• May 25th 2009 at 6:58PM
  • 37
Since our first encounter with General Motors' HCCI (homogeneous charge compression ignition) engines in August 2007, the powertrain research engineers at the GM Tech Center in Warren, MI have continued plugging away at the technology, trying to turn it into a marketable reality. The basic premise of compression ignition is simple. Based on the Ideal gas law (PV=nRT), if you decrease the volume of a particular quantity of air, the temperature rises to the point where fuel will spontaneously combust.

The hard part is controlling the pressure, temperature and air/fuel mixtures precisely enough to manage that combustion without causing excess noise and engine damage. When we first tried the HCCI prototypes a couple of years ago, the engines had a fairly narrow band of HCCI operation with the engine running in basic spark ignition mode the rest of the time. Thanks to a newly developed mixed-mode HCCI feature and external EGR, the engines can now run in HCCI from idle all the way to 60 mph!

We had a chance to drive a Saturn Aura with an HCCI engine based on the 2.2-liter EcoTec four-cylinder around the streets near the Tech Center. The engine ran smoothly and transitions between HCCI and spark ignition really couldn't be felt. The only indication of a transition was a slight ringing sound over the first couple of power cycles after transition.

The basic hardware for a production HCCI engine is in place now, with the only new piece of hardware being a combustion chamber pressure sensor. GM is continuing to work on the control software to make this a robust system and even adapting the homogeneous charge and pressure sensors to diesel engines to reduce NOx emissions. The HCCI engine achieves about a 15% improvement in fuel efficiency compared to a similar spark ignition engine at a much lower cost than a hybrid. GM hopes to have HCCI engines in production in about five years.

[Source: Green Fuels Forecast]



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    • 1 Second Ago
  • 37 Comments
      • 6 Years Ago
      I think that people are missing the point here. Did people consider that an HCCI engine could be put INTO a hybrid powertrain?
      • 6 Years Ago
      "Hybrids may be simply mechanically speaking, but the controls and software are very complex."

      And the point? Semiconductors are maintenance free and they are more reliable than moving mechanical parts.

      "regenerative braking is very annoying, makes it a pain to modulate deceleration to the point that it is probably dangerous in certain cases."

      You probably experienced the traction control kicked in. The crappy OEM tires and owner pumping the air pressure well above the recommended PSI amplified this issue. This has been improved in the 2010 Prius. ECU no longer manage the TC but passed that responsibility to the "Brake Control Unit". Better tires are equipped and they are wider as well.

      "HCCI would be more simple from a ownership perspective because of no need for a large battery. Not having that battery saves weight."

      A full hybrid may have 99 pounds HV battery pack but it carries 40 lbs less gasoline. A full hybrid also has a smaller 12V lead acid battery, saving another 30 lbs so you are only looking at 30 lbs extra. The ability of recharge the battery while slowing down the car outweighs the 30 lbs.

      HCCI engine alone can not capture braking energy. It can not shut down the engine. It will need a mechanical transmission.

      I think it would be ideal to have HCCI ICE in a full hybrid or plug-in hybrid. The cost of the extra combustion pressure sensor should cancel out with the lack of 4 spark plugs. Plus, it would be maintenance free (no need to change the plugs at 120k miles).
      • 6 Years Ago
      You know, Hybrids are all fine and dandy until you realize your back seat passengers are basically sitting on a bomb. There is a reason that Engines are not in the passenger compartment (or under it). Until Batteries are small enough to place in the trunk or under the hood I'd stay away from anything that uses them (Hybrids like the Prius, and electric cars like the Volt).

      Any advancement to the ICE that allows me to avoid a battery and the dangers of them is a great thing.

      Don't believe how dangerous the batteries are, go look at what a service tech has to do to verify that the system is "off" before he can work on it.
        • 6 Years Ago
        Sitting on a bomb? Um, no, that isn't where the gas tank is located.

        As for the NiMH hybrid battery, it has never been known to catch fire or explode, unlike the H2 emitted from the lead acid starter batteries in your car. Moreover, in my Prius, the batteries are located in the trunk.

        Of course there are safety precautions while working with high voltage batteries, just as there are elaborate safety precautions for working on fuel lines. Gasoline is highly flammable and the vapors are explosive.

        Really, Justin, you should learn not to keep repeating silly hybrid myths.
        • 6 Years Ago
        Justin:

        > You know, Hybrids are all fine and dandy until you
        > realize your back seat passengers are basically sitting
        > on a bomb.

        How many batteries in those million+ hybrid vehicles in service ever exploded?


