[onewhippedpuppy]

Originally Posted by Tervuren

The article did not mention variable mechanical compression.

However it using an explosion of richer fuel/air near the spark plug to further compress the leaner fuel/air that was taken in during the intake stroke.

I think Infiniti has come out with a variable compression engine, also a cool idea.

Originally Posted by berettafan

so I read the first few paragraphs and I'm not clear on what's new here?

mazda wanted to use compression only to ignite an ultra lean fuel/air mixture but it wouldn't work so they brilliantly introduced spark to the mixture and boom, skyactiv x!

It's both a compression and spark ignition engine, and goes between the two modes depending on load. Best of both worlds between a diesel and gas engine, but using gas and at a cost comparable to a standard gas engine.