Mazda will delay the U.S. launch of its 2.2-liter "SkyActiv-D" four-cylinder diesel engine, but the company says it has a good reason.

The Japanese automaker said more development work was required to "deliver the right balance between fuel economy and Mazda-appropriate driving performance," and that this would push the engine's launch past the anticipated Spring 2014 date.

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Mazda noted that the SkyActiv-D is already clean enough to meet U.S. emissions standards without a urea-injection after-treatment system--setting it apart from virtually every diesel engine slated to be sold in the U.S.

The lack of after-treatment hardware should also make it relatively cheap to install the diesel in Mazda's existing models; it's architecturally similar to the SkyActiv-G gasoline engines used in the Mazda 3 compact and CX-5 crossover.

So the diesel is suitably green, which means the added development time may be needed for the other half of the equation: performance. The SkyActiv-D may have good fuel economy, but not enough "Zoom-Zoom."

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In diesel models available overseas, the engine producec between 148 and 173 horsepower, and between 280 and 310 pound-feet of torque.

While the SkyActiv-D engine hasn't made an appearance in U.S. showrooms, it has spent plenty of time on the track. Several 2014 Mazda 6 diesel racers were campaigned in Grand Am lats season, and Mazda will enter a diesel prototype in the inaugural season of the TUDOR United Sports Car Championship.

That should only whet the appetites of diesel fans. Mazda didn't set a new launch date for its diesel, but when it finally arrives the SkyActiv-D will most likely be available in the 6 sedan.


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