It is common knowledge that Porsche has had a hand in a number of high performance machines sporting a different badge, these being two of the most exciting.

Early 1990s, and the Deutschmarks aren't exactly what you could call flowing freely. In fact, things are looking pretty glum for Porsche. Its model line-up could hardly be described as sparkling - ageing 944 and 928, and a further evolution of the 911, were filtering out of showrooms in these post recession times. But hat was before the neighbours, Mercedes- Benz, popped round for a friendly chat.
Having set itself a global plan of launching one new model every year, Mercedes had backed itself into a corner with its mid-sized E-Class saloon (which was well into its production programme). While BMW was enjoying the success of its formidable M5 super saloon, and Vauxhall was fending off the enraged tones of Daily Mail readers with the Lotus Carlton, Mercedes was being left behind in the autobahn storming, super saloon market.

With R&D departments already stretched, Mere execs made the call to their sports car neighbours to ask if they could take on the production of their E-Class super saloon. With the now defunct 959 production line sitting idle at Zuffenhausen, Porsche bosses accepted the task with open arms and set about building the first four-door Porsche saloon.

Although Porsche had no hand in the 500E's development, it was entrusted with the task of making everything Mercedes had lined up for the 500E fit into the W124 bodyshell. First task was to make the 5.0-litre, quad-cam V8 fit into the engine bay, which meant the engine bay needed widening and reinforcing, not only to the bay area, but the floor of the car, too. While it was at it, Porsche also insured the motor could be placed as far back in the engine bay as possible to aid the car's handling. Porsche engineers alsohad to beef up and re-engineer the 500E's rear suspension, widen the transmission tunnel and redistribute the car's new exhaust system. The Mercedes wider front and rear arches were also attached while at Porsche, before returning to the Mercedes plant for painting before heading back to Porsche for final assembly. Complicated? Sure sounds like it.

With Porsche literally employed solely to assemble the 500E, it comes as no surprise to hear that the car's specification is, on paper at least, a little disappointing. Not that 326bhp and 354lb/ft torque are to be sniffed at, but when hooked up a four-speed automatic transmission (no manual was available), and Anti-Skid Control that couldn't be completely switched off, the Porsche-built 500E was going to have its work cut out convincing M5 and Lotus Carlton drivers that it was much more than just a fast taxi. Albeit a bloody fast one. In stark contrast, Audi's RS2 couldn't have been built by anyone other than Porsche.
Again Audi had its hands full with its range of saloon cars, and turned to Porsche to develop and build a wilder variant of its S2 quattro coupe. And develop it, it did. Taking the five-cylinder, turbocharged engine from the S2, Porsche swapped the pair of camshafts to produce greater gas flow and fitted a bigger KKK turbocharger and intercooler. Boost pressure was also raised to a heady 20psi. The exhaust system was also modified for improved airflow, and the engine's electronic brain was reprogrammed to provide the required volumes of fuel and air, and be able to run on 98 Octane fuel. The results were a mighty 315bhp produced at 6500rpm and a hefty 302lb/ft of torque at 3000rpm.

Dipping into its own parts bin, Porsche elected to fit the RS2 with a set of its own brakes - ventilated discs front and rear, four- pot calipers and ABS, giving the RS2 the stopping power to match its performance. Other performance car features of the RS2 included a six-speed manual gearbox, five- spoke, 17-inch Porsche Cup alloys and an estate car bodyshell with a suitable number of scoops, ducts and spoilers to distinguish it from anything else you would find in the 1995 Audi brochure.

Arriving at the Norfolk base of left-hand drive specialist MCP Motorsport snapper Fraser and I fail to acknowledge the flint grey 500E parked at the entrance, though this is hardly surprising when a canary yellow RS2 is shining brighter than a piece of burning magnesium.

Get past the wraparound rear reflector, bulging arches and Cup alloys, and the RS2's interior is just as inviting for the enthusiast. Figure-hugging Recaros, perfectly sized three-spoke leather wheel and white-faced dials (including a set of three auxiliary dials, displaying oil temperature, pressure and battery vaults) provide a perfect ambience for a serious cross-country blast.

