There has been a reoccurring debate over the merits of diesel vehicles versus hybrid ones. Both technologies help to increase fuel economy; however, people tend to be convinced that the one or the other is the only solution to these problems.
Now GM finally is preparing to lay these criticisms to rest with potentially the first compression-ignited gas engines to see rigorous real world testing, in preparation of market entry.
In order to understand why this is so significant, a discussion of engines is in order. Diesel engines typically have two advantages over their gasoline burning counterparts. The first is direct injection. Traditional gas engines inject fuel into an intake, and the air-gas mix is then sucked into chamber, compressed, and finally ignited. Diesel engines put it directly into the combustion chamber, a more efficient process. This problem has already been tackled by Ford (EcoBoost), GM and many others, and direct-injection gas engines will soon be all over the market.
The second diesel advantage is compression ignition. In a diesel engine, the compression of the gas/air mix triggers ignition, and the compression causes the combustion to be evenly distributed. In a traditional gasoline engine, compression is limited by design so less-efficient spark ignition must be used. This problem has yet to be solved in a production model.
GM's HCCI (homogenous charge compression ignition) four-cylinder engine unveiled at the company's research and development center this week may be the first engine to bring compression to the world of gas engines. In early testing the engine deliver 15 percent better fuel economy and much lower NOx gas and CO2 emissions.
Uwe Grebe, GM's executive director of powertrain advanced engineering, says that the new engine greatly reduces these toxic gases. He says that the technology can easily "be applied to many engines, including four- , six- and eight-cylinder engines."
The secret to the new engine is temperature control. Typically an engine runs at 3,800 degrees Fahrenheit, but the new engine runs from 0 to 60 mph and from idle to 3,000 rpm at 2,900 degrees Fahrenheit (ignition temperature). This means that there are fewer pollutants, and compression can be used to ignite the fuel without risking damage to the engine. Essentially this yields a gas-burning engine that runs as clean and efficiently as a diesel.
Vijay Ramappan, staff engineer for calibration, states, "From zero to 60, this engine can run completely in HCCI mode and basically work like a diesel."
GM is not revealing when the engine might see production deployments, or if it will utilize GM's direct injection gas technology to offer even greater benefits, a likely move. Whenever the engine does see the market, though, it would make a dynamite partner to a hybrid powertrain, possibly delivering a gasoline-sipping engine with potential performance well north of 100 mpg in small cars.
quote: I'm not sure how they can switch to spark ignition unless they can also lower the compression ratio somehow.
quote: Sorry for the tangent, but are there DT moderators that come along and change the ratings of posts?
quote: so it pushing for innovations in diesel tech would probably be the best way to go for companies that want user and anti-GW friendly cars.
quote: Fixed it for you. Diesel cars are great, but produce significantly more particule pollution (cause Cancer, Resporitory Issue, etc) and well as significantly more NOx and other real pollutants that directly harm the enviroment.
quote: New engines are solving the emission issue, but they extra costs involved might be used on a gasoline engine based car in ways that make the total "enviromental" impact the same (I am not sure C02 really should be considered, but hey that the way politics/public opinion is headed)
quote: diesel's redline are determined by exhaust gas temperature, and is usually around 3000RPM. quote: this is incorect, i own a diesel car, and red line is little over 4600 rpm. about 10 years a go we hade ford ecort diesel and its redline was over 5500 rpm
quote: this is incorect, i own a diesel car, and red line is little over 4600 rpm. about 10 years a go we hade ford ecort diesel and its redline was over 5500 rpm
quote: Well, your car engine sucks up the most gas during acceleration. Once you reach cruising speeds, the engine is much more efficient.
quote: manuals get better fuel economy than automatics due to less drivetrain loss and less weight. CVTs don't have as much drivetrain loss as automatics but still weigh more than manuals. And are far more complicated. Manuals are the cheapest, simplest transmissions.
