Mazda plans a ‘petrol-diesel’ engine
Combining best of both worlds, Skyactiv-X is both frugal and clean
WHILE the buzz in the automotive industry is all about the coming age of electric cars, not every company has given up on the traditional internal combustion engine just yet.
Mazda, which is no stranger to different engine concepts and almost single-handedly championed rotary-engined cars in the modern era, has just announced that in 2019 it will launch the world’s first commercial petrol engine to use compression ignition, which combines the benefits of petrol and diesel engines. Dubbed Skyactiv-X, the engine will use a combustion method called Spark Controlled Compression Ignition (SCCI) to achieve petrol engine-like emissions with diesel engine-like fuel economy.
To ignite the air-fuel mixture the Skyactiv-X engine will alternate between using a spark (as in a petrol engine) and high compression (as in a diesel engine). This method produces diesel-like torque and fuel consumption but with far lower levels of nitrogen oxides (NOx) – the nasty air pollutants emitted by diesels that contribute to acid rain, global warming and respiratory conditions Due in 2019, Mazda’s petrol engine is able to combust with or without a spark.
such as bronchitis.
Mazda’s Skyactiv-X claims to solve the problem by delivering the best of all worlds: combining great torque and economy without causing coughing or melting the polar ice caps.
SCCI technology has been around for some time but has not been mass produced due to some technical challenges, which Mazda claims to have overcome by enabling a seamless transition between compression ignition and spark ignition.
It says compression ignition combined with a supercharger will increase torque 10-30 percent
and reduce fuel consumption by 20-30 percent over Mazda’s current Skyactiv-G petrol engine, and even equals or exceeds the latest Skyactiv-D diesel engine in fuel efficiency.
The Skyactiv-X engine forms part of Mazda’s ‘Sustainable Zoom-Zoom 2030’, a new long-term vision for technology development that looks ahead to the year 2030.
DIESEL CONTROVERSY Mazda’s ‘two-engines-in-one’ Skyactiv-X concept comes at a time when the petrol vs diesel debate is raging strongly.
Diesel engines, once championed for being more fuel efficient
and producing lower levels of the greenhouse gas carbon dioxide (CO2) than petrol engines, have recently received much negative publicity for producing other toxic air pollutants that are more harmful to humans, including
NOx and particulates. Diesels emit more NOx than petrol engines, and NOx was at the centre of the infamous ‘Dieselgate’ scandal uncovered in 2015 where the VW group and other automakers were caught cheating the pollution police by under-quoting the real NOx emissions of a number of their turbodiesel vehicles.
Because reducing NOx emissions increases an engine’s fuel consumption (and vice-versa), in real-world driving these cars achieved good fuel economy but at the cost of emitting much higher NOx levels than environmental regulations allowed.
But ‘defeat devices’ detected when these vehicles were in a lab, when being tested by authorities, and under these conditions reduced the engine’s NOx emissions to pass the pollution tests.
Diesel engines also produce more particulate matter (soot) that can penetrate lungs and can contribute to cardiovascular illness, cancer and death. Particulate filters in exhausts drastically reduce soot emissions but they require good operating conditions and regular maintenance. There are also still many older cars and trucks on the road that conform to earlier emissions standards.
As a result some governments are planning to discourage the use of diesel vehicles or even ban them from urban areas altogether. The mayors of Paris, Mexico City, Madrid and Athens have all said they plan to ban all diesel-powered cars and trucks from their cities by the middle of the next decade.
In the light of such drastic measures Mazda’s Skyactiv-X, by combining the cleaner emissions of petrol engines with the efficiency of diesels, could well help prolong the life of the internal combustion engine.