        > Don't believe how dangerous the batteries are,
        > go look at what a service tech has to do to verify
        > that the system is "off" before he can work on it.

        I bet they have to care much less than firefighters when dealing with a wreck of a car equipped with airbags:

        http://www.youtube.com/watch?v=b1Qj75pbl8o

        Every car now has two large airbags on board which, unlike batteries, are designed to explode violently and do explode occasionally. Yet you don't complain about that. Do you avoid cars with airbags?


        > There is a reason that Engines are not in the passenger
        > compartment (or under it). Until Batteries are small enough
        > to place in the trunk or under the hood I'd stay away from
        > anything that uses them (Hybrids like the Prius, and electric
        > cars like the Volt).

        Batteries in Prii and other hybrids (except S400) are all under the boot, not in the passanger compartment.
      • 6 Years Ago
      Simply stated, I always have, and always will support GM. They have all the ingenuity and innovations that any import company can offer, and will regain their leadership in the automotive society.
      • 6 Years Ago
      Holy smokes batman GM wants to give ICE more complicated parts. Soon Lada will have a more reliable record then a joe blow GM.
      harlanx6
      • 6 Years Ago
      I hope GM is still around in 5 years.
      • 6 Years Ago
      One stupid question : I believe its a 6 speed auto coupled with HCCI was able to achieve 0 - 60 mph, Cant this be scaled using a 8 speed transmission with HCCI to 100mph than using mixed mode ?


        • 6 Years Ago
        This 8-speed would have to have an increased spread to make it up to that speed at the lower HCCI rpms, and then the car would have to be making sufficient horsepower to get up to that speed. Since HCCI is RPM limited, not speed limited, and knowing how far my own car tops out at in its highest gear with a bigger torque-ier engine around 2500-2600 rpm (just above 90 mph with the torque converter locked in 4th), it probably just does not have the horsepower to hit 100 mph. This is assuming similar Cd and max torque around 180 lbs-ft at 3000 rpm (just over 100 hp).
        • 6 Years Ago
        Then again, I could be wrong if HCCI can run well above 3000 rpm (think up to 4k) and the gearing was just right. But that might compromise real-world efficiency.
        • 6 Years Ago
        If it's heavily constrained by RPMs this is one of those cases where a CVT would make a really big impact in keeping in the right rev range.
      Atul
      • 6 Years Ago
      Hybrids may be simply mechanically speaking, but the controls and software are very complex. I've driven the first 2 generation Priuses and let me tell you that the regenerative braking is very annoying, makes it a pain to modulate deceleration to the point that it is probably dangerous in certain cases.

      I wish I could drive other hybrids to see how other companies have handled it. I'm not against hybrids, but HCCI would be more simple from a ownership perspective because of no need for a large battery. Not having that battery saves weight.

      I'm not sure who it was but he questioned that I actually drove the car. My mom's Saab 9-3 Linear that I described above has 50,000 miles on it and it has averaged 28+ mpg with half city driving. I used to own it and put on the first 40,000 miles. Keep in mind that the car weighs 3,200-3,200 lbs has simple turbo technology and is the safest car of its size that can be purchased. It's a 2003 design with 2003 technology and I still got 38 mpg on the highway last night.
        • 6 Years Ago
        @Atul
        I've driven the first 2 generation Priuses and let me tell you that the regenerative braking is very annoying, makes it a pain to modulate deceleration to the point that it is probably dangerous in certain cases.

        My girlfriend owns a 2rd generation Prius with 100k miles on it, and I drive it regularly. The regenerative braking works very nicely when you're in D(rive). It's a a lot touchier when the shifter is in (B)rake mode, but B isn't really intended for normal driving. The B mode for descending steep hills and other situations where you might use engine-braking in a manual transmission car. (She never uses B, since she learned to drive on an automatic, and holding your foot lightly on the brake pedal has the a similar effect and does not wear out the brake pads.)

        Also, having driven the 2nd generation Prius on ice and in a variety of slippery winter conditions, the traction control and anti-lock brake systems both work *very* well. It will reduce power to keep the wheels from slipping during acceleration. It will yaw the car in conditions where it seems like it should just understeer. I normally drive so that these systems aren't necessary, but I have tested them and been very impressed with the results. The Prius is far better in the snow and ice than my Ford Ranger, just so long as it has the ground clearance to move at all.

        The Prius may not be for you! There's no reason why you in particular should like or want a Prius -- it's a small passenger car that looks like an Enterprise shuttlecraft, and not everyone needs that. It's not not a sports car, and it's not for hauling heavy loads. There are dozens of reasons that the Prius might not be the right car for you... But regardless of whether meets your needs, your taste, or your philosophy, the Prius really is an excellently engineered little car.