Fire the RS2's five-cylinder engine into life, and you are greeted with the most tremendous, bassy warble as those in-line cylinders burst into life. Being a left-hand drive example (180 out of the 2200 produced were right-hand drive), the pedals feel perfectly spaced, and as we venture out of the dozy seaside town of Sheringham, the RS2 feels as easy to pilot around the dithering pensioners as the Ford Focus we arrived in did. Away from the town, and with the fluids warmed through and gauges all pointing at their optimum operating temperatures, it's time to flex the right foot and experience this pseudo-Porsche's much talked about performance.

Well, come on then... If you've driven an early 911 Turbo you would have first-hand experience of that old favourite turbo lag. But the RS2 takes the biscuit. Below 3000rpm you can forget it; at 3500rpm things start getting interesting; hit 4000rpm, prepare for take-off. On full boost the RS2 delivers the motoring equivalent of being fired from a cannon. Only the bulky gear change hampers performance, but get it right and 60mph will arrive 4.8 seconds after you started, l00mph after 13.1 seconds and the chase for the horizon won't level off until it's reached 163mph. Not bad for an estate car!

It's not all about straight line speed, either, because the RS2 can handle itself when the road turns challenging. Admittedly, the steering fails to deliver the levels of feedback preferred at these kind of speeds, but it doesn't stop you from guiding the RS2 with an impressive level of precision.
Grip from the 245/50 ZR17-inch tyres is vice-like, and combined with the Audi's unflappable Quattro all-wheel drive system, loss of traction is not an issue. Hell, it even has an unexpected level of fine tuning that allows for a degree of adjustment when you've arrived too fast at the apex.

Only the RS2's overly stiff ride (well, how else do you get an estate car to handle so well?) blots its otherwise faultless copybook. Jarring over potholes, and vibrating over cats-eyes, the RS2's build quality has its work cut out.

Stepping into the 500E after the RS2 is a real chalk and cheese affair. Visually, the 500E is only truly appreciated when its wider front and rear arches can be fully taken in (from a low down, head-on view), and that's it. For the whole car. The interior is generously appointed with electrically adjustable leather seats, slabs of wood and very few bells or whistles. And, of course, an auto gearshift.
In contrast with the Audi, the Mercedes' 5.0- litre V8 is barely audible on tick-over, and only a flash of revs to accompany a prod of the throttle confirms she's running. As soon as you select 'D' it is immediately apparent the 500E is going to serve up an entirely different course to the Audi.

Silent, simple and effortless to cruise in, initial reactions to the big Benz are disappointing: "It's too big, the auto 'box doesn't kick down quick enough, and are you sure Porsche had a hand in this?" expresses features editor Holtam, who's helping out with our photoshoot. After a couple of miles, I'm also beginning to wonder whether the 500E is the super saloon I read about as an impressionable teenager.
The 500E is different kettle offish to anything you've driven before. More refined than BMW's then M5, and from a different plant to the Lotus Carlton, the Mercedes is about travelling serious distances, at a serious pace, in sumptuous comfort. Squeeze the loud pedal into the carpet, wait for the four-speed auto to drop a cog or two, and the 500E comes to life.

That big V8 shoves you along on an addictive combination of power and torque, powering this four-door saloon to 60mph in a smidge over 6.0 seconds, l00mph in 14.5 and onto a limited 155mph. It takes a pretty ruthless style to tap into the car's performance, but once you've tasted it you can't help but go back for more.

Dynamically, the Mercedes is less enthralling. Competent, but lacking in any flair, the 500E's chassis is capable with dealing with most scenarios you can throw at it. The steering is far from what you could term razor sharp, but it's quick, weights up nicely and gets the nose turned in precisely. Same goes for the car's handling, which far from being limpit-like, body roll is kept to a minimum (thanks in part to the self-levelling rear suspension), grip levels feel unbreakable, and its eagerness to hold, or adjust its line is impressive for a car of its size and bulk. It may be no sprinter, but it's one hell of a thoroughbred.

Are the 500E and RS2 worthy of their Porsche connections? With the Audi there is no question of its pedigree. Designed and built by Stuttgart's finest, the RS2 was sensational when it was new, and still is today, and even succeeded in overshadowing its 21st Century cousin, the RS4. And what of the 500E? With less involvement in its development from Porsche, it's understandable that it feels more like a big Benz than it does a Porsche, but consider this. When the 500E was new, there wasn't a Formula 1 driver worth his Nomex overalls who would consider anything but a 500E to get from one European Grand Prix to another, and that today, the fortunate few who race historical Fl cars have also taken a fancy to the Merc. There is a little more to the 500E than perhaps originally meets the eye '