The new SKYACTIV-D 1.5l diesel engine

Mazda Motor Corporation has announced that the upcoming all-new Mazda2 (known as Demio in Japan) will feature the SKYACTIV-D 1.5l, a newly developed 1.5-liter clean diesel engine making use of the company’s next-generation SKYACTIV technology.

Similarly to the next generation SKYACTIV-D 2.2l clean diesel engine available in models such as the Mazda CX-5, the SKYACTIV-D 1.5l was developed in the pursuit of ideal combustion despite a very low compression ratio.

Inheriting technologies from the SKYACTIV-D 2.2l, additional advances were made to the SKYACTIV-D 1.5l to further enhance the engine and make it suitable for subcompact vehicles. Additional technologies include an expanded homogenous lean burn range, further reduction in mechanical resistance, and insulation technology to curb the increase in cooling loss associated with a smaller engine size.SKYACTIV-D 1.5l diesel engine

The all-new Mazda2 featuring the SKYACTIV-D 1.5l clean diesel engine will be introduced to the Japanese market where it will meet Japan’s Post New Long-term Emissions Regulations as a diesel-powered compact car. Combined with Mazda’s i-stop idling stop technology, i-ELOOP brake energy regeneration system, and SKYACTIV-DRIVE automatic transmission or SKYACTIV-MT manual transmission, the SKYACTIV-D 1.5l will ensure the Mazda2 achieve among the highest level fuel economy figures on JC08 test mode cycle, as well as improved practical fuel economy.

Key features of the SKYACTIV-D 1.5l

  • Development pursued ideal combustion efficiency despite the lowest compression ratio of any small displacement diesel engine – 14.8:1 – Among 2-liter engines or smaller, as of June 1, 2014.Skyactiv-D reduced compression ratio
  • Cooling loss is decreased by combustion mode transition control technology, and high dispersion solenoid injectors which, along with stepped egg-shaped pistons, help to reduce contact between the flame and chamber wall.
  • The range of homogeneous lean burn is extended through the adoption of high-pressure EGR and low pressure EGR system.
  • Engine cooling system features cooling water control valves (CCV) and water jacket spacers for improved combustion efficiency and reduced mechanical resistance.
  • Variable turbine geometry turbocharger with rotation sensor.
  • Water-cooled intercooler integrated into the intake manifold improves acceleration response and turbocharger efficiency.

Key specifications of SKYACTIV-D 1.5l

In-line four-cylinder direct injection 1.5-liter diesel engine:

Engine displacement: 1.497 Liters
Bore x Stroke: 76.0 mm x 82.5 mm
Compression ratio: 14.8:1
Max. output (net): 77 kW /4000 rpm
Max. torque (net): 250 Nm /1500-2500 rpm
Source: Mazda

Romain’s opinion:

The engine design adopted by Mazda is quite exotic with respect to global trend to increase compression ratio. Additionally, they claim to run partly in homogeneous lean burn combustion (So called HCCI for Homogeneous Charge Compression Ignition) which is quite tricky from a timing control point of view. Do you think the engine really operates in HCCI, even more if the compression ratio is quite low?

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