Small Engine, Big Mileage, Same Power? Just Say “GDI”

Okay, now the carmakers say they get it. Americans want better fuel economy, and they want it now. And just to make sure that message was received, last December Congress passed a law that requires fleet mileage of 35 mpg by 2020.

So how does the industry plan to get there? Despite what many green consumers might like to think, we won’t all be driving electric cars—or even hybrids—next year. Hybrids may be a much larger portion of the market by 2015—GM exec Bob Lutz says it may be 30 percent, certainly higher than the current 2.5 percent—but large numbers of cars between now and 2020 will still be fueled by plain old gasoline.

Within a couple of years, however, they will be much, much more efficient with that gas. And one way they’ll do it is with a new technology that’s about to spread like kudzu: smaller engines with gasoline direct injection, or “GDI.”

Rather than mixing gasoline with air in an intake manifold before it’s sucked into the combustion chamber, a GDI engine’s fuel injectors squirt the gas directly into the cylinder. Modern electronics now allow very, very precise calculation and metering of each separate injection. And remember, if the engine is turning at 3,000 rpm, there are more than 10 such injections every second.

Older engine electronics simply weren’t fast enough to look at all the data about everything happening in the engine, and then calculate the right amount of fuel for each cylinder and have it squirted in on time. And those injectors were too pricey to use when gasoline was $2 a gallon or less.

But injection is just half the picture. GDI engines are smaller than regular ones, but they put out the same power because many (though not all) are also turbocharged. A turbo is a small pump, driven by exhaust gases, that packs more air into each cylinder. That allows more fuel to be used, producing greater power—but from a much smaller engine than a non-turbo with the same power.

The combination of direct injection and turbocharging are similar to techniques used to make modern passenger diesels smaller, smoother, more powerful, and cleaner than earlier versions. Now gasoline engines will travel the same path.

Building on their diesel experience, European carmakers already sell non-turbocharged GDI engines in many home-market cars. Now they’re starting to appear in export models too; Volkswagen offers a 200-hp, 2.0-liter GDI engine in its new Tiguan small SUV, for instance. But GDI will be a tidal wave, and it’s coming fast.

Ford calls its GDI system EcoBoost, using it to produce the power of a V8 from its 3.5-liter V6 engine. According to Dan Kapp, Ford’s director of power train research and advance engineering, it will provide 15 or 20 percent better fuel economy. EcoBoost will first appear in the 2010 Lincoln MKS luxury sedan, then it’ll move into Ford’s large pickup trucks. That engine, by the way, actually produces more torque (340 ft-lbs versus 310) than today’s 4.6-liter Ford V8. Ford recently said it will offer EcoBoost engines on more than 80 percent of its lineup by 2012.

GM, on the other hand, will use GDI more as the Europeans do. The company’s first GDI engine for the US will be a “Family Zero” 1.4-liter turbocharged GDI for the Chevrolet Cruze, a global subcompact to be introduced at the Paris Motor Show in October. That car will be built from 2010 in Lordstown, Ohio, for the US market, replacing the Cobalt for 2011. GM has estimated a fuel economy of 45 mpg, a substantial increase over the Cobalt’s 25/36 ratings when fitted with the most modest engine, a 2.2-liter Ecotec.

And, it turns out, a far more glamorous vehicle than the Cruze will also use the same engine. While the Chevrolet Volt concept vehicle contained a European 1.0-liter, three-cylinder gasoline engine, press reports now say the production version in late 2010 will use the same engine as the Cruze. GM has filed paperwork to build an engine plant of half a million square feet in Flint, Mich., to produce 1.4-liter GDI engines for the Cruze—and, apparently, for the Volt as well. That motor, however, will use standard induction, according to GM spokesperson Rob Peterson—contradicting earlier reports that the Volt’s engine would be a turbo as well.

In the next five years, in fact, turbocharger manufacturer Honeywell projects that globally, engines with turbos will grow from 30 to 38 percent of the total by 2013.


  • steved28

    This is all well and good, but it misses the point of any hybrid based vehicle, recover lost energy. Every time you slow your car, you throw energy away to heat. I don’t care if you recover that energy in a battery, hydraulics, or a flywheel, but it’s a massive amount of energy when multiplied by millions of vehicle.

    The other “no brainer” is not to use energy when you are sitting still. MPG doesn’t mean a thing when you are stopped at a red light. We have to start focusing on all the energy we simply throw away or do not put to any use. This includes our vehicles, homes, workplaces etc.

