Alistair Weaver, VP of Editorial and Editor-in-Chief
This is exactly what the world needs. Just as capitalism sinks to its knees in a fog of bad debt, Audi has launched an SUV with a V12 diesel complete with 493 horsepower and 738 pound-feet of torque. The 2009 Audi Q7 V12 TDI is Audi's latest statement of extreme performance from Quattro GmbH, the same people who gave us the 420-hp R8 and 571-hp RS 6. Only it's a high-performance diesel-powered SUV.
This Audi Q7's most obvious rivals include the Porsche Cayenne Turbo and the Mercedes ML63 AMG, but the Audi is the only one of these to stop at the diesel pump. Soon we'll see this V12 diesel in the A8 sedan and possibly the R8, but for now, the 2009 Audi Q7 V12 TDI is the company flagship, the most powerful and expensive piece from Audi that you can buy.
This V12 diesel debuted in the Audi R8 TDI concept car that was shown for the first time at the 2008 Detroit Auto Show. Manufactured in Gyor, Hungary, the 60-degree V12 displaces 5,984cc, yet it's surprisingly compact despite its colossal displacement, only some 6.5 inches longer than the Audi's 90-degree V8 TDI and no wider. The combination of a 60-degree angle between cylinder banks (the optimal balance point for a V12), a stout block cast from vermicular graphite (40 percent more rigid than iron, yet 15 percent lighter), a chrome-moly crankshaft located by an iron ladder-type girdle, aluminum cylinder heads, and a relatively low compression ratio (for a diesel) of 16.0:1 all help to control vibration but without too much road-hugging weight.
The key to the engine's performance lies with the combination of turbocharging and high-pressure common-rail injection system. Each turbo feeds one cylinder bank, and the use of an adjustable vane design helps the turbos spool up quickly to peak boost of 25 psi. There's an intercooler for each cylinder bank as well. The high-pressure injection charges the piezo injectors with fuel at 29,400 psi. Each injector has an eight-hole nozzle, providing a fine, consistent spray of fuel. In theory, this produces more efficient combustion, increasing the power output while cutting fuel consumption and air emissions.
There are two particulate filters. And at partial throttle, up to 50 percent of the exhaust gasses are fed back into the combustion chamber to help reduce nitrous-oxide emissions.
The raw performance statistics are staggering. This V12 combines 493 hp at 3,750 rpm, with 738 lb-ft of torque from 1,750-3,250 rpm. The Cayenne Turbo can compete on pure power with 493 hp, but its 516 lb-ft of torque doesn't come close. The same goes for the 6.2-liter V8 in the Mercedes-Benz ML63 AMG, which delivers 503 hp and 465 lb-ft of torque.
The Diesel Experience This engine is not just an engineer's show pony; it's a very serious tool. Prod the starter button and the V12 settles into a deep, subdued growl. You can tell it's a diesel only because the tone is lower than it would be for a gas-powered V12. At low speeds the engine feels docile enough, but you never have any doubt about its potency. Give the throttle a deliberate boot and the Q7 responds with more vigor than any 5,743-pound SUV has a right to.
Audi claims the Q7 V12 TDI will accelerate to 100 km/h (62 mph) in 5.5 seconds, but it feels even faster when you're in the meat of the power band, such is the relentless surge of torque. It's almost comical in its intensity; you could worry a lot of genuine supercars in this Q7. What's more, the V12 sounds terrific. It's a very deep, very cultured roar, something you might replicate if you have your subwoofer turned up too far. Stephan Reil, the head of Quattro GmbH, admits that his team worked hard to increase the engine's volume. He's worried that they've gone too far, but we're not so sure. If you'd paid $180,000 for a ludicrously rapid SUV (pretty close to the cost of a Q7 V12 TDI in Britain, once you add all the taxes), you'd want to hear it.
Reil admits that the engine is capable of producing even more torque, but that 738 lb-ft (1,000 Nm) was a sensible limit for the gearbox. The six-speed automatic does a decent job of managing all that thrust.
Ripping up the Pavement The V12 retains the air suspension of the standard Q7, but it's been retuned. Via the MMI control system, you can choose between Comfort, Automatic and Dynamic settings. Automatic is generally the best choice, while dynamic is too aggressive for sensible road use. No vehicle this big or this heavy could ever mimic a sports car, but the Q7 can be hustled along with considerable gusto.
Body roll is exceptionally well controlled for an SUV, and while the steering could use a tad more feel, it's pleasingly linear in response. The standard carbon-ceramic brakes — with eight-piston calipers at the front — have no trouble killing the speed, even with 5,743 pounds to deal with. It's difficult to think of another vehicle on the market that's as "overspecified" as this Q7, as everything is built for speed in a very serious way.
Audi claims that the V12 has significant off-road ability but given that it rides on either 20- or 21-inch rims with stiff, low sidewalls, you're unlikely to be taking this particular Q7 on the Yukon Trail.
The Diesel Look Audi's stylists have been busy fitting vertical chrome bars to the front grille, bigger air intakes to feed the engine and intercoolers, and LED-type daytime driving lights. There are extended rocker-sill skirts to complement the new wheel arches, which are 1.02 inches wider at the front and 1.18 inches wider at the rear to enclose the massive wheels and tires. At the rear, the taillights sit in a darker surround and there is a pair of vast, oval exhausts.
These changes, coupled with the huge 20-inch wheels, visually lower this utility vehicle and give it a much more purposeful, carlike stance. The final statement isn't subtle, but the changes have been beautifully integrated.
The interior is a mix of leather, suede, aluminum and carbon fiber, all employed to fine effect. The Q7 V12 TDI is beautifully finished in the best Audi tradition, but whether it really feels special enough to justify its colossal price tag is open to debate here in Europe, where we're not accustomed to utility vehicles that make such a strong statement of privilege and power.
The Purpose of Diesel The 2009 Audi Q7 V12 TDI doesn't really need to exist. Viewed objectively, it offers few major advantages over an Audi 4.2 Q7 V8 TDI, which costs half as much.
Nevertheless, the Q7 V12 TDI will still find an audience. Though it's a diesel, it'll make its way into the hands of the super-rich, who'll probably already have a garage full of alternatives. These customers will enjoy a thoroughly engineered curiosity that makes little sense, but is appealing all the same.
The Audi Q7 V12 TDI shows you that the image of diesel is changing. It's no longer an expression of cheap practicality. Instead, diesel can be all about power, and that's a message we'll be hearing more often these days.
Edmunds attended a manufacturer-sponsored event, to which selected members of the press were invited, to facilitate this report.
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