The 989 prototype illustrates how Porsche envisioned a 911-like sedan in 1988

In the 1980s, a new breed of high-performance sedans emerged letting speed-hungry motorists take all-you-can-eat turns at the horsepower counter. Porsche wanted a slice of the pie, and strong 928 sales encouraged it to look into adding a more spacious model to its range. Called 989, its answer to the BMW M5 was a 911-like sedan it spent over three years developing before consigning to the automotive attic. Here’s what could have been.

Porsche planned to take on BMW and Mercedes-Benz, but it insisted on forging its own path to the luxury sedan segment. Starting with a blank sheet of paper in 1988, its stylists penned a shapely four-door with a long front end characterized by headlights positioned nearly horizontally, wrap-around turn signals, and the complete lack of a grille. Its roof line sloped like a 911’s into a rear end with pronounced wheel arches and individual lights relatively close to the 928’s. Inside, the 989 received Porsche’s familiar analog instrument cluster and four seats.

Although the 911 clearly inspired the 989’s exterior design, the two models shared very little under the sheet metal. Porsche knew it needed to bring a front-engined, rear-wheel drive sedan to the market in order to be competitive. Sticking to the 911’s time-tested rear-engined layout would have put it in the same segment as Tatra, which wasn’t what executives were aiming for. Using an air-cooled flat-six was quickly ruled out, too.

Instead, the 989 received a front-mounted, water-cooled 4.2-liter V8 engine related (but not identical) to the eight-cylinder that powered some of Audi’s bigger models during the 1990s. It developed 350 horsepower in its most basic state of tune, which was a lot back then. For context, the 911 Carrera received a 214-horsepower, 3.2-liter flat-six in 1988, while the 911 Turbo put 282 horses under the driver’s right foot. 350 eclipsed even the vaunted BMW M5.

Porsche was completely serious about putting the 989 in showrooms; the sedan wasn’t an experimental design study built to turn heads on the auto show circuit before spending years in a warehouse. As one team fine-tuned the chassis, and another tweaked the design, intrepid road testers began putting the V8 through its paces in a modified Mercedes-Benz W124 test mule (shown in our gallery). This model was chosen for a couple of reasons. First, Porsche’s engineers were familiar with it because they were in the process of helping create the formidable, 322-horsepower 500E. Second, it was very close to the 989 in terms of size, weight, and performance, and its engine bay was big enough to effortlessly put a V8 in. The same couldn’t be said about a BMW E30.

Development work progressed under the watchful eye of Ulrich Bez, the company’s head of development, and executives locked in a 1995 release date. All was not well in Stuttgart, however. Porsche sales (and, consequently, profits) started falling in the late 1980s and fixing its problems became alarmingly urgent in the early 1990s. Some rumors claimed the company was on the brink of bankruptcy; others speculated it would get scooped up by Daimler. Meanwhile, the 989 project was costing far more than anyone had anticipated.

The numbers didn’t add up. The 989 was on track to become a huge loss-maker for a company that needed a massive hit. Porsche canceled it in 1991, and Bez left for Daewoo shortly after; he later ran Aston Martin.

Some of the sedan’s key styling cues resurfaced on the 993- and 996-generation 911s released during the 1990s, but Porsche abandoned the idea of planting its flag in the luxury sedan segment until it launched the original Panamera in 2009. As for the 989’s V8, it very nearly lived on as a replacement for the 911’s aging air-cooled flat-six but the ax fell on those plans, too, and it remained at the prototype stage.

In hindsight, Porsche didn’t need a sedan at the time. It needed to go back to its roots. The first-generation Boxster introduced as a concept at the 1993 Detroit auto show and launched three years later saved the brand. Interestingly, Porsche developed an entry-level roadster during the 1980s but it canceled that model, too. Had the 989 been launched, and had it sold well, you could be picking up a 989 you found on Craigslist this weekend. Instead, you may be waiting a few more years for a Panamera.