    I made a small change this year and installed an on demand hot water heater in my home, shutting down my oil fed burner and 60 gallons of “stand by” hot water. My electric bill went up $20 per month, I saved $720 in oil over the summer.

  • tw8s

    This is a good FIRST step for the world if it can be quickly applied to the large vehicle market where it would give twice the reduction of gallons per year of driving compared to the econo car market. This technology installed in an 18mpg class vehicle would save 100 to 200 gallons per year, while the new Colbalt owner would save 50 to 100 gallons per year.

  • Anonymous

    I wouldn’t call it a FIRST step, but it’s yet another good step (one of many). As with all things, it is better to work slowly and steadily implementing small incremental improvements than to put all your eggs in one basket looking for that One Big Breakthrough.

    PHEVs are going to be easier to realize because automakers developed HEVs first. Full electric vehicles will be easier to realize (not to mention more reliable, cheaper, and better quality) for having been implemented as an incremental change to a PHEV rather than a brand new ground-up vehicle. Look at all the trouble Tesla has had even getting a car with a six figure price tag to market. The first EV brought to market by Toyota or GM will certainly not be as “sexy” as the Tesla, and we’ll have to wait a while longer for it. But it will be within the reach of more car buyers than the Tesla, by several orders of magnitude.

  • Boom Boom

    The US is so far behind on the hybrid front, we may never get out in the lead, but if US Auto can get engines on the market which beat the Japanese competition by 10-20% in MPG first, then we might have a chance to rise up. Hybrids are great (and I say this as a driver of one), but we also need technology that can be more quickly deployed to the entire fleet. (Rapid growth in Hybrid production runs into battery supply issues, etc.) I do agree with TW8 that the focus should be on big and medium size cars as much or more than on small cars.

  • Sidney

    The point of a hybrid is not to recover lost energy, that is one of the benefits of the hybrid system. The point of a hybrid system is to combine the best features of two different propulsion methods, resulting in a system that is more efficient than when using either of the two propulsion methods independently. Current hybrids use a internal combustion engine as one of the propulsion methods. GDI will make the ICE more efficient, which in turn will make the hybrid system more efficient. It will also make conventional automobiles which use internal combustion engines as the only source of propulsion, more efficient. GDI is nothing new. Diesels have been using this for quite some time.

  • CT_Jake

    The other unfortunate trend with manufacturers (especailly the D3) is to also increase the horsepower unnescessarily with these units so that some of the advantage is lost. These dummies can’t seem to get over their horsepower hangup: “Mines’ bigger than yours!”

  • steved28

    “The point of a hybrid is not to recover lost energy…”

    Of course it is! If the battery just worked off the ICE alone the gains would be far less.

  • Sidney

    I disagree. If recovering lost energy is “the point” of a hybrid system, then, by your logic, a hybrid system without regenerative braking is no longer a hybrid system. Of course that would be incorrect. Today’s hybrid systems allow one to make use of energy that would otherwise be dissapated as heat by using a technique called regenerative braking. (the energy is not actually lost but converted to electrical energy instead of energy in the form of heat) The hybird system would be less efficient without this, but would still be a hybrid system.
    Perhaps I should explain what “the point” actually is. A vehicle’s ICE needs to produce a lot of torque to get it moving. Small gas engines use less fuel but produce smaller amounts of torque, resulting in slower acceleration. At constant velocity (cruise), relatively little power and torque is needed to keep a vehicle moving. A hybrid system or, combination of gas and electric motors, allows one to take advantage of the best points of both powerplants. Electric motors can produce a lot of torque at low rpms for great acceleration so you don’t need a big ICE. This results in better gas mileage at cruise because your running with a smaller engine than would otherwise be acceptable for all around performance.

  • steved28

    Yes, I agree that technically “hybrid” means the joining of two different drives. But one of those drive systems in a gas/electric hybrid is the “electric” side. And a major component of that side is recouping lost energy. Otherwise the electric side of the hybrid equation would not be worth the effort.

    In other words, if you separate the two drive systems, and look at one as a BEV, regeneration is a major component. It may not be the point of a hybrid system, but it is such a major component that one could argue it is one of the top reasons, if not the top reason, for the increase in fuel mileage.

    A gas/electric hybrid without regen braking would totally rely on the ICE for all energy produced, one way or another. (as you clearly understand from your writings) And would be hardly worth the small gains. Perhaps I should have said the point of the hybrid is efficiency, and that requires regenerative braking to recover lost energy. Same conclusion for me.

