In North America, much of the car buying population has historically avoided diesel-powered transportation like the plague. This is because, much like your in-laws, they have been regarded as loud, smelly and uncouth. And with good reason.
|1. While power is rated at 265 hp at 4200 rpm, this diesel engine provides significantly more torque than its gasoline counterparts; 425 ft-lbs at 1750 rpm to be exact.
2. Piston wrist pins have been offset in order to prevent pistons from rattling against the combustion chamber wall during the power stroke, thus reducing the ‘pinking’ sound commonly associated with diesels.
The twin-turbo 335i is on my short list of favorites from the past year. A sports sedan that is actually sporty is a rare bird indeed. Back in 2006 when the redesigned 2007 3 Series was unveiled, many people were surprised to see a turbocharged powerplant under the hood, instead of the traditional naturally aspirated straight-six. Imagine their shock upon learning that the very same engine bay is now home to a variable twin-turbocharged diesel engine!
There are, however, more reasons for North Americans to eschew diesels, aside from the loud and smelly factors. Most importantly, diesel fuel is more expensive at the pump.
According to Tom Bologa, Vice-President of Engineering for BMW North America, the common perception of the numbers at the pump aren’t all that accurate. While there is a tendency to compare diesel to regular octane fuel, the comparison should be made with higher-octane premium fuel. “For both performance and emission purposes, we compare diesel to premium gasoline,” says Bologa.
His point becomes all the more convincing when you consider that no BMW owner should ever be looking at the price of anything but premium fuel, because that’s all a BMW takes.
Bologa also points out that, “The premium price of diesel vehicles and fuel are offset by improved fuel consumption and higher trade-in value.” Diesel engines typically experience increased longevity because they rev lower and diesel fuel is more of a lubricant than gas, so engines last longer by design. Bologa believes that these short and long term gains are important when considering the benefits these specifically designed diesels have to offer.
BMW had many lofty goals for its 335 diesel project, including reducing CO2 emissions and improving fuel economy, while preserving driving performance and enjoyment in the process. In order to build a diesel that didn’t feel like a diesel, Piezo electric fuel injectors, which can inject up to five times per stroke, replaced the traditional mechanical units that are less efficient and can lose calibration. Additionally, the twin turbo setup was redesigned for this particular motor. The system is comprised of a small turbo, a large turbo, a wastegate and butterfly valves that allow either the small, large or both turbos to operate simultaneously - virtually eliminating turbo lag.
Behind the wheel the car doesn’t feel at all like a diesel – except for the massive amounts of torque. Sure the 335d doesn’t make 300hp like the 335i (just 265 ponies) but because of the lack of turbo lag and the low rpm production of power, the 335d blasts from a light with 425 ft-lbs of torque at just 1750 rpm.
Along with the experience of “the ultimate driving machine,” BMW employed a host of specific strategies to ensure the 335d would be attractive to North American consumers. For starters, the piston wrist pins have been offset in order to prevent pistons from rattling against the combustion chamber wall, thus reducing the ‘pinking’ sound commonly associated with diesels.
Another addition was a cast reinforcement beneath the crankcase in order to add structural rigidity and prevent noise.
Along with a lengthy list of technological advancements, one of the most important was made to reduce emissions. BMW devised a system whereby diesel exhaust fluid (DEF) is sprayed into the exhaust just before the catalyst. This then creates a mixture that enters the catalyst where a chemical process changes harmful Nitrogen Oxide (NOx) into Nitrogen and water vapor. The result is a significant reduction in greenhouse gases.
The combined result of these technological advancements is a quieter, cleaner running automobile.
So how does the 335d behave out on the open road? Over a two day trip across the countryside through various inclement weather and road conditions, the 335d demonstrated itself to be smooth, sophisticated and stable. My guess is that without the diesel badging, few people would ever notice the difference under the hood. Unfortunately there is no option for a manual transmission with the diesel motor because the components wouldn’t be up to the task in the long term. As it is, the 335d’s transmission has been sourced from the eight-cylinder BMW parts bin to ensure it can cope with all the diesel-powered torque.
This year, two diesel vehicles are finalists for the 2009 North American Car and Truck of the Year Awards. The fact that the Volkswagen Jetta TDI diesel and the Mercedes-Benz ML320 BlueTec clean diesel luxury SUV are finalists may mean that a public sway in perception towards diesels is not far off. Gone are the days when smelly old diesels would pink down the road, puffing black smoke while they searched in vain for a gas station with diesel.
With the 335d, BMW has proved that diesels can not only be good alternatives, but great alternatives. Let me sum this up for you: The 335d is a 3 Series BMW with 425 ft-lbs of torque, improved fuel mileage and higher residual value. This bold move by BMW to introduce a premium diesel lineup to the North American market is starting to seem less like a gamble and more like a sure thing.
Whisper quiet diesel engine
Initial purchase premium