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Keep an Eye on HCCI

In the majority of scenarios for building sustainable mobility (decreasing emissions, increasing fuel efficiency, weaning from oil), there is a substantial short- to medium-term emphasis on advanced conventional technologies.


One of the promising engine technologies that has emerged over the past few years is called HCCI -- Homogeneous Charge Compression Ignition. To the right is a diagram comparing HCCI with spark ignition (your basic gasoline engine) and compression ignition (diesel). (Click to enlarge. Source.)

HCCI relies upon a very lean (high proportion of air to fuel) and well-mixed (Homogeneous) air-fuel mixture (Charge) that is compressed (Compression) until it autoignites (Ignition). The resulting spontaneous burn produces a flameless energy release in a large zone almost simultaneously -- very different than the spark/gasoline burn or the compression/diesel burn.

HCCI is a very efficient engine without the nasty NOx or PM emissions of a diesel. It can operate using a variety of fuels -- gasoline, diesel, natural gas, biofuels, hydrogen.

However, there are barriers to overcome -- such as reducing the amount of unburned hydrocarbons and figuring out the complex contorl mechanism. The latter is first a matter of understanding the dynamics of the chemistry and then figuring out how to best control it in different situations, with different fuels, etc. There is a great deal of research focus on HCCI, however, because the potential benefit in many different use cases is high. The Society of Automtoive Engineers (SAE) is hosting a special two-day HCCI symposium this August.

Some Resources:

  • FreedomCAR & Vehicle Technologies

  • HCCI Lab at UC Berkeley



Does this remind anyone else of a compression-ignition model aeroplane engine?

Lloyd Weaver

We are just promoting a new invention on HCCI.

The web site is , please click on "New Inventions" to see the HCCI
engine material. There is another link under "New Inventions" HCCI (Click here to see image)
to pull up drawings on engine operation.


Ganesh Dalvi


Ganesh Dalvi


roddy Mackenzie

Dear Sirs,

HCCI has been solved. See Full range from 0.2 - 0.9 stoichiometric. Pressure boosting capable to 4 Bar. Sub millisecond fuel vapourisation with no air. Total vapourisation and no wetting whatsoever.

Complete ignition timing control from + - 5 degrees top dead centre. Knock control through partitioned combustion chamber.

Machine has been running about 35 hours.

Any ideas on how to sell it?


Excellent... It was very useful for me n i recommended this site to my friends too!!!!

Raymond Bushnell

There is a company in Oregon called Vapor Fuel Technologies that has a patented system that utilizes a form of HCCI they call spark initiated autoignition. The fuel is fully vaporized and mixed with heated air prior to combustion. This process can be used with standard engines at normal compression ratios. The result is an increase of over 30% in fuel economy. The tests were run at a certified independent test laboratory. There is much more information available at their website

khanin das

actually i go through your information regarding HCCI but i got some doubts regarding its efficiency, its performance and its air fuel ratio.i want to know how we can control its ignition. i am really very grateful to know about HCCI from your paper.

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