Basically what it is a "continuously variable transmission" which allows better gas milage, mainly for auto or autostick, instead of the use of a combination of gears, friction plates, hydraulic fluid and a torque converter it uses belts and pullies. These are only available in Europe and Japan, according to the artical, it also says they are for use on cars 2.0L or higher.
Direct Ignition Engine
By contrast, a direct-injection system allows exact control over not just the amount of fuel entering the combustion chamber, but when the fuel enters the combustion chamber. It even controls the shape of the fuel charge and the flow of air inside the combustion chamber! The benefits of all this precision can get pretty complex, but the short answer is that direct injection allows each tiny fuel molecule to be used with maximum efficiency, thus resulting in better horsepower and gas mileage. It also allows for a complete fuel charge burn, even when unburned exhaust gas is re-circulated back into the combustion chamber, which means reduced emissions and cleaner air. http://www.edmunds.com/news/innovations/articles/43848/article.html
That is the low down on the QG18DD. It sound like they wanted top performance while maintaning good mpg on gas. This is the euro/japan QG.
There was an article about direct injection in November SCC I believe. It sounds great, and there are a lot of tuning things they can due with it for emissions and performance. They said the reason that none are sold yet in the US is that the gas isn't good enought, though Mitsu may be trying to sell one shortly. I believe the problem was sulfer? If thats the case, maybe they will sell them in the Peoples Republic of California sooner, since we already have to pay more for low sulfer gas.