There have been anomalous claims of engine efficiency over the years that related to better ways of burning fuel. I think these were unwitting efforts at HCCI and I am glad to see this finally making the main stream. I had thought for years that we were missing the point in the way our engines ran but I never quite managed to get my mind around the issue until I read about Honda's Active Radical Combustion process. I had experienced something like this combustion process as a kid on a 2-stroke motorcycle but just thought it was a hot spot in the head triggering the combustion. I cut the ignition and the engine continued to run quite well. When similar happened to old man Honda he had the brilliant insight to investigate further.
Here is an interesting engine that the inventor claimed ran on a detonation combustion cycle many years ago. I don't think the claims were ever demonstrated in front of a third party. If it ran as claimed at the efficiency claimed it was a fore runner of the modern HCCI engine. It ran with restricted exhaust and was manually leaned out to what was called detonation after it was running. I think it may well may have been HCCI on some occasions.
http://bourke-engine.com/
Here is a more sanguine analysis of this engine.
http://en.wikipedia.org/wiki/Bourke_engine
Here is a modern attempt at this combustion process. I have talked to this inventor. He is a very decent and intelligent person. He is a rational experimenter and generally quite practical. He has achieved very lean burn but there is little reason to believe this engine will achieve any commercial success.
http://www.rad-cam.com/_wsn/page2.html
There used to be a patent application that gave considerable detail of the engine. It dwelled at TDC for about 18 degrees. It used a clever cam arrangement rather than the Scotch yoke. It ran a little higher head temperature and cooler exhaust. I don't think he ever made any claim of any specific fuel consumption. It could be brought to idle RPM at WOT by leaning out the mixture. This was simply a working prototype. I suggested to him at the time that it looked like HCCI but he did not respond to that point. Anyway it is a very cute engine. If he had just ran normal combustion the engine seemed very practical to me. He knew he had to go to MPFI for even fuel distribution and I think he ran out of money at about that point. It is darn cute anyway.
On the subject of HCCI I have long thought that Smokey Yunick's "Hot vapor engine" was burning fuel in a process similar to HCCI. Most conventional engine engineers said it should detonate it self to destruction. For some reason it did not. The fuel economy claims were on par with HCCI combustion also. As a college student I called up Smokey and he talked to me for 15-20 minutes about that engine. This was a few years after it had fallen out of the news. I asked how he was controlling detonation and he insisted there was no secret other than uniform cylinder head temp. He spend a great deal of effort to keep the intake and exhaust sides of the combustion chamber within about 15 degrees of each other as I recall. I asked specifically if he was using EGR to control detonation and the response was generally negative. In any case he got darn good mileage.
http://schou.dk/hvce/
Linear Mode
