The upcoming new Mazda2 (known as Demio in Japan) will feature the SKYACTIV-D 1.5, a newly developed 1.5-liter clean diesel engine making use of the company’s next-generation SKYACTIV technology. Mazda unveiled the 1.5-liter diesel unit in the Mazda Hazumi concept at the Geneva Motor Show in March. (Earlier post.)
Similarly to the next generation SKYACTIV-D 2.2 clean diesel engine available in models such as the Mazda CX-5, the SKYACTIV-D 1.5 was developed in the pursuit of ideal combustion despite a very low compression ratio. (Earlier post.) The engine offers dynamic performance, including torque equal to a 2.5-liter gasoline engine and linear acceleration all the way up the rpm range. It also features excellent environmental performance without resorting to expensive NOx aftertreatment systems.
Along with utilizing numerous technologies from the SKYACTIV-D 2.2, additional advances were made to the SKYACTIV-D 1.5 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.
The all-new Mazda2 featuring the SKYACTIV-D 1.5 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.
The diesel will be combined with Mazda’s i-stop idling stop technology; i-ELOOP brake energy regeneration system; and high-efficiency SKYACTIV-DRIVE automatic transmission or SKYACTIV-MT manual transmission. Mazda suggests that the set of technologies will help the all-new Mazda achieve among the highest level test mode (JC08) fuel economy figures for a vehicle powered solely by combustion engine in registered vehicles excluding hybrid and micro-mini vehicles in Japan, as well as improved practical fuel economy.
The engine has a displacement of 1.497 liters; bore x stroke is 76.0mm x 82.5 mm. Maximum power output (net) is 77kW (104 hp) at 4,000 rpm; maximum torque (net) is 250 N·m (184 lb-ft) from 1,500-2,500 rpm.
Key new features of the SKYACTIV-D 1.5, many making their debut with this engine, include:
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). (SKYACTIV 2.2 diesels use a compression ratio of 14:1.) Reducing the compression ratio in a diesel decreases the compression temperature and pressure at TDC. Consequently, ignition takes longer even when fuel is injected near TDC, enabling a better mixture of air and fuel.
To realize ideal combustion timing and duration as well as clean emissions at the same time, Mazda uses this premixed compression ignition combustion by controlling ignition timing based on model-based prediction of ignition delay in the low compression ratio engine.
Cooling loss is suppressed 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 systems, resulting in improved fuel economy, environmental performance and performance feel.
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 delivers plentiful boost pressure from low through to high engine speeds.
Water-cooled intercooler integrated into the intake manifold improves acceleration response and turbocharger efficiency.
Environmental performance to meet Japan’s Post New Long-term regulations and Euro6 emission standards without an expensive NOx aftertreatment system.