load and acceleration. A manual gearbox enabled them to test the engine more directly. It also made the car more engaging to drive during development.
A Wild Experimental Engine
The real star of the project was the experimental W10 engine itself. Reports suggest the engine displaced roughly five liters. It was created by combining two 2.5-liter VR5 engines into a single W configuration. Unlike many VR engines of the time, this prototype used a cast aluminum block.
The compact layout was one of the main advantages of the W engine design. It allowed engineers to package a ten-cylinder engine in a relatively small space. That was part of the reason it could fit into the BMW’s engine bay. The design was complex but surprisingly efficient in terms of size.
Power output was impressive for the time. On a dynamometer, the prototype produced about 480 horsepower and 436 lb-ft of torque at the wheels. When drivetrain losses are considered, that suggests roughly 530 horsepower at the crank. That figure made the car significantly more powerful than the original E39 M5.
For comparison, the original E39 M5 used a 4.9-liter S62 V8 engine producing 394 horsepower at the crank. Several years later, BMW introduced the V10-powered BMW M5 with the S85 engine rated at 500 horsepower. Volkswagen had essentially built something even more powerful before BMW reached that milestone. It was an impressive demonstration of what the W10 concept could do.
A Luxury Sedan With Rough Edges
Even though the engineering work looked clean, the car was still a prototype. Many of the comfort and safety systems normally found in production vehicles were missing. The car did not have stability control. It also lacked ABS and traction control systems.
That meant all the power went straight to the rear wheels with almost no electronic assistance. For experienced drivers, that might sound exciting. For everyone else, it probably made the car extremely difficult to handle. With over 500 horsepower available, things could get sideways quickly.
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Images: GDM Motors
Inside the cabin, the car's experimental nature became even more obvious. The instrument cluster looked more like a race-car setup than a luxury sedan's. Several additional gauges were mounted on the center stack to monitor engine performance. Engineers also used a standalone ECU to control the drivetrain.
The cabin was far from refined. Reports suggest that fuel and exhaust fumes can sometimes enter the car. That was not exactly ideal for daily driving. But the raw mechanical character probably made the experience unforgettable.
Ferdinand Piëch’s Personal Test Car
One of the most interesting details about this prototype involves who actually drove it. According to reports, Ferdinand Piëch himself used the car as a personal daily driver for a period of time. Officially, he was testing the engine to evaluate its real-world performance. Unofficially, he was probably just enjoying the drive.
Piëch was known for being deeply involved in engineering projects across the Volkswagen Group. He was not the type of executive who stayed in an office all day. Instead, he often drove experimental vehicles to evaluate them personally. That hands-on approach helped shape many famous projects.
His influence on the automotive world was massive. He played a major role in developing Audi’s five-cylinder engines and helped launch the legendary Audi Quattro rally program. Later, he oversaw the engineering push that produced vehicles like the Bugatti Veyron. Driving a secret W10-powered M5 probably felt like the perfect company car.
The Prototype That Refused To Disappear
For many years, the W10-powered M5 was little more than an automotive legend. Enthusiasts had heard stories about it, but the car itself rarely appeared in public. Eventually, the prototype surfaced again and attracted attention from automotive media. One detailed look came from DriveTribe, which tracked the car down and documented it.
The car was located in Belgium and owned by a collector deeply interested in Volkswagen’s W engines. The owner reportedly also possessed one of the other known W10 engine blocks. That makes the collection incredibly rare in automotive terms. Very few examples of this engine are believed to exist.
This car represents a forgotten chapter of experimental engineering. It is a one-of-a-kind test vehicle from one of the most ambitious periods in modern automotive history. A Volkswagen-powered BMW M5 with a ten-cylinder W engine is exactly the kind of strange idea that could only happen during the Piëch era.
And that is exactly why enthusiasts still find it fascinating today.