        I sure hope that GM produces a small car meets the needs of a Prius driver better than the Prius! But that hasn't happened yet -- all of GM's hybrids and BAS cars are too big for our taste, and none of them have crossed that magic 50mpg barrier. I sure hope that the Volt will be the car that makes the Prius obsolete, but the Volt won't arrive at my local Chevy dealer here in the midwest for at least 18 months, even if it does make it to production.
      • 6 Years Ago
      Yeah, now they are trying hard to make more efficient cars. Too late.

      I don't have a death wish for G.M, but I don't think it's healthy to have a company that big having such influence on so many workers. We need to diversify and have more companies competing based on value.

      Plus, who's the old geezer responsible for all these boring designs? Even if these cars become more efficient, they remain unattractive to most people.

      - Nick -
        • 6 Years Ago
        "SKY and Solstice versus ??? "

        EXACTLY. How much development did they pour into that car only to find what everyone else already knew, there is no market for it.
        • 6 Years Ago
        yes, GM has made small efficient cars -- but the styling suggested that it's just a stopgap car that you can drive until you can afford one of GM's "real" vehicles.

        Contrast the Cobalt with, say, the Mini Cooper or the Prius and you'll see what I'm getting at. The Mini Cooper, VW Jetta , and the Prius have enough features and character to compete directly with larger vehicles for a certain buyer. Both the Jetta and Mini cooper will attract the kind of buyer who wants a zippy little car that's still practical enough to be a daily driver. The Prius attracts technology buyers and environmentalists with the hybrid drivetrain and its spaceship looks. Compared to that, what does the Cobalt offer?

        Another data point would be the Ford Focus. Look at the pre-2008 ford Focus... I drove a rental 2001 Ford Focus for two weeks in 2001 (after my 1989 Ford Tempo had been rear-ended), and I wasn't convinced that it was any better than my old beater with either looks, performance, or features. Compare that to the 2008-2009 Ford Focus -- it's probably the same car, but some subtle changes to the styling make them look like a car that you don't have to be poor to drive, and I've been seeing an awful lot of them on the road. The Focus is likely to be even more competitive after the Euro Focus will be sold in the US in a year or two.

        So, yes, GM has made efficient cars over the last 5 years or so -- but they didn't target them at buyers who have a choice about what car to buy. So, those of us who want a small car just because we like them are very likely to end up driving a foreign car. I hope this will change with the Volt and the Cruze, but time will tell.
        Atul
        • 6 Years Ago
        Nick P.

        GM has made efficient cars for years, but you're too stubborn to want to believe it. And trust me GM's vehicles are a lot more attractive than Honda's and Toyota's are. Malibu and Aura versus Camry and Accord? SKY and Solstice versus ??? Full size trucks from GM versus the ugly Toyotas? It's no contest.
      Atul
      • 6 Years Ago
      And people say GM doesn't do anything to advance technology for improved fuel economy. It would be great to see GM master HCCI before other companies and provide comparable effiiciency to heavy, complex hybrid powertrains.

      Speaking of GM and fuel efficiency, I drove my mom's 2004 Saab 9-3 Linear 2.0 t 5-spd automatic, and with less than 10 mph diagonal winds and a 300 ft elevation drop over 28 trip miles around 65 mph on the highway at 65 degrees, the car read 40.1 mpg!!! Even if the trip computer is off by 5%, that's still 38 mpg. Unbelievable but true. (I was using Shell mid-grade gas.) I can't imagine what the car would have gotten on a warmer day. What if it had a 6 speed automatic?
        • 6 Years Ago
        @Atul
        @downtoearth:

        "> comparable effiiciency

        The efficiency will not be comparable because HCCI shaves of 18% while hybridization manages 27-30%."

        Dude, keep drinking that Kool-Aid. Where'd you get those numbers? 27-30% saved? Seriously...?

        Combined Fuel Economy (according to EPA)
        Lexus GS350 - 10.7L/100km
        Lexus GS450h - 10.2L/100km

        That's less than 5%.
        • 6 Years Ago
        @Atul
        Kevin:

        > Dude, keep drinking that Kool-Aid. Where'd you get those numbers?

        > Combined Fuel Economy (according to EPA)
        > Lexus GS350 - 10.7L/100km
        > Lexus GS450h - 10.2L/100km

        Why are you comparing a performance oriented hybrid vs its ordinary rival without considering the performance?

