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2009 Audi Q7 3.0 TDI quattro Road Test

Audi's diesel story started before 1989, but things really began to get interesting

Charge! On diesel, that is. The Q7 leads the oil-burning revolution. (Photo: Justin Couture, American Auto Press)

around this time, twenty years ago. This was when Audi, a brand best known for quattro all wheel drive, did something very innovative with the oil burner. Teaming up with Bosch they launched what would be the world's first common-rail turbodiesel-powered car, a giant step forward not only for Audi, but for the industry as a whole. Neither big, nor powerful, the Audi 100 TDI's 125-horsepower 2.5-liter inline-five turbodiesel opened a new chapter for diesel power.

Over the past two decades diesels have undergone tremendous innovation, and although North America has missed out on a lot of the action, we're starting to see some of these new clean diesels trickle into our market. Many powertrain ideas found in high-performance cars today, which are sometimes taken for granted, such as the variable geometry turbo or piezoinjectors, wouldn't be around if it weren't for the development of the diesel engine. And these technologies probably wouldn't be available - or at least not introduced as quickly as they were - if it weren't for that darn, grid-sweeping and series-dominating R10 TDI race car that's been cleaning up at Le Mans and ALMS for the past couple of years.

Big investment will make this badge a possibility on the back of North American bound Q7s as of early '09. (Photo: Justin Couture, American Auto Press)

Every year, Audi budgets about $3 bn towards powertrains, and quite a lot of that money, year after year, has been spend on a new generation of diesel engines. As of late, a considerable portion goes to making sure that its engines will pass emissions all around the world. In fact, Audi's confidence levels on the subject of emissions are so high that it's claiming the new 3.0 TDI is the world's cleanest diesel.

For Audi, the re-launch of diesel in North America will focus around the Q7. It's the best suited vehicle for multiple reasons, starting with the reality that the Q7 was the first Audi designed primarily for North American consumption. Also, efficient yet torque-rich diesel engines offer the most impact when fitted to large, heavy SUVs, plus competitors Mercedes-Benz and BMW are/will be present in our market with diesel SUVs, and the last but not least important reason Audi's SUV was chosen was because the Q7 has been a hotbed for Audi's diesel R&D.

What an engine! Quiet, silky-smooth, and gutsy beyond measure. A grade A+ powerplant. (Photo: Justin Couture, American Auto Press)

Audi is building a veritable diesel empire within the Q7 range. There are now two different engines available, including a smallish sounding 3.0-liter TDI V6 and the 4.2-liter V8 TDI, the latter of which at 326 horsepower and 560 lb-ft of torque is currently the most powerful diesel production SUV. To maintain its supremacy in diesel performance, Audi is launching the world's most powerful diesel automobile, the Q7 V12 TDI with its 6.0-liter twin-turbocharged V12 TDI that makes 500 horsepower and an astonishing 757 lb-ft of torque - equal to Mercedes' twin-turbocharged gasoline-powered V12 SL65 AMG. It'd have more, but the six-speed auto that it's equipped with would break under the stress. If its 5.5 second dash to 60 mph and 20 mpg average fuel economy isn't impressive, you really need to have your senses recalibrated.

The Q7s that we'll be getting have quite literally half of that V12 engine with identical bore and stroke measurements; it's a 90-degree V6 that's 3.0 liters in displacement, which incidentally is the same size as the Mercedes-Benz “320” series diesel engine in use in the GL/ML/R and Grand Cherokee CRD.

The only way you can tell it's a diesel is by its low 4,500 rpm redline. (Photo: Justin Couture, American Auto Press)

It's also the same size as BMW's engine, expected to arrive here this fall. Audi has been receiving critical acclaim for this engine since it was launched in the Q7 back in '06, so what's taken the brand so long to ship it to this side of the Atlantic?

One word: emissions. This four-letter word has been giving diesel engineers gray hairs, as trying to figure ways around the ultra-strict, diesel-snuffing Tier 2 Bin 5 emissions regulations that are employed is mind-numbing work. To give a comparison, the famously strict Californian measurement mandates that NOx emissions be 0.07 g/mi, which is much lower and much harder to meet than the Euro5 regs, at 0.29 g/mi, and at the time of the engine's release, 0.40 g/mi. The solution, as has been mentioned hundreds of times, is AdBlue, the water-based urea injection treatment first used by Mercedes-Benz in combination with an oxidation catalyst and a diesel particular filter, proven methods for trapping and then ridding a vehicle's exhaust system of unwanted emissions, turning everything into nitrogen gas and water.

Diesel goes in where the black cap is, AdBlue goes in where the silver cap is. You won't need to bother with that though; Audi's techs take care of it when it's brought in for servicing. (Photo: Justin Couture, American Auto Press)

A good deal of reengineering was required to make the Q7 meet North American emissions standards, as it isn't just a matter of sticking another box on the exhaust system as is the case with catalytic converters. Audi's engineers focused primarily on reducing the “raw” emissions, as in direct untreated exhaust, to reduce NOx wherever they could, and started directly at the fuel injectors. The upgraded engine receives new Bosch piezoelectric fuel injectors with eight micro-nozzles that are now set at 29,008 pounds per square inch of pressure, up from the 23,206 psi seven-nozzle units from the European model. This amount of pressure is powerful enough to cut clear through your hand, yet, at the same time, precise enough to deliver multiple injections of diesel per cycle, improving the efficiency of the combustion process and reducing emissions. It makes the engine smoother, too.

