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What is HCCI, and What Does it Mean for Efficiency

Has GM struck gold, 30 years later?

HCCI, which stands for Homogeneous Charge Compression Ignition, is currently under development at General Motors. Under the watch of Paul Najt, who worked on the technology during his days as a PhD researcher, HCCI is coming to the forefront of GM’s work on eco-friendly gasoline technology. The technology was put on the shelf years ago, but has made a comeback with several important improvements and discount viagra united kingdom a promise from GM to make it viable for use in passenger vehicles in the near future.

I recently had a chance to try out this new technology in a working Saturn Aura. You can check out my post-ride review of the technology. But right now we're going to dive in and talk about exactly what HICCI is, and how it works.

What is HCCI?
At its most basic level, HCCI combines the buy viagra without prescription in usa best properties of diesel and gasoline engines into one. Gasoline engines use spark ignition, whereas diesels are compression ignition, meaning that instead of using spark plugs to ignite the air-fuel mixture within the cylinder they use the pressure of the piston to buy levitra soft compress the mixture, creating heat and ignition. Because compression ignition is inherently more efficient, diesel engines are predisposed to good fuel economy, but at the cost of high NOx emissions. Gasoline engines, on the other hand, are less fuel efficient, but are also much cleaner in terms of NOx emissions.


HCCI partially bridges this gap by creating a gasoline engine where compression ignition is possible. This gives the engine both the pfizer viagra uk operation and feel of a diesel, but without many of beta blockers and levitra the associated pollution problems. GM was careful to say, however, that they were not planning on a convergence between diesel and gasoline engines, but rather that they were working to make each as efficient as possible, since both are already well-suited for particular modes of operation (i.e. diesels make better large trucks, but gasoline engines are a better fit for sedans).

There are several new tech advances that have come together to produce the modern, 4-cylinder, 2.2-liter, 180 HP engine that I test drove. This includes direction injection, a dual electrical cam phaser (as opposed to hydraulic), 2-step valve lift, and combustion pressure sensors. The combustion pressure sensors are extremely important because they allow the engine to make minute adjustments on the fly, which is necessary because HCCI is extremely sensitive to mail order viagra uk operating conditions. These combustion pressure sensors have fallen in price rapidly, part of what makes an HCCI engine more commercially viable now compared to even a dozen years ago.

Another important advance is the ability to run in HCCI mode in low-load and idle conditions. The biggest thing making diesel and HCCI-equipped gasoline technologies different is that HCCI engines are not always using compression ignition. Because of noise, vibration, and technical issues, engines can only operate in HCCI mode in low-load situations. This range has recently been improved, allowing HCCI operation in idle as well, but the Aura I test drove could only maintain HCCI up to about 55 MPH, at which point it would switch back to standard ignition (SI) mode. Similarly, the Aura would enter SI mode during brisk, and usually stayed in HCCI mode when cruising.

Part of the excitement over HCCI technology is that it offers very little negatives for all the positives that are promised. Of course, not all promises and expectations are likely to be met, but for now the technology seems like one of the best things GM has to offer.

As I already mentioned, the HCCI-equipped engine that I test drove was able to canadian pharmacy cialis prescription cram 180 HP into a (relatively) small, 4-cylinder, 2.2-liter form factor. Because HCCI is inherently more efficient, it not only results in improved fuel economy, but also increased power output. As far as fuel economy is concerned, there likely have not been any real-world or EPA-like tests done, but GM is quoting a modest 15% increase in gas mileage. I say modest not because I’m unimpressed with the number, but because new technologies often come with wild claims about how quickly they will solve the world’s problems, and this does not seem to be the case here.

On top of the improved efficiency, HCCI mode operates at a lower temperature than diesel, below the range where harmful NOx pollutants are created, making the engine extremely low-emission. Emissions are reduced across the board when in HCCI mode compared to bother diesel and gasoline engines. HCCI mode is also possible with ethanol blends up to E85, making the engine fit in well with GM’s near-term plan for increased E85 use.

Perhaps the most salient upside of HCCI technology is the cost / benefit ratio it offers. Though GM isn’t talking specifics yet, I was told that it would be cheaper than current hybrid and us overnight cialis diesel technology, putting it within range of the average consumer and positioning it to make the best price generic levitra largest impact on fuel consumption and air pollution.

