The mystery Merc you’ve never heard of

Just 30 examples of the Mercedes-badged Isdera Imperator were built

Here at C&SC, we routinely drive rare cars that garner stares. It’s just part of the routine.

There’s nothing routine about this machine, though: despite the traffic-stopping looks and striking, blunt-wedge styling, it’s so rare that even among motoring enthusiasts it can go unrecognised.

What is it? An Isdera Imperator 108i – a Mercedes-powered supercar constructed to high spec in tiny numbers. Just 30, to be exact, and you’ll probably never see one on the road.

Here’s this mysterious machine’s story, from CW311 concept to 330bhp reality.

Child of the ’60s

In 1969, Mercedes started building an experimental prototype fitted with a Wankel engine and wrapped in a glassfibre body.

It was labelled C111 and the first-generation model was soon upgraded with a four-rotor power unit good for 370bhp and genuine supercar pace.

Not for sale

Next, the Stuttgart marque started installing diesels in its test machine, smashing records yet steadfastly ignoring calls to put it into production.

Demand increased further when the firm added a 5-litre, twin-turbo V8 to the wind-cheating design, while a visual step-change followed with the even more powerful C112 in 1991.

Non-production alternative

This last six-litre V12-powered prospect was particularly tantalising, because Mercedes actually took hundreds of deposits for production models, only to shelve the project.

This left the super-rich with only one way to turn: the Isdera Imperator – a similar car that was a Mercedes in all but name.

What copyright?

Designer Eberhard Schulz had started working on his homage to the C111 prototype in 1972.

In doing so, he unashamedly adopted several trademark features of the Mercedes 300SL Gullwing and 300SLR – including the doors, sidepipes and vents.

CW311 über alles

Schulz partnered with tuning house BB and together they created the CW311, the name reflecting its inspiration and promoting its alleged drag coefficient.

The project used entirely German parts – mostly from Porsche and Mercedes – and generated huge press when it was unveiled in 1978 as spiritual successor to the experimental Merc prototypes.

Plenty of grunt

Using an AMG-tuned 6.8-litre engine, the CW311 was an instant star and topped out at just shy of 200mph.

With its shape, power, eye-catching periscope mirror and pioneering pearlescent white paint, it’s little surprise that the CW311 proved such a draw.

Independent Isdera

Gimmicks and gizmos aside, though, it was a long way off being the car that Schulz dreamed of presenting to the public, not least because many of its features would be horribly impractical in the real world.

So Schulz parted ways with BB and, in 1982, formally established Isdera.

Reborn and roadworthy

Two years later, he showed the Isdera Imperator 108i at the Geneva Salon – and it was quite conspicuously a road-ready version of the CW311, with its wheelbase extended by 8cm and rebranded as a usable GT.

Low numbers special

With Isdera, boutique was an understatement: each car was hand-built and tailor-made.

With no official figures to go on, it’s believed that only 30 Imperators were ever made – paid for up-front – with just three of the first 17 built for export.

Second series

The only major change in the Imperator’s production life came in ’91, with the arrival of a new iteration primarily created to meet emissions controls.

The upgrade also included ABS, drop-down headlamp covers, improved aerodynamics and side-exit exhausts plus, towards the end, uprated brakes and bigger wheels.

Two of a kind

For our photoshoot we brought two Imperators together in the UK for possibly the first – and likely the last – time.

The red car is number 17, the last of the first generation in terms of styling and the first of the second generation in that it carries the 5-litre V8. It is also the only UK-market example, which explains the door mirrors.

The later, silver car is also powered by the V8 and was one of two second-series models to go to Japan from a production run of 13.

Same but different

Considering that they look identical at first sight, the two are actually very different.

Both have clean, uncluttered lines and a spaceship-like appearance, but the later vehicle in many ways looks closer to the original CW311 concept, thanks to those sexy sidepipes and drop-down headlamp covers.

Practical performance

But it’s not all about aesthetics: in the supercar-hungry world of the late-’80s, where the likes of the 959 and F40 were king, the Isdera – which competed on price – needed to do a lot more than just look the part.

According to the owner of the first series Imperator, “it’s surprisingly practical, but takes a bit of getting used to. It really comes into its own...as a high-speed GT. It is happy cruising at 140mph all day long.”

Reliable on the autobahn

In fact, “after the car’s recommission at the factory, the test drive included an autobahn blast at 175mph. Everything was deemed to be ‘very satisfactory’.”

The mere thought of such speeds in something so bespoke would usually be terrifying, but even today the Imperator actually feels very strong and solid.

Easy to use

Despite feeling heavy at first, the clutch is usably light, while the turning circle is excellent for a performance car and considerably smaller than those of its period rivals.

The brakes are excellent in both cars, too, while the heavy ZF transaxle is superb on the move with a forceful hand behind it, just as it is in so many cars – from the BMW M1 to the GT40.

Power on tap

Both cars gain speed with electrifying pace, punching the 5800rpm redline (6300rpm in the S2) as they effortlessly hoover up the horizon in a series of rapid lunges.

The later car does feel fractionally more civilised, but also less exciting: the five-litre lump woofles aggressively on the S1, whereas it can hardly be heard in the silver S2.

Lots of rubber

With such great power comes great responsibility, but the low-volume Isdera doesn’t let itself down when it comes to the safety side of things.

Ignoring the woeful side and rear visibility, cornering is pleasingly neutral, handling assured and traction unassailable – in large part thanks to Countach-sized tyres which spread the power across the asphalt at the rear.

Thrill, don't kill

And, despite the wind noise and the realisation that the aircon is as essential to your survival as water, the Isdera is far from harrowing.

The ride is superb and the engine wonderfully flexible, while the driver is kept comfortable in a cloth-covered Recaro seat. This is definitely not one of those supercars that thrill you and threaten to kill you in equal measure.

Mercedes mystery

In fact, the Imperator by and large feels like a proper car properly built – not just some Merc-powered pastiche.

What of the truth behind that Mercedes connection? For decades, people have assumed that the project had the approval and backing of the Stuttgart giant, a view supported by the lack of controversy surrounding the badging.

Star power, without permission

Today, though, Daimler is eager to dispel the myth: "The CW 311 was not made by Mercedes-Benz and is – due to that fact – no Mercedes-Benz. The three-pointed star was put on the car without permission. Eberhard Schulz never worked for Daimler, the CW311 is not on display in the Mercedes-Benz Museum and our archives have no documents or pictures of the car."

Shed-built winner

That makes sense, given that it would be odd for Daimler to sanction a car packed with Porsche engineering. To some, that might take a bit of the sheen off the Isdera, but to others it will just increase the mystique.

The fact that this was one man’s work, that the prototype really was built in his spare time over six years and that each production car was then created from scratch by a team of just 12 (and all without any factory support or backing), only makes the mysterious Imperator more impressive.