In the high-stakes, high-cost battle among global automakers to develop ever more efficient vehicles, one of the biggest breakthroughs in internal combustion engine technology in years looks to be coming from one of the industry’s smaller players.
Japan’s Mazda Motor Corp has zoomed past its larger global rivals to develop an engine which ignites gasoline using combustion ignition technology, a fuel-saving process considered something of a holy grail of efficient gasoline engines.
As global emissions regulations get tougher, not only could Mazda’s technology prolong the life of internal combustion engines, it could also improve “greener” engines as they can be used to produce more efficient gasoline hybrid and plug-in hybrid vehicles.
Mazda will showcase the Skyactiv-X technology at the Tokyo Motor Show this week. When it launches the engine in 2019, the automaker says it will deliver as much as 30 percent fuel efficiency over its Skyactiv-G engine, already one of the most fuel efficient gasoline engines on the market.
“Our resources are limited, so unlike bigger automakers, we don’t have the array of options in which to invest our R&D funds,” said Mitsuo Hitomi, managing executive officer at Mazda who oversees engine development. “That’s why we’re betting on this technology ... We were determined that no matter what, we would develop this engine,” Hitomi told Reuters in an interview at the company’s headquarters in Hiroshima.
Churning out around 1.6 million in annual vehicle sales, Mazda accounts for only a sliver of global car sales, and its R&D budget is roughly a tenth that of automaking giant Toyota Motor Corp. Many automakers with big spending budgets have invested heavily in developing a host of new powertrain technologies, including gasoline hybrids, battery electric cars and fuel cell vehicles, as fuel efficient alternatives to gasoline and diesel vehicles.
But Mazda believes fuel-sipping engines are a better way to reduce carbon emissions than cars powered by fossil fuel-generated electricity, focusing on the Skyactiv-G high-compression gasoline engine, and its diesel cousin, the Skyactiv-D. Its latest technology is a variant of homogeneous charge combustion ignition (HCCI) technology, which marries the clean-burning qualities of gasoline engines and the fuel economy and grunt of diesel engines to produce an efficient, powerful engine.
PRECISE TIMING REQUIRED
Mazda’s engineering team began developing the engine around the time it completed developing its Skyactiv-G engine, which came out in 2011.
From the start, solving the multiple variables required to balance performance with successful compression ignition was a challenge so complex and frustrating that there were “countless times” the team wanted to throw in the towel, Hitomi said.
Engineers at General Motors, Honda Motor Co and other automakers have also pondered how to develop a cost-effective way to control the HCCI process, which requires precise timing inside the engine chamber to achieve efficient ignition. Hitomi and his team came up with a relatively simple solution — to facilitate sparkless ignition, use a spark plug to light a high-pressure “fireball” inside the chamber to compress the super-lean mix of fuel and air.
The process is controlled by precisely monitoring each movement in the combustion chamber, enabling visibility of when the intake valve allows air to be drawn into the chamber to when the fireball is ignited. ”Kudos to them for taking the next step,” said Paul Najt, Group Manager of Research & Development at GM, which began showing an early HCCI prototype around 2007.
GM has since applied HCCI technologies to develop smaller, turbocharged engines, but Najt said the automaker was not developing a full system at the moment due to cost concerns. In the meantime, it has released gasoline hybrid and other electric models.
A MONSTER OF AN ENGINE
Hitomi said Mazda’s spark plug breakthrough came during a crisis point around two years ago, when the development team showed him an early rendition of the engine. “It had so many parts to it, like separate controls for variable valve timing and intake and exhaust levels, that it had become a monster of an engine,” too costly to produce, he said. The team then “performed massive surgery” to simplify the engine, using a spark plug to achieve an even compression ignition process and stripping unnecessary functions.
Now the Skyactiv-X engine consists of just three additional key components compared with the Skyactiv-G: in-cylinder sensors to monitor the combustion process, a high pressure fuel system to create the optimal fuel mix and a supercharger. The cost of the new engine ”falls somewhere between a gasoline and diesel engine”, Hitomi says.
Massachusetts Institute of Technology Prof. William Green, who has worked with HCCI development teams at U.S. automakers, said Skyactiv-X’s efficiency gains may be limited compared with hybrids and the even larger longer-term potential benefits of EVs. But the automaker could win over customers looking for an inexpensive, fuel-saving option which does not require battery recharging time or infrastructure, he added. “It has the advantage of being simple and straight forward, not expensive, and practical. Those are a lot of advantages.”
