2009 BMW Advanced Diesel X5 xDrive35d

Engine Technology Spotlight

By Kevin Gordon

02.09.2009

BMW X5 35d Profile Picture

BMW’s proposal:  425 lb-ft of torque, a 0-60 mph in less than seven seconds, 26 mpg on the highway, 585 miles of driving range, seating for seven, all in a vehicle that weighs more than 5200 lbs. These are the highlight specifications from BMW’s recently released X5 xDrive 35d. Under its hood resides an oil burning 3.0 liter force-fed inline-six. The same motor is available in a 3-series, which makes the same horsepower and torque numbers, but improves the rest of the variables due to a better power-to-weight ratio. I recently had the chance to spend a night with a highly optioned version of the X5 and it left me wanting to learn more about this new inline-six.

The mill motivating this 2.6 ton Sports Activity Vehicle (SAV) burns something called diesel. You know – that stuff that comes out of the lonely pump at your local gas station. You’ve seen it before (unless your local station does not sell diesel) – it has an odd-colored handle and there is a black/brown puddle of goop in front of it. For most Americans, diesel is and has been a dirty word, the liquid of truckers and old Mercedes wagon drivers. This modern diesel motor is a completely different lady. Gone are the days of loudly-clattering idles and plumes of blue smoke. She has been sent to reform school and has manners that would fit in at any Concours d’Elegance.

Why would BMW be bringing a diesel motor to North America now? The first reason appears to be BMWs attempt to ride the coattails of the green movement. They are trying to change the image of diesel in the eyes of Americans and position it as a way to be greener. Because there is more energy in every drop of diesel, it returns higher miles per gallon (when compared to gasoline), and as a result it releases less greenhouse gasses from the tailpipe. This is at least what BMW is going to spend their advertising dollars attempting to convince buyers in the US. The second reason is BMW as a global company spends a significant amount of their research and development dollars on diesel technologies. Sixty-seven percent of BMWs sold in Europe are powered by diesel engines. The logic appears to be to leverage this investment and knowledge base in America, where this engine is sold as a premium option. Fundamentally, this is the same strategy as the hybrid car/SUV. Buy a slow, poor handling car/SUV that returns higher miles per gallon, at a premium price. The main difference is that these diesels are not slow, and they basically handle the same as their gasoline counterparts.

BMW 35d Engine

In the past, the spent gasses of a diesel motor pumped out pollutants far more dangerous than greenhouse gasses. These toxic gasses included nitrous oxide (NOX) and ammonia. These combustion byproducts have been greatly reduced by an advanced SCR catalyst and urea injection. BMW has renamed the bathroom humor target urea, to the dinner party-friendly AdBlue. This technology turns those harmful byproducts into Nitrogen (N2) and water vapor (H2O). AdBlue is stored in a 4.5 gallon reservoir, which provides enough capacity to only require a refill every 15,000 miles. This range is conveniently the same as the service interval for modern BMWs, and is covered under their standard maintenance plan for the first 4 years or 50,000 miles.

Between the front wheels of these vehicles is quite the technological tour de force. From the BMW advanced diesel press release:

Maximum power, supreme efficiency: The first BMW Advanced Diesel with BluePerformance is particularly well-suited to combine the driving dynamics and motoring refinement of a premium automobile with the most current and demanding standards for preserving resources and reducing emissions. Featuring exceptional power and torque, the 3.0 liter inline-six diesel is one of the most fuel-efficient and economical engines in its class.

Applying Variable Twin Turbo Technology, a small turbocharger first cuts in at low engine speeds. Thanks to its low inertia, this turbocharger develops boost (and extra power) in response to even the smallest movement to the gas pedal and without the slightest delay. As engine speed increases, the second, larger turbocharger cuts in, developing maximum torque of 425 lb-ft at just 1,750 rpm. Interaction of the two turbochargers is controlled by the particularly efficient, high-performance electronic engine control unit.

In addition to the above Variable Twin Turbo Technology, new technical highlights of BMW Advanced Diesel – presented for the first time in 2007 – include an aluminum crankcase and third-generation common-rail direct fuel injection. Featuring precision-quality precise piezo-injectors to deliver the precise dosage of fuel into the combustion chambers with the smallest volume of pre-injection, the third generation system ensures a particularly clean injection process with optimized fuel consumption, emissions figures and running smoothness.

Given all of these qualities, BMW’s 3.0-liter diesel with Variable Twin Turbo has won the prestigious International Engine of the Year Award multiple times – more than any other prize or acknowledgement. The engine is featured in a large number of models in Europe and is now expanding its global story of success as the BMW Advanced Diesel with BluePerformance.

It is a hard sell, putting diesel up against the green image of a Prius or the upcoming Honda Insight. Putting this engine up against a Lexus RX450h might be a bit of a better proposition. So does the equation work out in the favor of the 35d motor? If you answer yes to the majority of the following questions, then it might be right for you. Do you care about reducing your carbon footprint? Do you want to see 60mph flash by in less than seven seconds? Do you really hate getting out of your car to refuel? Is torque more important to you than horsepower? If I were in the market for the V8 version of the X5, I would have to take the diesel motor into serious consideration. It is a very impressive vehicle with thrust that must be felt to be understood.

Below the BMW commercials are included for your viewing pleasure:

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Author: Kevin Gordon

Kevin is Autosavant's owner and Editor-in-Chief, responsible for setting the overall strategy and editorial direction of Autosavant. He's also the primary contributor to Autosavant's YouTube channel (youtube.com/autosavant) where you can find a comprehensive library of new-car reviews.

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