quote: How do you like shifting in rush hour traffic, stop and go, driving in cities.
quote: Your idea of "connection" is nonsense...
quote: Clue: Only an idiot goes into a turn fast enough they try to make a transmission gear slow the engine, instead of braking to the right speed. I don't misunderstand, rather I am not an idiot like you who risks themselves and others.
quote: You've contradicted yourself. On the one hand you say manual is more efficient then on the other you say it isn't because of the gear ratios used, so what it "could" be isn't what it actually is.
quote: It was entirely correct, but idiots don't like truth.
quote: Untrue, thanks to the fuel efficiency mandates they are placing automatic shift points where they achieve near maximum efficiency.
quote: While it is true an auto can upshift much sooner than any person could in a manual
quote: There you go again, just chanting mantras. Don't you have a life?
quote: almost all the posters here have no love for cars.
quote: I read that as more of exasperated support than as a recommendation to stop.
quote: Traditional gas engines inject fuel into a prechamber where the burn starts, whereas diesel engines put it directly into the combustion chamber, a more efficient process.
quote: The second diesel advantage is compression ignition. In a diesel engine, the compression heats the air to a sufficient temperature for ignition, and the compression causes the combustion to be evenly distributed. In a traditional gasoline engine, compression is limited by design so less-efficient spark ignition must be used. This problem has yet to be solved in a production model.
quote: Why is GDI better than port injection? Unlike port injection where fuel is sprayed behind the intake valve, GDI reduces intake manifold inefficiencies that limit air and fuel mixing, and allow fuel to evaporate outside the cylinder. The lack of a throttle plate in some engines also eliminates pumping losses. The direct injection fuel spray cools the cylinder, allowing higher compression ratios. The cylinder charge is localized and thoroughly mixed, bringing tiny fuel droplets nose to nose with oxygen for faster, more efficient burning.
quote: Not sure how you would throttle it without a valve/plate, though
quote: Like I've said BMW doesn't use a throttle plate, but still throttles the air flow (which still introducing pumping loss, but BMW says less so than a plate).
quote: Fuel pressure doesn't always vary on a regular fuel injected engine
quote: Right now diesel is cheaper than premium here.
quote: Don't know why you got rated down here. The price of diesel in the US varies wildly. Where I live it's a little cheaper than 87 octane.
quote: Not everywhere and that's my point. Rate me down if you want but it's not cheaper everywhere.
quote: If the goal is to maintain roads, then since a gallon of diesel has a higher amount of energy than gasoline, it will place a relatively higher amount of road load than the gallon of gasoline. Thus, Diesel should be taxed at a slightly higher rate than gasoline.
quote: Correlating the amount of energy a gallon of diesel has vs. that of gasoline to the amount of load on the road for taxation purposes is absurd. You're saying that a tiny diesel car puts more of a load on the road than the same size gasoline car? No.
quote: I think diesel hasn't caught on over here because diesel fuel has higher taxes and therefore costs more than gas.
quote: They buy the most cars yet its a state known for hating them. Oh the irony.
quote: They buy the most cars yet its a state known for hating them. Oh the irony.
quote: Love it how its been two days since our latest industry crippling emissions standards
quote: But Pelosi will have her private military jet to fly between her home and DC at our expense.
quote: If I recall, reducing the particle emissions on a diesel wasn't exactly cheap.
quote: like 22:1 or higher vs 8.5-11:1 for gas
quote: As far as 2 plugs per cylinder, Dodge has been doing that since 2003 on the Hemi(at least my parents Durango has 2 plugs per cylinder). Not sure how many other cars do this as well though.
quote: Can existing diesel engines use gas?
quote: In early testing the engine deliver 15 percent better fuel economy and much lower NOx gas and CO2 emissions.Uwe Grebe, GM's executive director of powertrain advanced engineering, says that the new engine greatly reduces these toxic gases.
quote: Great if you live in Canada, probably not good if you live in Mexico. :)