COMPRESSION IGNITION is, by convention, strictly the domain of diesels. The sparkplug-less ignition of a fuel-air mixture does however hold some promise when applied to petrol engines, and General Motors is moving forward with its development of a workable compression-ignited petrol powertrain.
Dubbed the HCCI (or Homogenous Charge Compression Ignition) engine, GM's experimental powerplant works on a phenomenon which normally spells mechanical doom for conventional petrol motors.
Compression ignition, or 'dieseling' can wreak havoc on the pistons, rings, rods and bearings of a regular petrol-powered engine, but in GM's HCCI mill it's the gateway to fewer emissions and greater fuel economy.
The American automaker recently demonstrated a prototype version of the HCCI engine, and the technology certainly is promising. Think 15 percent more fuel economy, less energy wasted in pumping losses, lower combustion temperatures and less carbon-dioxide emissions than a spark-ignition engine.
"HCCI delivers enhanced fuel savings without sacrificing the performance consumers have come to expect," said Prof. Dr. Uwe Grebe, executive director for GM Powertrain Advanced Engineering.
"It is a great example of how GM is developing advanced engine technology for consumers that squeezes more miles per gallon of gas and reduces emissions."
There are some inherent challenges, however. Because compression ignition is affected by air density, GM has yet to perfect the HCCI's operation in extreme temperatures and at high altitudes. The system won't self-ignite when the engine is cold either, so a conventional sparkplug is used to keep it running until it reaches operating temperature.
"GM?s global HCCI team is working to refine the technology in the wide range of driving conditions experienced around the globe," said Dr. Grebe.
"By combining HCCI with other advanced gasoline engine and control technologies, we can deliver a good fuel savings value for consumers."
The prototype is an inline four-cylinder motor, but the HCCI concept will work just as well on a six or eight-cylinder engine. The technology is still some distance from the production line, but it's good to see that despite being neck-deep in all sorts of financial strife, GM is still continuing to innovate.