Getting to know the new U.S. diesel-powered BMWs

3-Series | June 10th, 2009 by 6
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One of the most exciting news in the BMW world in the past year, was the introduction of two new diesel-powered BMWs in the United …

One of the most exciting news in the BMW world in the past year, was the introduction of two new diesel-powered BMWs in the United States: BMW 335d and BMW X5 xDrive35d. Launched during a period of time when the diesel and gasoline prices were moving downward, many believed that the timing could not have been worse. But six months later and with the oil price returning to its last year levels, these two new diesel bimmers are looking more and more appealing to everyone.

The 335d boasts a best in class EPA fuel economy of 23/36 MPG (city/hwy). This makes it the most fuel efficient BMW ever sold in the US, and also gives it the highest ever EPA MPG rating of any 6 cylinder vehicle ever offered in the US (gas or diesel). BMW X5 xDrive35d achieves an EPA rating of 19/26 MPG (city/hwy) and accelerates from 0-60 in 6.9 seconds, making it the fastest, most efficient Diesel SUV available in the US.

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To “sweeten” the deal even more, BMW announced that the 335d and X5d will quality for a tax credit. The 3 Series Diesel tax credit is up to $900 while the X5d up to $1,800.

We reviewed the 335d back at the L.A. Auto Show and it left a positive impression on us. In the upcoming weeks, we will have the new X5d for a few days and we’ll be able to test both during short rides, but most important, over a long drive across the country(more details on that next week).

But in the mean time, our close friend Kamil at CarGuyDad shares with us his experience with the new diesels and plenty of technical details.

Here is a preview of that:

Like on most new cars today, open the hood and you’ll see nothing. The engine is a three-liter, aluminum (yes, aluminum), DOHC, 24-valve, common-rail direct-injected, in-line six with a 16.5:1 compression ratio. The engine features variable intake manifold and double-VANOS valve control. All of that is supplemented by a pair sequential, differently sized turbos. Big air-to-air intercooler is located within the front bumper cover of both cars. The engine produces 265hp at 4200rpm, but more importantly 425lb-ft at a low 1750rpm. Unlike a traditional diesel there are no glow plugs, as the direct injection system has the ability to start a dead cold engine all by itself.

What the engine does have, as does just about every other new diesel, is urea injection. Here is how urea injection works: most of the diesel soot gets trapped in the particulate filter located just behind the exhaust manifold, where it eventually burns up. The stuff that gets through and/or the burned remnants (NO/NO2), get trapped in a secondary catalytic converter known as the SCR catalyst (selective catalytic reaction). When the urea is injected into the SCR, a chemical reaction occurs which generates ammonia (NH3). The ammonia in turn reacts with NO/NO2, converting it into nitrogen (N2) and water vapor (H2O). Got it? Chemistry lesson is over, class dismissed.

Did we get your attention? Then feel free to read further at CarGuyDad.