  • Armand

    Good points….and nice job on efficiency!

  • Bryce

    That 1.4L Turbo sounds beautiful to me. : ) with numbers like 45 mpg, it would seem that the engine will be effectively tuned towards fuel economy, but it is also reported to return HP numbers around 120-140 putting it right in line with 2.2L Ecotec in the Cobalts today, while blowing it (and other competitors) out of the water in fuel economy. It will also be way cheaper than a hybrid given that it will not use batteries and and all the other stuff necesary for that. A money saver for an urban student just like me. Sounds beautiful. : )

  • Sidney

    “It may not be the point of a hybrid system, but it is such a major component that one could argue it is one of the top reasons, if not the top reason, for the increase in fuel mileage.”

    Really? How do you know that?
    Yes, one could argue that and I think I will.

    I’m an electrical engineer, asic and embedded design. I attended a college here in CA where every year, my aero-mechanical engineering dept. created a hybrid vehicle from a standard vehicle that was donated by a major auto manufacturer. I have two Prius vehicles. One, my wife drives. I can’t touch that one. The other I have probed, modified, instrumented, etc. I was curious just how much efficiency was gained with regenerative braking, so, I found a way to disable it. After ~500 miles of driving with regen enabled, I averaged 48.3 mpg. ~500 miles of driving with regen disabled yielded 46.8 mpg. 3.1055901% decrease in indicated mileage per gallon. Its not a major component of the hybrid system.

    Most of the efficiency of the Prius is gained by the use of a small gas engine which uses what is called an Atkinson cycle. This cycle differs from the more typical Otto cycle in that it’s operation is closer to an ideal adiabatic process. That combined with the ability to cut the engine off when stopped or going downhill, along with a very low drag coefficient are the top reasons for the increase in fuel mileage.

  • Gary E Fassauer

    It,s good to read the more possitive coments from cocerned individuals and it’s great to hear from more interested people. soound like we will over come these times.

  • 40ford

    CT_Jake, you are RIGHT ON! I drive an Escape Hybrid and with it’s relatively small 4 banger, it has plenty of power yet gets me over 30 mpg all the time. Not bad for an SUV. A lot of hybrids out there don’t deserve to be called “hybrids”, with their big engines and electric motors to “give even more power to the wheels”. BS
    And shame on Ford for not promoting the hybrid more. I’m constantly amazed at how many people don’t know Ford HAS a hybrid! Or exactly what a hybrid is. The public is NOT well informed about the technology. Someone once asked me if my Escape used “special gas”!

  • Mar4k

    I don’t get these “one or the other” arguments. It seems to me that they were inspired by GM executive Bob Lutz’s comment near the beginning of the article, and only show that he is not a visionary (which wasn’t news to me in the first place). GDI is good because it allows smaller engines to power larger vehicles. The technologies that are used to produce hybrid vehicles are good for the same reason. Why does the marketplace necessarily have to choose one or the other? Can’t they alll be used in different kinds of vehicles with the net result of saving fuel? And is there some reason why all these technologies couldn’t be combined in some vehicles to save even more?

  • richard schumacher

    As Sidney’s experiment shows, only a few percent of the benefit of a hybrid comes from regenerative braking (recovering energy during decelleration). Most of the fuel savings comes from load-leveling: that is, the internal combustion engine is sized only for the average power required and not for the maximum power. This allows it to be much smaller than otherwise because the electric motor does much of the work of launching the car from a stop. Regenerative braking and engine-shutdown are smaller added benefits, but they come essentially for free as all of the necessary mechanisms are already in place.

    A GDI hybrid should indeed do better than either technology alone, but of course it would be more expensive.

  • water damage chicago

    35 mpg BY 2020? Absolute rubbish. That technology ALREADY exists! In fact, this technology has existed for many, many years, but these automakers keep milking the consumers. Every year up until 2020, they will increase the fuel efficiency on their cars by just a couple or a few miles to keep milking us.

  • BMW

    Great informative material and i agree with GDI engine’s fuel injectors squirt the gas directly into the cylinder. Modern electronics now allow very, very precise calculation and metering of each separate injection. And remember, if the engine is turning at 3,000 rpm, there are more than 10 such injections every second.

  • Kitchen Design

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  • Corky

    I love the whole idea but I don’t like congress mandating the auto industry regarding when and what mpg vehicles need to by a certain time. I say stay out of it.

  • dentist essex

    it is really cool idea, hope this will help to come out from the ecomoic crisis and will bring totally new way, Cheers,

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