In August, Mazda unveiled plans for world’s first compression ignition (CI) gasoline engine. With this new technology (Skyactiv-X), the OEM claims to have designed a vehicle that will largely eliminate the need for spark plugs in petrol engines, increasing fuel efficiency by as much as 30%. Skyactiv-X should be Mazda’s next-generation engine that uses spark controlled compression ignition and will be available as from 2019.
The SkyActiv-X uses a form of compression ignition similar to a diesel engine and it can also seamlessly change over to a regular spark ignition like any gasoline engine when needed. The whole concept of homogeneous charge compression ignition has been at the center of debates for years. However, the difficulty of accurately controlling when combustion occurs greatly delayed the implementation process. Mazda stated that they found a way to use the spark plug itself to control the timing of compression ignition. The objective is to achieve a higher compression ratio and therefore increase the engine efficiency while reducing nitrogen oxides emissions.
Providing that there no single “lever” to control auto-ignition in a CI engine, several factors can affect when the combustion occurs. Ambient air temperature and pressure, fuel quality, air-fuel ratio, turbocharger boost, engine speed, engine load, and valve timing are some of the factors that can greatly affect the combustion. For instance, the heat in some cases may cause the fuel to detonate at the wrong time.
This news has come as a major breakthrough whereas other OEMs have been trying to develop this technology for decades. In parallel, engineers have also been working on exploiting auto-ignition towards higher compression and consequently more efficiency. General Motors, Honda, and Hyundai have even demonstrated variations in laboratory prototypes over the past few years.
This technology may further increase the existential threat affecting diesel engines because its fuel economy could match diesel’s performance without high emissions of nitrogen oxides or sooty particulates. However, this also questions the place of Internal Combustion Engines (ICE) in the long-term strategy of OEMs facing the overall context of decarbonization of road transport.
This announcement places ICE at the center of Mazda’s strategy, days after the company said it will work with Toyota to develop electric vehicles. By contrast, other OEMs have taken the decision to further develop the electrification of their vehicles stressing they do not see a future in traditional ICE. In that respect, Volvo recently announced all its new cars would be built with electric or hybrid engines from 2019.
By Logos Public Affairs