HCCI

It doesn't really go here, but since in discussions of the future volt the possibility of hcci came up, I thought I would post here.

Bosch Hard At Work On Sparkless Ignition HCCI Engine

First the similarities, the hcci prototype is built on the same ecotec engine that is rumored to be in the Cadillac ELR version of voltec at the end of next year.

Normally aspirated HCCI should combust cooler than spark ignition. That would make it less efficient without turbo charging but lower in NOx and soot.

Add the energy returned by the turbo and low load power becomes both cleaner and more efficient. HCCI still needs help at load, so the gm system switches to Spark ignition at higher loads. The gm system also adds a pressure sensor and a super charging system to get pressure up high enough to combust.

 

Thanks. It appears that delphi is working on this on a DOE grant with hyundai. Since GM demoed this tech so many years ago, I wonder what the hold up is on getting it in cars.
GM's HCCI engines now run from idle to 60 mph!

That was in 2009. My guess is the tech - turbo, di, valve timing, egr gets most of the efficiency improvements. After that HCCI may not add much. I would love to know what the efficiency of the engines are. The carnot efficiency must be lower than an engine like skyactiv. What would make HCCI more efficient is if the turbo returned more of the power in the exhaust to feed the hcci compressed air. The question then are the turbos and extra sensors and software worth the extra money. They may not be if that multi-mode high compression engine can supply enough power at 2L or less. This would leave hcci only making sense if the application called for more than 160hp or needs to be downsized for size.

HCCI is most efficient at low loads, and reduces NOx and particulate emissions compared to diesel. It may be cooled egr as even the gen III prius does keeps these emissions under control. That leaves efficiency.

HCCI seems to be a lower polluting mode of lean burn's stratified charge. I would love to be able to compare efficiency between stratified charge which can be much more easily contriolled by timing and injection choice, and hcci.

HCCI seems to be best mated with the hyundai or bmw hybrid system with a small flywheel motor. This can eliminate the very low power spot, where hcci is inefficient and makes the software easier. HCCI may especially be helpful in SUV and truck engines, where the added cost is a small percentage, but peak power needs are much higher than cruzing power.

 

That does make it seem like you would want to do it on say a 1.4L turbo engine with a 20kw flywheel motor like on the vw jetta hybrid to smooth transitions and allow high speed glides. Perhaps the 15kw motor in the malibu eco is enough to smooth the transition though. Sell it with the 2L hcci as a performance eco model. Now that would be a niche car to experiment with.

 

cool. Do you have any details?