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4T : Reviews & Road Tests

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15 March 2011


It’s just 48 hours ahead of the Geneva Motor Show and I’m a bit punchy, having just experienced a whirlwind tour that included the Audi Lightweight Design Center (ALDC) in Neckarsulm followed by a quick trip to Lamborghini headquarters to take in one very impressive new lightweight development center with a focus on carbon composites as well as much of the production line of the all-new and seemingly all-carbon Lamborghini Aventador. To say there is a lot for my jet-lagged brain to process is just a bit of an understatement but for now the conversation over some hardly lightweight pasta on the shore of Lake Lugano, Switzerland has those around the table focusing on one particular subject of the two-day crash course in lightweight production.



That subject is a rather unassuming Audi A5 coupe that outwardly may look like nothing more than a slightly modified S5, but internally it is known around the halls of quattro GmbH simply as “the Beast”. You see, this rather unassuming coupe is a drivetrain mule built ahead of last fall’s quattro Concept. Back then its mission was to prove the idea of the quattro Concept to Audi brass and to achieve this engineers had to come as close as possible to the lightweight construction they sought to showcase on the Paris show stand. For that they turned to an A5 already in Audi’s fleet of experimental test mules.





In fact, I think I’ve driven this car before. Back then it was a rather pedestrian-looking A5 Audi had brought out to Bosch’s test facility in Boxberg for a previous lightweight TechDay. At the time it was powered by a 2.0T and we’d been told the car was built on an aluminum chassis. I’d assumed that meant a full-on ASF (Audi Space Frame) as I then understood it. Because I’d driven it and heard the brief, I was beginning to think I was the resident expert around a table of journalists from weighty titles like Car & Driver, Motor Trend and Road & Track.



Playing the know-it-all around this sort of company should have normally been the cue for my internal Jiminy Cricket to start chirping, reminding me to shut my trap. Like I said, I was punchy. The wine was also free-flowing and the aforementioned pasta sublime. I plowed on, knocking Jiminy out of his spats and playing the part of professor when it came to the very experimental chassis of that alloy A5.



It didn’t take long before I realized I was in over my head. I’m not an engineer but others at the table were, like Road & Track’s Shaun Bailey. Bailey was intrigued by the car or more specifically just how Audi had constructed it. My recollection of the conversation is obviously not exact but a less than stellar portion went a little something like this.



Shaun: “How did they build a chassis entirely of aluminum?”



Professor Yours Truly: “Don’t know.”



Shaun: “The A8’s space frame construction is made up of a lot of specific extrusions and stampings. You can’t just produce those… not for four cars. You’d need a lot of tooling. How or why would they do so to build just four examples of a current (steel) car?”



Me, demoted to failing student: “Don’t know.”



Jiminy’s chirp finally went audible and I turned my focus to the pasta.





Two days later I’m on the Audi stand following their presentation of the A3 concept and Bailey’s questions are still nagging at me. When I drove that A5 in ’09, all I knew of aluminum was Ingolstadt’s proficiency with its aluminum Audi Space Frame (ASF). I assumed Audi could do anything. If Rupert Stadler said he wanted an aluminum A5, Michael Dick snapped his fingers and the Audi board had an alloy coupe with which to hoon. As Shaun rightly noted, it’s not that simple… and then it hit me.



72 hours earlier, not long after I first drove “the Beast”, we found ourselves in Audi’s lightweight development center. Showing how steel components could be replaced by lightweight aluminum, lighter magnesium or lightest carbon fiber was both on the agenda and on display within the walls of the Audi factory. Experimental components such as cast magnesium strut caps or various hybrid aluminum/steel Q5 B-pillars showed quite practically how Audi aims to significantly drop weight from its product range. And, it was one display in particular that caught our attention.



Maybe it was because the thing was partially covered by a shroud or maybe it was because it was just barely seen in the approved photo sets Audi had provided, but a bare chassis about the size of an A4 referred to as “MLB-Evo” immediately grabbed our attention.





As you may recall, MLB is the modular longitudinal architecture set into motion by Martin Winterkorn during his tenure at the helm of Audi. Flexible in both size and material, MLB has now been employed for everything from the predominantly steel A4 to the much larger aluminum space frame A8. And, as the name suggests, MLB is about to evolve.



As the presentation revealed, Audi is placing an incredible amount of resources in its lightweight construction research and has even dubbed the project “ultra” much like the term “e-tron” has been affixed to its electric mobility projects. Using computer modeling, Audi is targeting every point in the car’s architecture and best determining whether to use high-strength steel, aluminum (cast, extruded or otherwise), cast magnesium or carbon-fiber reinforced plastic (CFRP) to optimize maximum crashworthiness and minimum weight. The savings are significant too. Audi boasted that more than 881 lbs (400 kg) would be saved on the next-generation Q7 when it migrates to MLB in the next go-around.





The MLB-Evo chassis on hand was that of a roughly A4-sized 4-door sedan, and while it made extensive use of aluminum it looked like no previous ASF we’d seen to date. Audi has been busy working on its joining technologies, including things like self-tapping screws, flow drill screws, friction element welding and punch riveting that allow materials such as aluminum, steel or CFRPs to be rigidly joined while layers of adhesive eliminate risks of corrosion. As a result, and as you can see from the very few approved photos of the MLB-Evo chassis on display, this means a dizzying and almost patchwork mix of materials seemingly riveted together. It’s not exactly the artistic sculpted look of an A8’s space frame, but it’s actually lighter, likely safer and probably more cost-effective to build in series production.



That’s when it hit me, right there on Audi’s Geneva stand. Journalists and photographers were all jockeying to get closer to the just-revealed A3 Concept but my brain had jumped from the concept back to that MLB-Evo chassis and the quattro Concept A5 drivetrain mule I’d driven. It all made sense. Audi’s experimental lightweight A5 2.5T mule was likely a very early prototype of a drivable MLB-Evo.





Fortunately, it pays to have such epiphanies during the moments following a major reveal at an equally major auto show. Every Audi executive one might imagine was on stage or nearby answering questions thrown at him or her by press… albeit all they probably wanted to talk about was the new A3 Concept. I looked around the crowd for a target who might be able to confirm my hypothesis.



Nearby was a highly placed contact from Audi AG. After chatting a bit about the lightweight Tech Day and marveling over the A5 2.5T drive and the MLB-Evo on display, I expressed Shaun Bailey’s skepticism and drew the line between the shrounded chassis on display and the car I drove. “Seems like that’d be hard to do with your typical aluminum space frame for just a few A5s,” I commented and continued. “Is that car basically an MLB-Evo.”



“Essentially yes,” was his response, along with a broad smile.





When you think about it, it all makes sense. With modular platforms like MLB Audi and its Volkswagen Group parent have isolated a platform down to shared components in order to bring down cost, maximize the number of body styles and allow for movement across the range of key technologies. MLB-Evo seems to go one step further by separating even the chassis itself into key components such as a cast magnesium strut tower caps. Not only will this allow greater flexibility in wide series production, it also likely made production of four lightweight “aluminum chassis” A5 mules considerably easier as it very well could also make construction of the quattro Concept considerably easier. It all adds up.



It’s about this point in our story that we realize I’ve knocked out 1400 words without talking much about the A5 2.5T prototype, what we learned about it or how it drove. For this reason we’ve separated that out into a second portion of the story. Stay tuned tomorrow for that.



Editor’s Note: Read the rest of the story in Part 2 HERE .




For more discussion on this story, click on the link to our discussion forums to the left.
For more photos of the car in this story, click on the link to our gallery at the right.



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