SKN Audi RS5 and BMW Z4

The delights of Lower Saxony

The German province of Lower Saxony, a strange setting for a day to be filled with pure joy.There’s a place called Benstorf, to be exact, and there can be found the headquarters of SKN Tuning, a firm with now twenty years of experience. By way of introduction Ralf Nissel, managing director and mastermind of the tuning concern, waxed lyrical about what they had done to optimize the two sports cars manufactured in the state of Bavaria and promised with supreme confidence that there was ultimate motoring enjoyment in store.

With its 569 Newton metres of torque the SKN roadster eats up the asphalt in almost any circumstances and constantly surprises. Photo by Peter Wagner.

A contortionist from Munich

First to be encountered, the Z4 35i RS Turbo - it doesn’t quite roll off the tongue - and the search for pure enjoyment commences. Even in the standard series model of the white folding-roof roadster with its eye-catching decals there lurks a potent 3 litre in-line six cylinder bi-turbo designed to impress. We drove to Munich with the most powerful SKN tuned version, with Stage 3 software optimization, a K&N sports air filter, a Milltek performance exhaust system, all of which combine to give 401 horsepower and 569 Newton metres of torque (Series model data compared: 306 horsepower and 400 Newton metres). As soon as we were on the Autobahn heading south it became very clear that SKN had created a true highway eater. Sure, the hundred kilometres an hour mark could be reached in under five seconds, but more noteworthy was hitting 200 after only seventeen seconds. And very impressive was the discovery that even at 2,000 RPM much of the massive torque was already available, and that the torque kept on coming smoothly and harmoniously until the peak RPMs between 6,500 and 7,000 were reached. The aplomb of the power plant even at speeds over 250 kilometres an hour was truly persuasive. It amused us that thestandard speedometer shows only markings up to 280, although the SKN version is by no means bothered by this. In our test report at the end of the day we were able to note that our top speed had been 300. And with the option of longer gear ratios at the rear axle even 310 would have been possible.

Ralf Nissel, the SKN managing director himself, programmed the individualized driving mode which opens all four flaps of the Milltek exhausts and gives a sound which is hard to forget. Photo by Peter Wagner.

The thunder of Ingolstadt

The actual speed of the Z4 we were able to check using the digital speedometer of the automobile which followed our rush downthe highway, the Audi RS5 which had also been given the radical SKN special treatment. In this case Power Level 2 was deployed, with electronic tuning, a sports air filter and also the Milltek exhaust rig, thisone with controlled flaps. Now the coupé made in Ingolstadt delivered 500 horsepower and 468 Newton metres of torque, respectively 50 and 38 more than the series model. In comparison with the SKN Z4, 100 horsepower more, but also 100 Newton metres less torque. Responsible for the disparity are the completely contradictory motorization strategies. The Audi can certainly keep up, but it cannot run away from the BMW. Yes, the Audi too can breach the 300 kph barrier and goes from zero to a hundred in four seconds if the driver is so minded. But keeping up with the Bimmer means keeping your eye on the RPMs, which need to stay close to 6,700. For it is at this point that the aspirated V8 is at its best and the optimized electronics get the maximum out of the power plant. And while the BMW demonstrates sheer power to advantage it is the Audi that sounds the most potent. When the eight cylinders come close to the magic RPMs there is a roar of triumph from the exhaust pairs, each with their oval outlets. The sound remains modest when the exhaust flaps are closed but when open, the SKN RS5 releases a thunder of the Gods. Hardly needs mentioning, but this trip alone more than fulfilled the promise of ultimate motoring enjoyment.

On the race circuit a weakness if the Z4 comes to light: Too much grip from the rear axle means significant under-steer. SKN accept this and do much to compensate with modifications which give priority to a stable and calm drive without surprises. Photo by Peter Wagner.