Definitely exciting technology to watch. Hop on over to my post-test drive review to learn more on how it performs in the real world.

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Comments (21)Add Comment
no thanks
written by james, May 13, 2008
Another SUPER complex engine (compare just the picture of it to an electric motor) to keep the consumer tied to gasoline, gas stations, repair and service regimens, and all the associated costs. No way! The time has come for much simpler, smarter, efficient, totally clean and ultimately super sustainable machines to run us around. I am just waiting for someone to create an ultracapacitor that will hold lots of electricity and make the electric car fall into place.
I'm not interested in this GM Frankenstein.
written by Adam, May 13, 2008
This was a great idea 30 years ago but not anymore. Plus, the general is unable to build reliable standard gasoline engines so I have absolutely no doubt this more complex engine will be full of problems.
written by Ralph, May 13, 2008
It still is a great idea. I say bring it on line.
written by Jay Tee, May 13, 2008
It may be a good transitional technology before we are all driving electrics.
Its not much more complicated; the technology was waiting for better computer control and better sensors.
Now GM needs to work on getting much more than a 15% fuel savings out of it.
written by Eco, May 13, 2008
There are millions of cars on the road with pathetically inefficient engines. It would be nice to rip them out and replace them with more efficient ones. 15 percent is not much, but maybe they can continue to improve it, get it up to 30 percent.
Diesel correction
written by Jesse, May 13, 2008
This article states that the diesel engine compresses the mixture which then ignites. This not true because there is no mixture in a diesel engine. Only air is compressed, the air is highly compressed and gets very hot. Then the fuel is sprayed on this compressed hot air where it combusts. Although this is only a subtle correction is very important because the diesel engine would not operate as described above.
written by dialtone, May 13, 2008
something even better than this - check out Coates Spherical Rotary Valve
just look at the picture & you can see it is much simpler & a better efficiency gain also
Diesels - trucks / Gas - cars?
written by Harry, May 14, 2008
Why are diesel engines better for trucks than cars?
Truck engines are better for trucks than cars, sure. ;)
I'd always thought that diesel engines, take longer to warm up than petrol, so are better if you make more long journeys than quick trips.
Not impressed...
written by Joe, May 14, 2008
I must agree, I am not impressed. While the generic levitra mastercard statement that some new technologies are boasting unrealistic improvements, this "modest" 15% is loathsome.

I don't believe the technology currently available today is the answer, nor do I believe the answer is close. However, I do (slightly) commend GM on trying.

I am also NOT in favor of discount cialis online ethanol, nor GM moving towards E85. I've read reports claiming that the amount of Fossil Fuels used during the production of ethanol are equal to the ethanol produced (disclaimer: I am not a fuel specializing scientist, nor did I conduct my own tests). I, personally, like my corn roasted on the grill.
written by EV, May 14, 2008
Why are diesel engines better for trucks than cars?

Diesel engines produce a higher torque at a lower RPM than gasoline engines. That means that for hauling 10 tons, a diesel engine can operate at 2,000 RPM while most gasoline engines would have to operate at 5,000 RPM. Having to operate at such a higher RPM causes a lot of wear and tear and stress on the engine and make it wear out faster. The diesel, however, is operating at a nice 'low' RPM and will continue to do so. That is why trucks use diesel.

Cars in the US generally use gasoline as it is easier to make a gas engine comply with the environmental regulations (see post in the other HCCI article). Additionally, a gas engine generally has a better 'pick up' (acceleration) than a diesel does. This is generally more sought after in cars than trucks.
I am also NOT in favor of ethanol, nor GM moving towards E85. I've read reports claiming that the amount of Fossil Fuels used during the production of ethanol are equal to the ethanol produced (disclaimer: I am not a fuel specializing scientist, nor did I conduct my own tests). I, personally, like my corn roasted on the grill.

Correction. You are not in favor of CORN Ethanol. Look back several news stories and you will find one on a Cellulose Ethanol plant in Georgia. That plant will use wood chips and shaving to create ethanol. Something that will NOT affect the food supply or need fertilizer. There is also research being done to make ethanol out of other non-food plant stocks that is much more efficient that making it from corn.

