Not content with the efficiency gains of its high-compression, direct-injected, lean-burn SkyActiv engine range, Mazda aims to increase the thermal efficiency of its petrol engines by at least 50 percent by the end of the decade.
For those who never graduated with a degree in engineering, thermal efficiency measures the total amount of energy an engine is able to extract from its fuel, with conventional mass-market petrol engines being typically around 30 percent efficient.
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That’s well above the industry average, but Mazda Europe’s head of research and development, Kenichiro Saruwatari, reckons there’s plenty of room to improve.
Speaking to UK mag Autocar, Saruwatari said that efficiency levels of 60 percent are feasible using current technology, and without resorting to turbocharging.
Instead, Mazda will raise compression ratios from the SkyActiv G’s already-high 14.0:1 ratio to 18.0:1 – higher than some diesels.
With such a high compression ratio, ignition won’t require a sparkplug and the resulting combustion will burn the fuel/air mixture more thoroughly.
The challenge for now is to design the next generation SkyActiv G engines to stave off engine-destroying “knock” – a hazard at such high compression ratios.
But the payoff should be a range of engines that comfortably comply with future European and American emissions legislation, without needing the assistance of costly and heavy turbochargers or hybrid systems.
Can Mazda do it? We’ll find out in five years.