Like a second skin

The BMW’s stability and confidence on the road, thanks to the perfectly set suspension, is almost as impressive as its paceon the highway. Again the brilliant Bilstein B 16 coil-oversdo a great job in combination with Conti Sport Contact 5P tyres. There is good camber, and especially at the rearthe result is a super smooth drive with the chunky 265s at the back (235s at the front) with the rear end of the Z4 having superlative grip. So far, so good. Only everything that works so well on fast Autobahn curves or winding country roads shows itself from a different side when the car is taken onto a test circuit at Garching near Munich. Counter-productive grip! Here the Z4 simply has too much of it and follows orders at the velocity of cold molasses! And this leads to hefty under-steer, a phenomenon already well known with the current Z4 series models. So it´s best to head back to those winding country roads. There is the setting to appreciate the reassuring confines of the cockpit of the SKN Z4 35i RS Turbo, fitting the driver like a second skin, making him at one with the automobile. The steering is direct and allows for perfect control. The six-gear transmission implies more frequent shifting than might be thought necessary with the huge amount of torque on tap. While the sound produced by the Milltek stainless-steel exhaust system is obviously less wild (with two cylinders fewer) and cannot rival the thunder of the RS5, the roadster pilot is nevertheless serenaded with a down-and-dirty and thoroughly wicked vibrato which heightens the desire to give the 401 horsepower free rein, again and again.

On the test circuit the SKN RS5 demonstrates unexpected racing pedigree. Thanks to the Bilstein coil-overs, optimized camber and the massive 285 Pirelli tyres with Maserati rubber mix it displays fantastic grip and loves the corners. Photo by Peter Wagner.

Unexpected racing qualities

Back on the Garching test circuit there is a lot of fun to be had with the Audi. Indeed here the tuned coupé demonstrates unexpected racing pedigree. The tuner had made available as individualized MMI mode, programmed by the boss himself, which at the touch of a button adjusts steering, ESP, sports differential and other systems and, yes, opens the flaps on the exhaust pipes. Yes, this means that when pushing into a tight corner there is the realization that this Audi has a weight of not less than 1,800 kilos. But once the car is on the ideal line through the curve it simply stays there. The traction the Audi offers is indeed spectacular. Here the work done by SKN on the Audi drive train shows its benefits in impressive fashion. The Bilstein suspension which served well in the BMW also gives the Audi excellent drive characteristics. Added positive attributes are the finesse of the camber modification, the track widening of both axles and the sport differential offered by Audi as an option. All of the components function perfectly together to optimize grip, as if glue were holding the 285 rubber to the asphalt. Incidentally, the test car had Pirelli P Zeroes with a rubber mix developed specially for Maserati, according to SKN the best mixture the Italians offer. Thus it is the tyres which bring forth the final traction advantages of the Audi, advantages which make the driver loathe to abandon the test circuit. And what a surprise: Such racing character had not been expected from the RS5.

Downside: What downside?

It is hard to draw a conclusion after two exciting weeks. The SKN crew have taken both automobiles, the Z4 and the RS5 and, in spite of the totally different vehicle concepts, they have brought them as close as possible to an ideal on four wheels. The Z4 35i Turbo arouses the enthusiasm of the driver with power to spare, calm and stable behavior on the road and also perfectly acceptable fuel consumption data - depending on driving style between 9 and 13.5 litres. The RS5 beguiles withits high-revving V8 power plant. It demands close control, but when allowed to go to the top of the range it has amazing bite. The sound made by the all-wheel-drive auto is nothing short of phenomenal and, with the flaps open at the back, the full throated roar is unrivalled. There is, however, the fact that the visit to the service station will reveal a thirst for 15 litres per hundred driven.

Bilstein, BBS, sports exhaust; These are the classic areas for tuning and here the end result is visually successful. SKN versions are exe-catching without being gaudy. And both cars remain easy to handle. Photo by Peter Wagner.

There is not much difference in comfort between the two sporty speedsters (largely thanks to the Bilstein coil-overs in both) and there is little to choose between them in everyday driving situations. Nor are the SKN modifications unduly expensive: The tuning of the Z4, including exhaust system and air filter will cost 3,998 Euros: Getting 500 horsepower from an RS5 costs 4,958 Euros (including exhaust system with controlled flaps at 2,899 Euros and air filters at 89 Euros each). Downsides?Hardly any worth mentioning. And that is surely a feather in the cap of the combined forces from Lower Saxony and Bavaria.