Mazda has pledged that its next generation of petrol-engined vehicles will be cleaner than electric cars because they will use efficiency-boosting compression ignition technology. The Japanese company is developing a new range of engines, called Skyactiv-X, which is set to replace the current Skyactiv-G range in 2019. They use compression ignition technology that has previously been used in diesel engines only. Mazda claims the results improve efficiency by up to 30% compared with its current petrol units, matching or even improving on its Skyactiv-D diesel range.
Mazda says this will enable Skyactiv-X engines to produce lower CO2 emissions than electric drivetrains from a ‘well to wheel’ perspective, which accounts for the whole life cycle of a vehicle including the fuel needed to power it. Compression ignition technology has not yet been used on a mass-production scale in petrol engines. The system, called Spark Controlled Compression Ignition, mixes petrol and air together in the engine’s cylinder like a conventional spark ignition engine but then ignites it using compression at lower load or with a spark at higher loads. This means that around half the volume of petrol is required for the same combustion level across most of the rev range. Mazda R&D boss Kiyoshi Fujiwara, who has overseen the programme, said this “very lean air-fuel mixture that is too lean to combust by spark ignition [alone] can combust by this method cleanly and rapidly”.
This enables “better thermal efficiency, improved fuel economy and lower nitrogen oxide emissions”, Fujiwara said. Other benefits include higher across a wider range of revs, thus improving engine responses and performance. Mazda has pursued this line of development because it believes spark ignition technology is reaching its peak. It also argues that although electric technology produces no tailpipe emissions, it is yet to represent a truly sustainable option on a global scale because much of the world’s electricity grids are still powered by fossil fuels.
As part of its Sustainable Zoom-Zoom 2030 programme, Mazda has pledged to reduce its corporate average well-to-wheel CO2 emissions to 50% of 2010 levels by 2030, before reducing them by 90% by 2050. Mazda will begin introducing electric technology to its range from 2019 but has stated that it will focus sales of these models in regions where sustainable energy is produced. It will continue to invest heavily in petrol technology beyond this point, citing a continued growth of combustion engine demand in other regions, such as developing economies.