The success of HCCI development, to date, is tempered by challenges that must be overcome before it hits the primetime of production. Control of the combustion process over the wide range of operating conditions experienced in everyday driving is the greatest challenge, because unlike a conventional-ignition engine, HCCI's combustion is not controlled by precisely timed spark events. Ensuring auto ignition at extreme temperatures and in the thinner air of high altitudes are the tallest hurdles to overcome.
While GM used a Saturn Aura as a test bed for the new engine technology, we're pretty darn sure that a Saturn won't be the first vehicle from General Motors to benefit from the technology given that the brand is up for sale.
We'll bring you a full drive report if we ever get the chance to slide behind the wheel.