BMW M8 E31 Prototype (1990)

The BMW M8 E31 Prototype, developed in secret in the early 1990s, was a raw, high-performance evolution of the 8 Series grand tourer — a car that BMW never officially released but that became legendary among enthusiasts. Designed to rival Ferrari and other supercar brands, the M8 was meant to be the ultimate expression of the 8 Series platform, featuring a bespoke V12 engine, track-oriented modifications, and motorsport DNA. For decades, its very existence was shrouded in mystery until BMW finally unveiled the prototype to the public in 2010.

History

The E31 8 Series, launched in 1989, was BMW’s most technologically advanced model at the time — a luxury GT car with pop-up headlights, a sleek wedge design, and cutting-edge electronics. But internally at BMW M GmbH, a more radical idea was brewing: build a version of the 8 Series that could compete with the Ferrari Testarossa, Lamborghini Diablo, and Porsche 959.

In the early ’90s, the M Division secretly developed what they referred to internally as Project 8. This project aimed to transform the 850CSi into a true supercar: lighter, more powerful, and sharper in every way. Engineers stripped it down, built a new engine, and created a one-off prototype that would become known as the BMW M8.

Despite reaching a fully functional prototype stage, the project was cancelled before production due to high costs, lack of market feasibility, and a looming global recession. BMW feared that a supercar priced well above the standard 8 Series would not be viable in a shrinking luxury market.

Design Features

While the M8 shares its silhouette with the standard 8 Series, virtually every visible panel was either modified or replaced. The prototype features fixed headlights instead of the pop-up units, with composite covers and integrated intakes to reduce weight and improve airflow. The front bumper was reshaped for better aerodynamics, and the hood gained large twin NACA ducts to help cool the monstrous V12 underneath.

Wider fenders accommodated larger wheels and track-ready tires. The rear end featured a deep diffuser, dual exhausts, and a deleted BMW roundel — a statement of anonymity and purpose. The side windows were made of lightweight Lexan, and most of the trim pieces were removed or replaced with carbon fiber components.

Inside, the M8 was stripped for performance. It had racing bucket seats, a bespoke dashboard with analog gauges, no infotainment, and minimal insulation. A roll bar, fire extinguisher, and exposed structural elements made clear that this was no GT — it was a prototype track weapon in disguise.

Specs

At the heart of the M8 prototype was a bespoke 6.1-liter V12, internally designated S70/1 — not to be confused with the later S70/2 used in the McLaren F1. This engine was heavily modified from the M70 5.0L V12, with new heads, four valves per cylinder, individual throttle bodies, and a high compression ratio.

Key specifications:

Engine: 6.1-liter S70/1 V12, naturally aspirated
Power output: approx. 550 horsepower
Torque: over 500 Nm
Transmission: 6-speed manual
Drivetrain: Rear-wheel drive
Weight reduction: Estimated 250–300 kg lighter than standard 850CSi
0–100 km/h: ~4.5 seconds (estimated)
Top speed: estimated over 300 km/h (186 mph)

Chassis upgrades included stiffened suspension, larger brakes, reinforced subframes, and altered geometry for sharper turn-in and high-speed stability.

Production Status

Only one true M8 prototype was ever built. For decades, its existence was denied or downplayed by BMW. The car was stored in a locked facility under a cover, fueling rumors and speculation among enthusiasts and journalists.

Finally, in 2010, BMW lifted the curtain during a press event at its Garching facility, revealing the M8 in full. The car is now preserved in BMW’s Group Classic collection and occasionally appears at special events or exhibitions.

Though the M8 never reached production, the S70/2 engine based on this prototype’s block went on to power the McLaren F1, making the M8 a key stepping stone in one of the most legendary engine development paths in history.

In a symbolic sense, the 2019 BMW M8 (G15) — the first production M-badged 8 Series coupé — fulfilled the promise that the 1990 prototype hinted at decades earlier.

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