What's all the Clatter About HCCI?

HCCI Technology - GM and its Homogeneous Charge Compression Ignition fuel-saving engine tech - Auto News - Motor Trend

I've brought up homogeneous charge compression ignition (HCCI) before as an engine technology that could bring big fuel economy benefits. Basically HCCI operates like a diesel ignition, igniting a mixture of fuel and air by compressing it in the cylinder. It's quite a handful controlling this kind of combustion and currently HCCI engines cannot operate as such the entire RPM range. The breakthrough that GM has had is that its experimental engines can operate in HCCI mode at idle--that's a pretty big step. When you add up all the various fuel saving ingredients that comprise GM's stew, you'd get around a 10-15 percent bump in fuel economy.

Drivers who have had some seat time report that the transition between HCCI and spark ignition is audible but otherwise seamless. Certainly if spark ignition mode could be removed completely, then we'd have a real game changer on our hands. GM isn't the only company looking into HCCI and I'm quite certain we'll be hearing more about this technology as engine controls continue to evolve.

You can click on the above article for more info and click here for a GM press release.