http://money.cnn.com/2007/08/23/auto...ion=2007082415

The article makes this new technology look great.....utill you read the last few lines. I'll stick to my CTD for now!

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Like this is some thing new, I grew upin Florida and we had all kinds of cars that would diesel on gas and my great grandfathers Bonneville would even drive and speed up with the key off, It was it first time in Florida and the heat made it hell the shut that off, we had to choke the air from it to stop it.

 

15% over conventional gas engines....and only to 55??? Just another great idea from GM.

 

I don't understand why it would cut off at 55. If it is truly diesel style than it should be direct injection just like a diesel that fires under load. My guess is that it is the same as when some car companies were saying they were working on direct injection a few years ago, but it wasn't like a diesel at all. It sprayed the fuel directly into the cylinder, but it didn't do it while the cylinder was fireing like a diesel and it still had a throttle plate. When it was under full load it would still spray on the compression stroke, there by eliminating the benefits of dry compression that diesels have. (increased compression and no need of a throttle plate) They were just doing it because under low loads they could lean the cylnder out by spraying the correct mixture just by the plug leaving a majority of the cylinder lean. If they are trying to get rid of the throttle plate I can see how that would get them the 15% increase. Think about it, if we open up our intake and exhaust most people see an increase in mpg, that is because the engine has to work less to intake and expel air.If they can get rid of the throttle plate instead of having to pull against a vacuum they could get closer to atmospheric pressure, now if they turbo it then they can get positive pressure all the time.If it is truly diesel style then theyshould be able tojack up the compression which should net them more than 15% between eliminating the throttle plate and the increased thermal efficiencies that come with higher compression. The reason gas is so hard on a diesel engine is because it burns to fast and brings the peak cylinder pressure up to fast, not to mention it is hard on the fuel system. With the new injectors that are firing multiple events I don't see why they couldn't make a true diesel style variation that would use a lot of little events to keep the pressure more even instead of something that can't even drive the speed limits.

 

http://www.autobloggreen.com/2007/07...rman-for-hcci/

It looks like Mercedes is way ahead of GM on this one.

 

HCCI might turn out to be economically viable mod
but I personally like this alternative way of making
gasoline engines MUCH more efficient:

http://www.technologyreview.com/Energy/18304/page1/

MIT's idea also uses direct injection like HCCI
but they make use of ethanol as an octane improver in the best possible way.
Right now the USA is using ethanol in fuel the WORST possible way.