Problem formulation is the key to viagra ed solving a problem. If you do not figure out what the right problem is, you will most likely make the situation worse.
Heck yes!
written by Troy, May 15, 2008
This sounds like it could be a short-term solution for our gas consumption and environmental problems. Maybe this technology could even be coupled with hybrid technology. Seeing as it pulled 180 horsepower out of a 2.2L 4 cylinder (my 3.1L V6 only gets 160), we could be looking at some very powerful hybrids.

As for the engine being complicated, all the complication I see here is the addition of some pressure sensors. That's not all that bad considering how complex ordinary modern engines are. Besides, mechanics need money too! Hehe.
Another skeptical
written by Luciano, May 15, 2008
With so many technologies out there (heck, there are even cars moved by compressed air...), it's amazing how we're so stuck on oil.

I agree that things take a long time to change due to the whole infrastructure and changes in paradigms, but isn't it time for us to move forward once and for all? It's like we're shooting in every direction and not choosing any...

On the other hand, it is nice to see a new technology for combustion engines. I'll take 15% any day of the week, especially when you multiply it by millions of vehicles on the roads every day.
written by Pao Chi Pien, December 14, 2008
Homogeneous charge autoignition combustion produces homogeous products of combustion without uburned hydrocarbon (UHC). The whole charge burns simutaneously in autoignition combustion without hot zone which promots NOx formation, and has higher effective expansion ratio to increase the fuel efficiency. It is a different combustion process and has nothing common with gasoline engine or diesel engine.
Natural Gas
written by Rod, February 18, 2009
Electric drive has distinct advantages over fossil fuel, fewer lubricants & longer service intervals. Couple this with a environment friendly fuel, natural gas and a mechanically simple (and light) generator system, gas turbine, and you may be able to build an efficient,easy to maintain, and environmentally friendly vehicle requiring no oil imports.
written by John, March 02, 2009
This is a great next step in increasing efficiency. I have to ask what is it going to take to generate all the electricity that is going to be needed for all these "environmentally friendly" electric vehicles? Also how much is electricity going to cost for everybody when we go electric? Interested to see if the can you buy ultram over the counter Tata "aircar" isn't a more elegant way of using electricity to power a car. But all of this electric stuff is pie in the sky until we have the electric generation & transmission capacity to charge thousands nay millions of car.
Hey James!
written by Patrick, May 01, 2009
I think that yout comment on electric cars is misleading. I have an electrical back ground and I have to ask "what do you think happens when a battery has lost it's charging life?" I will tell you that yes it might get recycled properly 40% of the time, but I will tell you that the rest of the time it goes to a land fill in China where poor children take these batteries and computer parts and viagra 20 try to extract the precious metals out of them and throw the rest in the river only to pollute the river. A better alternative is to have car that run on Hydrogen.
written by Brian, May 02, 2009
Actually Honda had a HCCI engine in the 1970's Accord.
I read that in Car & Driver or Motor Trend awhile back.
Of course the technology is much better now.
written by hermit, July 17, 2009
Everyone falls into the same trap in thinking electrics solve all problems. Did it ever occur to anyone that there are not enough copper reserves in all the world in order to build all these electric motors? Gasoline engines are 90% iron and recyclable. Electric motors have copper, plastic insulation, steel that must be separated to recycle. And what about the resources to build electric motors compared to a simple foundry for a gas engine block. Complexity=energy....
Old is better than new in some ways
written by Ethan, January 10, 2011
Funny thing about this technology is that it's hyper-complex with modern fuel injection and emissions equipment, which is the federal requirement. It's amazingly simple when carbureted, but that's not in line with regulations. Curburetion isn't usually as clean as fuel injection, but it CAN be... alas... only in test environments and not for practical use.
only 15%?
written by danwat1234, June 15, 2012
I applaud VW and GM in developing HCCI engines, it may be a good alternative to Atkinson cycle engines in that they have a better power curve and thus aren't limited to Hybrids vehicles as Atkinson cycle engines are.
Perhaps HCCI can be more efficient than an Atkinson-miller cycle engine, who knows.

One thing I know is that diesel and HCCI engines are efficient enough. Extended range EVs with HCCI or diesel engines would be superb.
HCCI - Dynamically Variable stroke Technology
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HCCI is a winner but it needs a practical, no cams, extra shafts extra pistons design to be reliable. Varitech has the solution to try it cialis online pharmacy no prescription dynamically variable stroke technology-it simply removes the crankshaft and installs a unit. The stroke can be varied while it is running from zero to maximum. contact us for more info.

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