Green Car Congress reports that GM is road testing a Saturn Aura equipped with a homogeneous charge compression ignition (HCCI) engine. HCCI technology compresses a lean air-fuel mixture in the cylinder, which ignites without spark plugs, creating low-temperature, flameless combustion. GM says HCCI combustion reduces NOX and particulate emissions and offers 15 percent better fuel efficiency. The 2.2-liter modified ECOTEC engine is set up to use traditional spark ignition when starting, driving over 55mph and other low-temperature or high-load circumstances. It switches to HCCI mode for most driving. The modified mill makes 180hp and 170 lb/ft of torque, with additional help from direct injection, variable valve lift, dual electric camshaft phasers and individual cylinder pressure transducers to "control the combustion as well as deliver a smooth transition between combustion modes." Props to GM for developing technology which doesn't require them to reinvent the wheel battery, but it'll be a while before HCCI is ready for prime time. That said, direct injection– as seen on the new Porsche Cayenne and other, more prosaic VeeDubs– had a rocky start.
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Several other automakers are working with HCCI including Mercedes and Honda. The other two are trying to eliminate the need for retaining the electric ignition component and have a normal redline. Supposedly the difficulty with HCCI engines is the powerband is smaller and the engine has trouble running at lower and higher rpm. If they can perfect this and get similar gains to diesel using gasoline then all the better. Gasoline runs cleaner in particulate emissions but since it uses more gas than diesel has higher carbon dioxide and water vapor emissions.
In sparkling contrast to some of their other “technology to save the world” GM has a reasonable launch estimate (2015 IIRC) on this.
But then the media isn’t all hot for it. Go figure.
On the other hand, in many road tests (don’t give me EPA estimates, puhleeez) they seem to lag 10-15% behind the mileage of the best in class.
So yippee.
Yes, I am not pumped about GM. Boo hoo.
Bunter
PS-I’ll be out for a week so if I don’t rebutt a rebuttal, I’m not stiffing any of you.
Tootles.
I’m curious, what issues have Vee Dub had with direct injection?
If this is compression ignition of a lean mixture, much like a Diesel cycle, then how do they lower the NOx? I thought NOx formed best during high temperature lean conditions.
I think they’re burning gasoline. Combustion is flameless… so lower temps and I bet that’s why NOx are not formed.
I believe it’s from the fact that the combustion in a compression engine is much more controlled and complete versus gas spark ignition engines. It’s that unburnt portion that is the most noxious.
It will be interesting as to how this pans out. This reminds me of what Ford was trying to do in the late 70’s. Does anybody recall PROCCO? This stood for PROgrammed COMbustion. The idea was to emulate the combustion dynamics of a diesel engine but with gasoline. IIRC it worked in a lab but there was no way to put the needed computer power into a car in 1979. The drop in fuel prices after the ’79-81 stagflation ended the program; the engines were allegedly destroyed. Also, I have to ask this question: Does anybody at TTAC recall “Shell of the Future”. This was unleaded gas in 1972 sold out of a baby blue pump. Anybody?
Flameless combustion? Are you sure about that? Or is it just “sparkless” combustion?
So that 15% increase in efficiency will guarantee 15% larger vehicles?
How about 15% BETTER vehicles?
FWIW I think the technology is pretty cool. Any little thing helps.
Good point. No such thing as “flameless combustion.” Credible?
Same as “dry water?”
Good for them. So why the bashing anyhow?
Seems like regardless of the financial woes, they’re still trying to produce.
Guess they don’t read the blogs!
I think what that means is that there is not a flame front moving through the cylinder—it all burns at the same time. You could always, you know, look it up. ;)