Insight: Why Mazda has pursued 'dream' petrol engine technology

Kiyoshi Fujiwara, Mazda’s R&D boss, told Autocar: “Step by step, we’ve developed the technology towards this goal. We’ve never looked at a different direction. Larger manufacturers have lots of people and they can do multiple things. But we decide on one thing - and we decided to work on this.”


The next step to that goal was Mazda’s Skyactiv-G petrol and Skyactive-D diesel engines. After that, Mazda focused
 on improving the heat ratio - the thermal efficiency of the Otto cycle - and combustion period and timing. This offered potential improvements to fuel economy and emissions without compromising performance - and it led Mazda to pursue compression ignition technology. 

Homogenous charge compression ignition (HCCI) - literally squeezing the air-fuel mixture until it combusts - is standard on diesel engines but had long been impractical for petrol engines because of the different fuel characteristics. The challenge of petrol HCCI is that it works within only a limited engine rev range, which changes depending on atmospheric conditions. The ideal solution is a petrol engine that combines compression ignition with a spark ignition, enabling it to be used in a far wider range. 

A compression-ignition petrol engine is “a dream” 
for engineers, according 
to Kudo, and to achieve it Mazda extended its usual development cycle. “We used to spend two years developing each technology,” he said. “But for Skyactiv-X, we have taken five. That level of time was needed to achieve the higher target.” 

Skyactiv-X engines will enter production in 2019, twinned with Mazda’s new Skyactiv platform. Within five years of that date, Mazda will refresh its entire model range with the new engines and platform. 

Mazda has yet to set specific targets, but it is aiming for 
the new engine to combine 
the emissions and economy of a Mazda 2 with a 1.5-litre Skyactiv-D engine with the performance of an Mazda MX-5 with a 2.0-litre Skyactiv-G petrol unit. 

Although Mazda is continuing to pursue combustion engine advances, it isn’t shying away from electric. It will introduce a mild hybrid and a battery EV in 2019 - and, by 2035, every Mazda sold
 will have some element of electrification. Progress in that area will be aided by a recent technical tie-up with Toyota. 

Again, there is a difference: Mazda’s focus is on ‘well-to-wheel’ emissions, which accounts for how the energy that goes into a vehicle is created. In that context, an EV is only clean if the energy powering it comes from a clean source. 

“We’re not denying electrification,” said Fujiwara. “By making CO2 savings on the combustion engine, we can reduce the burden on
 the hybrid.” The exact level
 of electrification in Mazda’s line-up will vary from country to country, taking into account power sources and legislation.