Submitted via IRC for AndyTheAbsurd
It's called Spark Controlled Compression Ignition, and Mazda made it work.
Despite rumors to the contrary, the internal combustion engine is far from dead. Recently we've seen several technological advances that will significantly boost the efficiency of gasoline-powered engines. One of these, first reported back in August 2017, is Mazda's breakthrough with compression ignition. On Tuesday, Mazda invited us to its R&D facility in California to learn more about this clever new Skyactiv-X engine, but more importantly we actually got to drive it on the road.
The idea behind Skyactiv-X is to be able to run the engine with as lean a fuel-air mixture (known as λ) as possible. Because very lean combustion is cooler than a stoichiometric reaction (where λ=1 and there is exactly enough air to completely burn each molecule of fuel but no more), less energy is wasted as heat. What's more, the exhaust gases contain fewer nasty nitrogen oxides, and the unused air gets put to work. It absorbs the combustion heat and then expands and pushes down on the piston. The result is a cleaner, more efficient, and more powerful engine. And Skyactiv-X uses a very lean mix: a λ up to 2.5.
(Score: 2) by bradley13 on Wednesday January 31 2018, @09:01AM
"WE had lean-burn gas engine before, but it went away because of NOX emission problem"
NOX is the result of accidentally burning the nitrogen in the air, during combustion. This happens because of two things:
- Availability of oxygen, which would really rather combine with something more easily combustible. Hence, a lean fuel mixture is a necessary prerequisite.
- High temperature. Nitrogen doesn't particularly want to be oxidized - in fact, the reaction is endothermic. Diesels, for example, burn hotter than gasoline engines, which is why NOX is a problem for them.
According to TFS: They are running lean and low temperature. Hence, NOX should not be a problem.
Everyone is somebody else's weirdo.