Volume III, Issue 6, Page 25
Though a Saturn Aura was referenced in the story, lots of prototyping was done with an Opel Vectra as well, as equipped with the Ecotec world engine. 

ad the artful greed of Saudi Arabia and other oil producing nations stayed somewhat subdued, you wouldn’t be reading about this engine for several more years, if at all. It’s still in stages of experiment and has the same rough edges as any engine that deviates from the norm. Let’s see, we have the gasoline/electricity hybrid combination. We’ll have the soon-to-be-released hydrogen-powered engine. All-electric modules will be kept for very local and inner-city work. Aside from working on smaller motors that will be just as powerful as the ones GM replaces, there’s the HHCI, or Homogenous Charge Compression Engine.

Do we need this one, too? Maybe. Maybe not. Bicycles are extremely economical but not much fun up hills. Nor is jostling with a bunch of strangers in a one-horsepower donkey cart.  Forget about making out in the back seat, too. (Oh, yeah, nobody does that anymore, do they?) But it sure is amazing to see neat technology made possible by millions of corporate scoots being used in what seems like a sensible approach.

The HCCI concept is powered by a 2.2-liter Ecotec engine that makes 180hp and 170lb-ft of torque. It features a central direct-injection system, has variable valve lift on both the intake and exhaust sides, dual electric camshaft phasers and individual cylinder pressure transducers to control the combustion as well as deliver a smooth transition between combustion modes.  A very sophisticated controller, using cylinder pressure sensors and GM-developed control algorithms, manages the HCCI combustion process, as well as the transition between HCCI combustion and conventional spark-ignition combustion.

HCCI, along with other enabling advanced technologies, approaches the engine efficiency benefit of a diesel, but without expensive lean NOx after-treatment systems. Rather, this engine’s efficiency lies in reduced pumping losses, being able to burn fuel faster and at lower temperatures, and reducing the heat energy lost during the combustion process, all the while releasing less carbon dioxide. The HCCI engine ignites a mixture of fuel and air by compressing it in the cylinder. Unlike a spark ignition gas engine or diesel engine, HCCI produces a low-temperature, flameless release of energy throughout the entire combustion chamber. All of the fuel in the chamber is burned simultaneously.  

A traditional combustion event occurs at the left side of both images. Fuel enters via the intake port and a spark plug ignites the air and fuel mixture.  The "burn" of the mixture projects from the spark and the flame progresses throughout the combustion chamber. An HCCI combustion event occurs at the right side of both images. Fuel enters via an injector located in the combustion chamber.  The air/fuel mixture ignites through heat caused by compression and without a spark.  The lower temperature "burn" of the mixture is simultaneous and even throughout the combustion chamber.  Traditional spark ignition is used to start the engine cold to generate heat within the cylinders and quickly head up the exhaust catalyst and enable HCCI operation.