Also helping the engine itself run cleaner is a combustion chamber pressure monitor, a world first. Mounted within the glow plug, it keeps tabs on the amount and quality of fuel entering the chamber, and adjusts everything in order to keep combustion as optimal as possible. Changes to the engine to increase EGR (recycled exhaust gases into the engine during combustion) helped, as do improved turbo technologies. Of course, there are also the adjustments to the fuel tank area to make space for that AdBlue container.

Comfy, cozy... the Q7's cabin is first class treatment, especially if it's optioned out with high-end goodies. (Photo: Justin Couture, American Auto Press)

Additionally, Audi has made provisions for colder weather temperatures, such as the 14 F that was reached during our drive. Given that AdBlue begins to freeze at 12.2 F, the AdBlue tank, connectors and pipes are heated, and will warm the AdBlue solution so that it doesn't freeze and is ready to go at the twist of a key. Likewise, new glowplug technology means you need not wait more than one or two seconds to fire it up; the plugs heat up to 3,632 F almost instantly.

These changes have an effect on the engine in terms of its output. The European 3.0 V6 TDI engine, with the less powerful and less advanced injectors, makes 240 horsepower, whereas with the new equipment it makes 221 horsepower. It sounds like a bit of a step backwards, but it really isn't given that torque, the figure that talks with regards to diesels, remains unchanged at a mammoth 406 lb-ft. That's 8 lb-ft more than what the Benz diesel makes, and enough to secure a brisk 8.4 second jaunt to 60 mph, 0.2 seconds quicker than an ML 320 CDI. Note that out of the Mercedes-Benz models that have this engine, only the E-Class features AdBlue.

Six-speed automatic can handle the torque, but on the new V12 version, they actually had to limit thrust. (Photo: Justin Couture, American Auto Press)

Average fuel economy of the Q7 V6 TDI is rated at 25 mpg, in a mix of city and highway driving, which is better than the Q7's 3.6-liter V6 gas engine that averages 19 mpg, or for that matter the 16 mpg average of the 4.2-liter V8 gasoline engine. Although Audi didn't have any towing figures on hand, the non-AdBlue-equipped Q7 V6 TDI can tow 7,054 pounds.

And what of the engine itself? It's smooth, for sure, quieter than the 4.2-liter TDI and quieter than the Mercedes-Benz engine I sampled in a Grand Cherokee CRD. The upgrades really smoothen out the engine, from the usually strong and husky diesel vocals at idle, and during starting acceleration to a much lesser degree. Of course, there's also no stinking or smoking thanks to the emissions equipment and our much cleaner low-sulfur diesel fuel.

It's all too easy to forget that you're driving a diesel. In fact, diesels particularly suit larger vehicles like the Q7. Their low-down torque gets them up and moving quickly, and gives them the necessary shove to push all that mass forward right up to highway speeds and beyond, even when loaded down with people, gear and trailers.

To make sure that you don't forget that this Q7 is a diesel when filling up, it features a different nozzle neck to avert potential gasoline-related disasters. Also, next to the main cap, the Q7 also has an AdBlue filler, something that Audi is keeping in sight, but out of buyers' minds. AdBlue is dispensed at a rate of about 1.6 mL per mi, which in the grand scheme of things is a tiny amount. The system only needs to be filled at scheduled intervals, so keeping the Q7 running squeaky clean is a matter of bringing your car in when it's time for a scheduled service.

Being smooth, quiet and effortless to drive, the V6 TDI is a perfect match

Quattro is, of course, standard. (Photo: Justin Couture, American Auto Press)

for the Q7's luxury SUV personality. In fact, the Q7 will be the most posh diesel SUV on the market when it arrives next year. You'll be able to order it with the same wonderful Bang & Olufsen sound system featuring retractable tweeters and aluminum speaker cabinets, plus an Alcantara headliner and extended leather trim that covers the dash, console and door panels. It's the king of gadgets too, with second generation Adaptive Cruise Control that can cope with stop and go traffic, side assist blind-spot warning and of course Audi's MMI infotainment interface, which can be hooked up directly to your iPod. The Q7 has really become the A8 of the sport utility world, and in this segment Audi is unmatched by BMW, Mercedes-Benz or any other automaker. They're simply the finest.

So, what about the when and the how much? Audi isn't able to give any specifics yet, other than it'll arrive during the first quarter of '09

Audi: not just an AWD brand, but a diesel brand too. (Photo: Justin Couture, American Auto Press)

at the latest. Going by the price suggestions for Mercedes-Benz's diesel SUVs probably won't be much help, as they don't feature the costly technology that allows them to be 50-state legal. Instead, if I had to make an educated guess I'd say they'd start at around $60,000, which is a bit more than the gasoline-powered 4.2-liter V8 ($58,600). This figure might seem a bit tough to swallow, but reasonable considering the savings in fuel, the torque and therefore the towing capabilities, plus the refinement.

The diesels are coming, and while they can't arrive soon enough for some of us, Audi has certainly done an amazing job in dressing to impress.

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