标题: [转帖] Audi A4 DTM racer - a closer look [13P] [打印本页] 作者: zdxx520 时间: 2010-2-4 22:52 标题: Audi A4 DTM racer - a closer look [13P]
They call them front-engined F1 cars. They are the DTMs, the most advanced touring cars ever built, and Audi's A4 is the most advanced of the bunch. But we mainly like it because it has loads of wings and AeroMentalStuff...
This is what all racing cars should look like. In fact, it's what all cars should look like.
Deutsche Tourenwagen-Masters - you can see why the DTM acronym took off - might be operating in slightly reduced circumstances at the moment, but it's still easily the world's best saloon car championship. The racing's intense, and there are some interesting personalities involved - apart from Ralf Schumacher, obviously - but really it's all about the cars. They're so cartoonishly extreme they could have been drawn by Warner Bros maestro Tex Avery. Is there a better aero device than the cascade of wings around the wheelarches of an A4 DTM?
Of course, we love touring cars because they're based on the more mundane things we drive every day. We love the fact that there's a regular Audi A4 underneath this monster. But there isn't really. I drove one of these once, and I can tell you that it had as much in common with the standard car as my bank balance does with Simon Cowell's. But that doesn't mean we can't just stare at it. For a week or two.
Despite the presence of four doors and what looks like a boot, this is pretty much a single-seater in drag. The regulations have barely changed over the past few years, and DTM is meant to deliver the maximum spectacle for the fans with, if not minimum, then at least predictable outlay for the teams involved. But this doesn't make DTM the province of some German-accented hillbillies. The chassis consists of a tubular spaceframe, with a carbon-fibre composite safety cell integrated within it. The front and rear crash structures are also carbon-fibre, so although smashes are routinely explosive, the driver is extremely well-protected.
The engine is a dry-sumped, normally aspirated 4.0-litre V8, equipped with mandatory intake air restrictors, and makes 460bhp and 370lb ft of torque. It's mounted some distance behind the front axle, which in turn means the centrally mounted driver's seat is located in the middle of what would be the rear bench in a stock A4. (It really is the weirdest thing to sit in, but I'll come back to that.) The transmission is a beefy six-speed sequential, harnessed to a triple-plate carbon-fibre clutch. Steering is by servo-assisted rack and pinion, and there's double-wishbone suspension front and rear, using a pushrod spring and damper unit and adjustable gas-pressurised dampers
In other words, this is a sophisticated racing car, arguably a lot closer to endurance prototypes than straight touring cars. It's also a major prong of a phenomenally successful motorsport campaign that has seen Audi amass 25 DTM victories since returning with a factory effort in 2004 (the year a saloon-based formula was adopted. There had been Audi TT privateers before that). In tandem with the countless wins racked up by the R8, R10 and R15 at Le Mans and beyond since '99, you'd have to say that the only thing Audi hasn't nailed in its motorsport career is F1. Rumours of which refuse to go away...
The car you see here is known internally as the R14 Plus, the sixth generation of the A4 DTM. Improving such a successful car in a championship with so little wriggle room is an odd challenge in top-level motorsport, but then there is a recession on
"Basically, in the sixth year of continuous development, the potential of any engine design has been fully exploited," explains Ulrich Baretzky, the man in charge of this area within Audi Sport. "The most clearly visible modification when the bonnet is open is the air box on top of the engine," he continues. There's a new intake plenum, and the car's improved breathing has apparently benefited its overall driveability. Racing drivers like that sort of thing.
But the biggest gains have been made in its aerodynamics. Audi Sport technical director Dr Martin Muhlmeier is the poor soul tasked with explaining Audi's computational fluid dynamics processes down the phone to me from Ingolstadt.
"The work we do between the end of one season and the start of the next is absolutely critical," he says, speaking v-e-r-y s-l-o-w-l-y, "because the design of the diffuser and main body parts is frozen at the start of the year. DTM is very limited compared to F1, so we have to examine the regulations very carefully to find the areas of potential. I'll give you an example. We have scope for development in the area between the ground and 275mm above the ground, which is roughly where the doors stop. In other words, we can work on the underbody and the floor..."
Most of the focus, then, is on aero and air flow. Muhlmeier talks about Audi's ‘closed loop' process that sees the CFD boffins identify new approaches, before trying them out on wind-tunnel models. After that, the resulting data is fed back to the boffins, who then feed it back into the system and start all over again. Imagine all those algorithms.
The result is a fabulous blend of the empirical and the abstract. The rear end of the R14 Plus really does deserve a place in the Tate Modern. For 2009, the eureka moment involved mounting the rear wing from the top rather than below, improving its flow characteristics. The front wheelarch winglets, meanwhile, are adjustable. On a fast circuit like Nuremburg's Norisring - two big straights, basically - they're closed or removed altogether, to reduce drag and boost top speed. But on the big downforce tracks - everywhere else - they're open.
Steps were also taken to improve the car's dynamic behaviour relative to a couple of highly significant and particularly variable, er, variables: deteriorating tyres and lessening mass as the fuel tank emptied. Then there's the braking system. Though AP Racing supplies a ‘control' braking set-up for every DTM car, improving air flow through the calipers clearly helps consistency of performance.
"The most important thing," Muhlmeier says, "is that all the components in the car are balanced and robust - engine, suspension, aero, the set-up. The driveability on our car is pretty good."
Hmm. That word again. So just how driveable is an A4 DTM?
"Not too tricky," says Muhlmeier, who, by the way, pointedly refuses to answer the big F1 question, "but not much like a classic, steel-bodied touring car, either. It's much more agile. Its dynamic behaviour is much closer to a single-seater. But you must still remember the difference in weight. A DTM car weighs 1,050kg including the driver, and has 460bhp. An F1 car, for example, weighs almost half that and has almost twice as much power. An F1 car can also pull cornering loads of up to 5g. A DTM car pulls between 2 and 2.5g..."
Easy, then. Or perhaps not. Over to eight-times Le Mans winner and seasoned A4 DTM pilot, Tom Kristensen. "You're always sliding the car, pushing it," he says, "whereas in a prototype, if you're sliding you're in bad shape. As a driver, you're more aware of the overall balance [in a DTM car] than the sheer speed.
If you've never set foot in a DTM car before, the thing you're most aware of is how alien it feels, even if you have previous experience of racing cars. The saloon silhouette body fools you into expecting something trad inside. But the central driving position is anything but; there's actually a disturbing element of rocketry to it. You sit so low and so far back. In a race situation, everything needs to be exactly where it should be, so as random as it initially looks, it's all entirely logical. The buttons, switches and instruments are the usual race-car stuff - main digital display for gearshift lights, rev counter, lap timer, radio and pitlane operation, lights etc. A paddle to the right of the wheel triggers brake calliper cooling, and you can also adjust the brake balance.
Just like this car, the A4 DTM I drove a few years back also had a ‘Start Fuck-up' switch. I think it was Kristensen's car, and evident proof of his bone-dry Danish sense of humour. After three race wins, seven pole positions and 16 podium finishes, he's quitting DTM to focus on sports-car racing for 2010, clearly targeting a ninth Le Mans win. His works drive has been given to former British F3 hotshoe, 26-year-old Oliver Jarvis, one of many Brits currently competing in the German touring car championship. And another reason not to miss it 作者: 紫色槟榔 时间: 2010-2-10 16:06