        From Lexus.com:
        GS350 0-60 = 5.7 sec
        GS450h 0-60 = 5.2 sec

        Doesn't sound like much but here's the better thing:

        " but for all that it sprinted to 60 mph in 5.5 seconds and covered the quarter-mile in 14.1 seconds at 103 mph. This was a shade quicker than the M45, as well as the GS430, and more important, the 450h posted the best 30-to-50 and 50-to-70 times in the group, performance that made it impressive in back-road passing maneuvers."

        Source: http://www.caranddriver.com/reviews/comparison_test/sedans/2007_bmw_550i_vs_infiniti_m45_lexus_gs450h_m_b_e550_comparison_test+page-2.html

        So the GS450h can top some V8 (!) sedans in terms of 0-60 acceleration and tops all the compared V8 ones (Infiniti M45, BMW 550i, Mercedes E550) in terms of passing/in gear acceleration.

        Funny you failed to mention that.


        > 27-30% saved? Seriously...?

        Yes. Let's prove it.

        Nissan Altima Hybrid:
        0-60 in 7.5 sec
        EPA Comb = 34mpg = 6.91 l/100km
        EPA used shared (28+8 samples)= 34mpg = 6.91 l/100km

        VW Passat 2.0 TFSI:
        0-60 in 7.7 sec
        EPA Comb = 23 mpg = 10.22 l/100km (48% more than Altima)
        EPA user shared (4 samples) = 25.3 mpg = 9.29 l/100km (34.4% more than Altima)

        I took two cars that offer the same performance, the same size, the same body type and shape, the same drivetrain type (FWD automatic) and took even real life estimates to ensure a realistic comparison.

        I also picked the most efficient ordinary gasoline setup - a downscaled engine with a turbocharger and a direct injection.

        I can continue on and on with the Camry vs Camry Hybrid, the Prius vs Corolla but in no other case so many aspects will be matched. For instance the Camry Hybrid is significantly faster than a 4-banger one but slower than a V6-one. Prius on the other hand employs additional means of saving fuel (tires, shape) and is also a big larger than a Corolla.
        • 6 Years Ago
        @Atul
        UH2L:

        > comparable effiiciency

        The efficiency will not be comparable because HCCI shaves of 18% while hybridization manages 27-30%.


        > to heavy, complex hybrid powertrains.

        I think some education about hybrid drivetrains may help. You'll realize that these are the SIMPLEST drivetrains in the market now. Hybrid Synergy Drive requires:
        - neither an automated (dual) clutch nor a lockable torque converter
        - neither a complex gearbox with multiple mechanically/hydraulically actuated gearmesh and multiplate wet clutches as in case of dual clutch gearboxes or automatics

        Hybrid Synergy Drive also employs possibly the simplest engine in the market yet one of the most efficient one as far as brake specific fuel consumption is concerned. These Atkinson cycle powerplants require no turbocharging, no direct injection, no variable valve timing, no additional exhaust treatment components.

        What HSD adds are components with no moving parts (a battery, an inverter) and electric motors that are rather simple things, aren't they?


        > Malibu and Aura versus Camry and Accord? SKY
        > and Solstice versus ??? Full size trucks from GM
        > versus the ugly Toyotas? It's no contest.

        It's cool to share opinions but I rather prefer facts.


        > Speaking of GM and fuel efficiency, I drove my mom's
        > 2004 Saab 9-3 Linear 2.0 t 5-spd automatic, and with
        > less than 10 mph diagonal winds and a 300 ft elevation
        > drop over 28 trip

        It's even cooler you drove something somewhere or maybe you didn't but the real life observed fuel economy of this car is 24-26 mpg.

        People get it. Edmunds got it. EPA rating is 21 mpg.

        http://www.edmunds.com/insideline/do/Drives/FullTests/articleId=79822/pageId=36085
        http://fueleconomy.gov/mpg/MPG.do?action=mpgData&vehicleID=19656&browser=true&details=on

        The car does 0-60 in 8.1 sec. Brilliant, the Camry Hybrid is 0.5 slower and people get 36.5 mpg out of it. Do you have anything to add as far as fuel economy is concerned?

        http://fueleconomy.gov/mpg/MPG.do?action=browseList2&make=Toyota&model=Camry%20Hybrid

        Oh, I nearly forgot. Nissan Altima Hybrid with the HSD tuned for performance does 0-60 in 7.5 sec and returns 34 mpg.
      • 6 Years Ago
      "I think some education about hybrid drivetrains may help. You'll realize that these are the SIMPLEST drivetrains in the market now. "

      Well said Downtoearth..
      • 6 Years Ago
      When it goes into production, will they then put it into a 600 hp engine, instead of a 100 hp engine to deliver excellent gas mileage?

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