The Saab 93 Monstret: How a Twin-Engined Prototype Defined an Eccentric Legacy

The Genesis of an Automotive Frankenstein

In the pantheon of automotive what-ifs, few machines command the same blend of awe and terror as the Saab 93 “Monstret.” Conceived in the late 1950s, this prototype was not a product of market research or corporate strategy but of raw, unadulterated engineering curiosity. It represents a pivotal moment where Saab’s aviation-bred ethos collided with the brutal realities of international rallying, producing a creature that was less a car and more a controlled explosion on wheels. To dismiss the Monstret as a mere curiosity is to miss its profound significance: it was the physical manifestation of a question that haunted Saab’s engineers—how do you conquer the world’s toughest stages without sacrificing the front-wheel-drive integrity that defined your brand? Their answer was to bolt two engines together and point them at the problem.

Dissecting the Beast: Technical Specifications and Madness

The foundation was the production Saab 93, a car already celebrated for its aerodynamic teardrop shape and front-wheel-drive prowess. The modification, however, was an act of automotive heresy. Engineers removed the standard 748 cc three-cylinder two-stroke engine and installed a second, identical unit transversely alongside it. This created a de facto 1.5-liter six-cylinder two-stroke powerplant, a configuration never before or since seen in series production. The combined output was rated at approximately 138 horsepower—a staggering figure for an era where a typical family sedan struggled to breach 60 hp. In a vehicle with a curb weight estimated just under 1,500 pounds, the power-to-weight ratio was nothing short of explosive.

This mechanical marriage required a host of radical, last-minute adaptations. The standard three-speed gearbox was retained but heavily modified, a decision that would prove catastrophic. The immense, instantaneous torque from the twin mills regularly sheared transmission components, turning the gearbox into a potential liability rather than an asset. To manage the anticipated heat, the radiator was relocated to the front of the firewall, behind the engine assembly—a layout that complicated cooling and weight distribution. The body saw extensive modification: steel panels were replaced with aluminum and fiberglass to shave critical pounds, and the interior was stripped to a bare, functional skeleton. The result was a car that emitted a piercing, metallic six-cylinder two-stroke wail and a constant plume of blue smoke, announcing its presence from miles away.

The Architecture of Instability

The most critical and damning flaw was inherent in its very conception. By packaging two complete engine assemblies over the front axle, engineers created a severe weight distribution nightmare. The front end became grotesquely overloaded, fundamentally altering the car’s dynamic character. This wasn’t just understeer; it was a violent, uncommunicative push toward the nearest obstacle the moment the throttle was engaged. Compounding this was legendary torque steer. When both two-stroke engines inevitably hit their narrow power bands simultaneously, the steering wheel would wrench violently in the driver’s hands, transforming precise input into a battle for survival. The Monstret was fast in a straight line—officially clocked at 122 mph at the Såtenäs airfield—but it was a liability everywhere else.

Rallying Context: The Problem That Spawned a Monster

To understand the Monstret, one must understand the rally landscape of the late 1950s. Saab, with its nimble, front-wheel-drive 93 driven by the legendary Erik Carlsson, had mastered the technical, twisty stages. The car’s lightweight and superb handling made it a giant-killer on events like the RAC Rally. However, on the fast, open stretches of continental European rallies—the high-speed “special stages” that decided championships—the small-displacement two-stroke ran out of breath. Competitors with larger, more powerful engines, often rear-wheel drive, would pull away on the straights, erasing the time gains Saab accumulated in the corners.

Saab’s engineering philosophy, rooted in aircraft principles, sought a solution that preserved the crucial front-wheel-drive advantage for traction on loose surfaces. Adding a single, larger engine would have meant a complete chassis redesign. The twin-engine solution was a brute-force hack: double the displacement, double the cylinders, and keep the drivetrain layout. It was a testbed, a “laboratory experiment rat” as the source material aptly states, designed to answer one question: could the 93 chassis handle the power? The answer, delivered with terrifying clarity, was a resounding no.

Design and Ergonomics: Form Follows Folly

Externally, the Monstret was a subtly bulged version of the standard 93, betraying its secret only to the most observant. The true story was told inside. Where a driver expected a single engine’s hum, they were met with the cacophony of two. The smell of premix oil and burnt two-stroke fuel was pervasive. The dashboard was stripped of all but the most essential gauges, their needles likely dancing erratically under the twin-engine vibration. The steering column, gear lever, and pedals transmitted a constant, violent shudder. This was not a car for comfort; it was a cockpit for a stress test. The decision to use aluminum and fiberglass body panels, while saving weight, further contributed to a chassis that likely lacked the torsional rigidity to cope with the forces being generated, exacerbating the handling maladies.

Why It Failed: The Triumph of Pragmatism

The Monstret’s demise was not a lack of courage but an acceptance of physics. The project was shelved for several interconnected, insurmountable reasons. First, the transmission was a ticking time bomb. The bespoke gearbox could not reliably transfer the twin engines’ explosive torque to the front wheels without catastrophic failure. Second, the handling was fundamentally unsafe for competition. A rally car must inspire confidence; the Monstret inspired dread. Its unpredictable torque steer and terminal understeer made it a hazard to its driver and anyone in its path. Third, and most presciently, the writing was on the wall for the two-stroke engine. Emissions regulations, fuel economy concerns, and the simple reality of oil mixing and high consumption meant the two-stroke’s days were numbered globally.

Saab’s pivot to the Ford-sourced V4 engine for the 96 model was the final nail in the Monstret’s coffin. The V4 offered smoother, more manageable power, better reliability, and a cleaner emissions profile. The engineering resources were rightly redirected toward mastering this new architecture and, later, toward the turbocharging technology that would become Saab’s signature. The Monstret had served its purpose: it had defined the absolute ceiling of what the 93 platform could tolerate, proving that path was a dead end. Its true legacy was not in its components, but in the institutional lesson it taught: that Saab’s future lay in intelligent forced induction, not in doubling down on a fading technology with brute force.

Legacy: The Ultimate “What If” and a Blueprint for Boldness

Today, the sole surviving Monstret resides in the Saab Car Museum in Trollhättan, a silent, fiberglass-and-aluminum monument to a different era of automotive R&D. It never won a rally, never turned a wheel in anger on a competitive stage, and certainly never approached a production line. Its value is entirely symbolic. It stands as the ultimate expression of Saab’s “born from jets” mentality taken to its logical, terrifying extreme. It is proof that the company’s engineers were willing to entertain any idea, no matter how outlandish, in pursuit of a performance goal.

More importantly, the Monstret’s failure directly paved the way for Saab’s greatest successes. By conclusively proving the two-stroke’s limits and the dangers of excessive front-end mass, it cleared the conceptual runway for the turbocharged 99 and 900. The spirit of the Monstret—the refusal to accept conventional solutions—lived on in those cars. The 99 Turbo didn’t use two engines; it used one, intelligently pressurized. That innovation, born from the lessons of the Monster, defined Saab’s performance identity for two decades and created one of the most iconic dynasties in automotive history. The Monstret was not a failure of imagination, but a necessary, spectacularly volatile step in the learning process. It is the cautionary tale that made the triumphs possible, a screaming, smoking testament to the fact that sometimes, you have to build a monster to discover what a hero should be.