Porsche's manufacturing complex lies in the northern suburbs of Stuttgart, and deep within its keep is the Rössle Bau factory. It's the birthplace of the 959—if Porsche needed a throne room for a royal seat forged of aluminum and steel, it would be here.

Many a twin-turbocharged flat-six marched through these gates, but there were also off-badge dalliances: Porsche produced offspring that would never carry their progenitor's highborn surname.

Here are two forgotten children of Stuttgart, perhaps not Porsches in name, but legitimate powerhouses nonetheless.

1990-1995 Mercedes-Benz 500E

The famously bulletproof W124 Mercedes sedan was a handsome car that radiated a timeless quality. And then Porsche got its hands on it.

The 959 assembly line sat idle after the final 1989 production run. Financial times were tight and new-model Porsches gathered dust in showrooms. In contrast, Mercedes-Benz R&D was tapped-out, busy with new model launches on the horizon. Porsche's bored eyes lingered on Mercedes' blooming order sheets, and a fleeting partnership was formed.

While Benz called the shots on what it wanted the 500E to be, it was Porsche that made it special. Cars would leave Mercedes-Benz to spend time at Rössle Bau, where Porsche massaged the flanks to allow widened 16-inch alloys, installed an all-aluminum, five-liter V8 under hood, and fitted a reinforced rear suspension. Then, these cars would be sent back to the M-B shop for paintwork. Following that, each 500E would return to Zuffenhausen for further final assembly.

After 18 days of being shuttled between parents like a kid in a custody battle, you might expect the 500E to be a little confused—all the more impressive then, this behemoth's singularity of purpose. The 500E is kicked down the road with the relentless prodding of 326 normally-aspirated horsepower, while four passengers fit within the confines of well-bolstered, leather-trimmed Recaros.

With a four-speed automatic transmission and ample amounts of wood and leather dressing up the cabin, the 500E was never going to be a ballet dancer. Zero to 60 came in around six seconds, and the quarter passed in the mid-14s. It was quick for its day, yet not an especially good drag-racer. Line-up that three-pointed targeting reticule with the horizon and pull the trigger, however, and the 500E's raison d'être becomes clear.

Porsche essentially took the bank-vault ideal of the W124 and turned it into an ICBM: Delimited, 500Es could reportedly crack170 mph.

Around 1500 cars made it into the U.S. from 1992-1994, each one easily identifiable by its race-car-aping flared front fenders. Total production was bookended from a small number of cars built in 1990 to a final few in 1995, available only at special customer behest.

1994-1995 Audi RS2

It seems that "Audi" has always been synonymous with "hair-trigger war-wagons," the best of which it no longer bothers to bring over here.

Were you in the market for a sure-footed cargo-hauler in the early Nineties? The Audi option was a modestly powered wagon with insipid handling and ho-hum styling. It didn't bring that one stateside either, but enthusiasts shed not a single tear.

Torrential wailing would result from the Europe-only status of what might well be considered the ultimate road-going Audi of its era. While the homologation-special Sport Quattro set imaginations ablaze with its easily recognizable stubby, flared shape and rally-stage exploits, the Audi RS2 is still less well-known. But show any Audi enthusiast an intake manifold with "Porsche" scripted on it, squeezed into the middle of a bright-blue engine bay, and hyperventilation will ensue.

Based on the humble B4 chassis that would underpin underwhelming Volkswagen Passats, this Rennsport-badged wagon is an odd mix of its parental DNA. From Audi, we get the sure-footed quattro system and characteristically grumbly straight-five motor. To this, Porsche added its expertise in turbocharged trickery, fitting a larger KKK compressor and tweaking camshafts to pass gases through the head at a greater rate. Boost pressure was raised to a hyperbaric 20 psi with uprated injectors, intercooler, and ECU tuning to match.

Sitting low on deep-dish alloys, even a non-gearhead knows something's up. Why, for instance, does a wagon need to wear the same shoes as a 964 911 Turbo? Other fangs peek through the sheep's clothing, too: Surely, those are 911 wing-mirrors; and that's no factory air dam.

Resemblance goes deeper than cosmetic features. Along with 911 turn signals, the RS2 has the brake package off a 968 Club Sport. The turbo lag from the big compressor is also a Porsche "feature": below 3000 rpm, nothing; around 3500 rpm, a minor stirring; above 4000 rpm, we've jumped to plaid!

Unlike the 911, however, there's no slip and scrabble, merely the physics-defying grip of a startled cat going up a curtain.

With a six-speed manual the only option, getting the RS2 off the line requires a bit of finesse. Get it right, though, and the results are stupendous. This 315-hp, 3500-lb wagon puts out homologation-special 0-60 figures of around 4.8 seconds. Even more impressive is the holeshot: The RS2's 0-30-mph time of 1.5 seconds put it ahead of immortals like the McLaren F1.

This content is created and maintained by a third party, and imported onto this page to help users provide their email addresses. You may be able to find more information about this and similar content at piano.io