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Mazda delays North American launch of Skyactiv diesel

9 January 2014

Mazda has delayed the North American launch of its Skyactiv diesel passenger car until further notice. The introduction of the 2.2 liter Skyactiv-D diesel has been postponed due to emission issues.

It is the second postponement of the Skyactiv-D market launch. The engine was originally planned for the 2014 Mazda6 model that was to be available from the Fall 2013. In September 2013, Mazda said it would delay the Skyactiv-D launch until April 2014 due to complications with emission testing and certification for the California market. The most recent postponement is indefinite, indicating that the Skyactiv diesel emission system may need to go be back to the drawing board.

Mazda has acknowledged that the engine has problems with meeting the emission standards. “While Mazda understands its Skyactiv-D can meet emission regulation requirements without the use of a NOx after-treatment system, it was decided that further development is required to deliver the right balance between fuel economy and Mazda-appropriate driving performance,” said the company. “Further information on the program, including a timeline of launch for North America, technical specifications and fuel economy will be available at a later date, closer to launch.”

The Skyactiv-D engine has been originally designed to meet Tier 2 Bin 5 emissions without the use of NOx aftertreatment. Bin 2 emissions could be achieved with a modest 75% deNOx aftertreatment system, according to a technical paper presented by Mazda at the 2013 SAE Congress.

US-market diesel models from all competing suppliers use aftertreatment technologies for NOx control—urea-SCR or NOx adsorber catalysts (NAC) in some smaller size engines. All light-duty diesels in the North American market also use diesel particulate filters (DPF) for PM emission control.

The Skyactiv-D diesel engine technology features a low compression ratio of 14:1 for NOx and PM emission control via optimized combustion timing. The low compression ratio also allowed for a weight reduction thanks to the use of an aluminum cylinder block, thinner cylinder head walls and lighter pistons. The engine utilizes multi-hole piezo injectors capable of up to nine injection events per cycle. Variable valve actuation (VVA) is used for rapid engine warm-up, to recirculate some of the hot exhaust gas into the intake port to increase the air temperature. The engine also uses a two-stage turbocharger.

The Skyactiv-D 2.2 liter diesel engine was first launched in Japan, in the 2012 Mazda CX-5 model. It was the world’s first passenger vehicle diesel engine to meet Japan’s 2009 emission standards (“Post New Long-Term Emissions Regulations”) without NOx aftertreatment. However, the JP 2009 NOx limit (0.08 g/km) is more relaxed that the US Tier 2 Bin 5 limit (0.07 g/mi = 0.044 g/km) and the respective testing requirements are different.

Source: Mazda