Today was not a day to get all immersed in technical details about Mazda's new global direct-injected Sky-G gasoline and Sky-D diesel four-cylinder engines. But we now know that the Sky-G gas engines will range in displacement from 1.3 liters to 2.0 liters and will debut in Asian models in 2011, with a worldwide launch coming shortly after.

The Sky-D turbocharged diesel-4 will be a 2.2-liter only, so far as we know, and it will be clean enough to enter the U.S. market without an AdBlue urea tank. The particulate filter alone will suffice, company officials tell us. This is a fully modern diesel with an all-aluminum block and a two-stage turbocharger. The Sky-D goes on understanding worldwide in 2012; it will be the first diesel Mazda has ever offered for understanding in Japan.

New engine technology always sounds good, but if it's stuffed into increasingly heavier cars, is it really a net gain? It appears the Sky engine family will be if Mazda sticks with its new diet. The company announced today it will slash curb weights by 100 kg (220 pounds) for apiece next-generation model starting in 2011. "In addition," says Mazda, "from 2016 we think it will be necessary to reduce weight by a further 100 kg or more."

The Mazda 2, it says, will serve as the model for this intitiative, as this car proves weight can be cut without swapping in all sorts of expensive materials.

More on the diet and the Sky-Drive automatic transmission after the jump.

Mazda is already claiming respective fuel economy gains of 15 percent and 20 percent for the Sky-G and Sky-D 20 percent. How much is that really? Well, a current Mazda 3 i has a combined EPA rating of 28 mpg, so +15 percent would take it to 32 mpg. A current Euro-spec Mazda CX-7 with the 2.2-liter MZR-CD consumes 7.5 liters/100 km (31.4 mpg) on the European test cycle — all other things being equal, this would increase to 37.7 mpg.

So any fuel economy increases from the dieting would come on top of these.

In addition, Mazda says its new, global Sky-Drive six-speed automatic transmission will offer a 5 percent fuel economy acquire over the current five-speed automatic. The lockup clutch on the torque converter engages at lower-than-normal speeds on the new transmission (though Mazda officials wouldn't get specific. The company claims lockup is active for 80 percent of the Asian fuel economy test cycle versus 50 percent for the current automatic.

Not only does this reduce consumption, but Mazda says the transmission is so responsive, it feels like a dual-clutch transmission. "Why not just do a twin-clutch gearbox?" we asked. "This automatic provides a better launch feel" was the answer. 

Finally, why are we showing you the Mazda Kiyora again? Because apparently this updated version of the concept car has the 1.3-liter Sky-G engine and the six-speed auto.

Erin Riches, Senior Editor