2020 Mazda Skyactiv-X

It has been declared the most innovative technology development of 2019 and has won other prizes, but this is not a new DiesOtto. You could compare the engine to a Diesel in terms of consumption, although it doesn't quite reach that yet, and the compression ratio is similar at 16.3 : 1, but the term 'compression ignition' is an advertising slogan and is nothing special with what really happens in the combustion chamber.

A spark plug can only form sparks during a voltage flashover. This then ignites a mixture. This can be somewhat richer around the spark plug and leaner in the rest of the cylinder chamber. A previously compressed mixture is always ignited, so every ignition in a petrol engine is a compression ignition. One correctly pushed the geometric compression up to 16.3 : 1 and then turned to a possible comparison with Diesel technology.

But apart from the high compression ratio, the engine has nothing in common with a Diesel, not even the Diesel-like lean combustion that is attributed to it. If that was the case, it would have to have at least an SCR catalytic converter with AdBlue injection. But according to Mazda's press release, it doesn't. They say it regulates its lean mixture via exhaust gas recirculation. But that can't be very much, because that would be detrimental to fuel consumption.

As expected, the engine comes closer to the Diesel consumption than other petrol engines, but does not reach it. The most credible figure is 5.4 litres per 100 km (others 6.4 l/100km) on a very fuel-efficient lap. Diesel engines with two litres of displacement and a turbocharger can still do a little better. Much worse are even the values for torque. It should be described as an economical petrol engine with further sophisticated Atkinson-Miller architecture.