[Denny]

This seems promising, though not revolutionary. GM will be producing two forms of direct injecton gasoline engines next year, and they promise substantial fuel savings, about 134 gallons per year on a small SUV used for 15,000 miles. (Well, assuming GM is producing anything, that is.)

The mystery to me is that this idea seems so basic, its just a mimic of diesel technology, so why has it not been applied to gasoline engines before? But, kudos to GM all the same, maybe the public will get some payback for the retooling bailout.

See article at Detroit Free Press

" An advanced engine technology will improve fuel consumption and power for three key vehicles General Motors will unveil at the North American international Auto Show in Detroit next month.
Direct fuel injection will push EPA fuel economy ratings for the new 2010 Chevrolet Equinox compact crossover to at least 30 m.p.g. on the highway, GM will promise today when it reveals two new engines that use the system. Direct injection saves fuel and improves power by allowing very precise control of how and when fuel is injected into the engine's cylinders.

"It's a win-win for the consumer," said Jim Hall, managing director of 2953 Analytics, a Birmingham forecasting firm.

The 2010 Equinox will come with either a 2.4-liter four-cylinder engine or a 3.0-liter V6. GM hasn't revealed fuel economy figures for the V6, but the engine will produce 255 horsepower, an impressive output for a small V6. The V6 also is to be available in the Buick Lacrosse and Cadillac SRX.

By 2010, GM says it will offer direct-injection engines in 38 vehicles around the world. The company expects to sell 500,000 direct-injection gasoline engines in 2009. GM estimates the all-new 2010 Equinox will save its owners $270 to $400 a year.
The Equinox, LaCrosse midsize sedan and SRX crossover all will feature DI engines and six-speed automatic transmissions. Combined with other technologies that GM already uses, like variable-valve timing and cylinder deactivation, GM says the net result will be that the vehicles it builds in 2009 will use 700 million gallons of gasoline less over their lifetimes than their 2008 counterparts.

The 2.4-liter four-cylinder engine is part of GM's Ecotec global family of four-cylinder engines.

It will come from GM's Spring Hill, Tenn., plant. The 3.0-liter V6, which comes from the same family as the 3.6-liter V6 used in the Cadillac CTS, Chevrolet Traverse and other models, is to be produced in Ramos Arizpe, Mexico, and St. Catharines, Ontario."

[mos6507]

Is anyone really assuming that GM is even going to be around next year?

[Andy]

This is not really new technology. Mitsubishi has had GDI (Gasoline Direct Injection) engines for some time now.

[cipi604]

GM is so dead.

[frankthetank]

They could've went one step further and just made a 4 cylinder diesel.

[mgibbons19]

And this is different from EFI because that injects the fuel into the throttle body?

[drew]

Yes, quite. Throttle body injection is as close to a carburetor as you can get. Direct gasoline injection is as close to diesel as you can go. In between are multipoint F.I., and sequential multi point F.I.. Each step closer to direct injection gives better control over the fuel-air mixture prior to combustion, hence better fuel economy.

Drew

[SteinarN]

The point with gasoline direct injection (GDI) is not the exact control of the fuel/air mixture.

It is that when a normal throttled gasoline engine is running lightly loaded the throttling valve is only slightly open allowing only a small amount of air to enter the cylinders while when the GDI engine is running slightly loaded it has a much more open throttling valve allowing much more air to enter the cylinders. The small amount of gasoline is then injected directly into the cylinders at the end of the compression stroke, like a diesel engine, and the spark plug ignites this combustible mix. Unlike a normal gasoline engine, in a GDI engine there is a large amount of unused oxygen left in the cylinders after the gasoline is combusted when the engine is running in a low load condition.

The advantage with this solution is that the engine acheives a better efficiency solely due to more air entering the cylinders at low load settings.

It exists mathematical/physical laws regarding the maximum obtainable efficiency in relation to the compresion ratio and the amount of air entering the cylinders. Higher compression ratio and more air/higher intake manifold pressure gives a higher obtainable efficiency.

The diesel engine has still significant higher compression ratio and is thus still superior the GDI engine in efficiency both in full load and low load operating conditions. The difference in low load operating conditions is not as bad between a GDI and a diesel engine as it is between a normal gasoline engine and a diesel.

[mgibbons19]

cool. thanks for the info.

[TommyJefferson]

Higher compression ratio and more air/higher intake manifold pressure gives a higher obtainable efficiency.

Interesting summary. Thanks.

[cephalotus]

The mystery to me is that this idea seems so basic, its just a mimic of diesel technology, so why has it not been applied to gasoline engines before? ..

This technology is called Diesotto from Daimler.

[Frank]

Actually I would think that most of the efficiency increases are due to reduced pumping losses (that's why diesels are more efficient at idle/low-speed.) If the throttle can be opened more it takes less energy to pull air into the engine. Air/fuel ratio is probably controlled pretty much as it is with modern EFI engines, trying to obtain the best compromise between various exhaust pollutants, but I'm sure this would probably be more efficient. Modern diesels can use multiple pulses of fuel for each combustion cycle.

There are other schemes to obtain the same advantages: BMW for instance was working on a variable-lift engine so that no throttle at all was needed.

Regardless, this is nice technology. ICE's will always be limited by Carnot though...

[The_Toecutter]

Much greater fuel savings could have been realized by focusing on aerodynamics...

Higher compression ratio and more air/higher intake manifold pressure gives a higher obtainable efficiency.

Interesting summary. Thanks.

Take a look at "Carnot's Equation" and it is quite clear how this works.

[bencole]

The mystery to me is that this idea seems so basic, its just a mimic of diesel technology, so why has it not been applied to gasoline engines before?

Economics of mass production I would think.

Many GM engines have a history of being junk due to cost cutting measures.

But, kudos to GM all the same, maybe the public will get some payback for the retooling bailout.

Doubtful

[bencole]

They could've went one step further and just made a 4 cylinder diesel.

Small diesel cars seem to be more of a European thing.

Unfortunately GM's last foray into building diesel engines for cars was a complete disaster, a failure of such proportions that they have never tried again. For some reason they seem to have a problem with the basics of 100 year old plus technology.


http://www.autoweek.com/apps/pbcs.dll/a ... /505130704

[Pablo2079]

Ford launched Direct Injection this year... coupled with it's new ecoboost (twin turbo) tech.

http://blogs.edmunds.com/greencaradvisor/2008/01/ford-to-introduce-fuel-saving-direct-injection-engines.html

The EcoBoost engines, which run on regular unleaded fuel, work by injecting highly pressurized fuel (yellow in illustration) directly into each cylinder instead of vaporizing and mixing it with air (blue) in an intake port. Direct injection, used by many diesel engines and by some competitors in a variety of gasoline engines, permits the fuel to be used more efficiently.

By combining that technology with turbocharging -- in which exhaust gases (red) are used to power a turbine that compresses air going into the intake, increasing engine output by boosting the amount of air in the air-fuel mix -- –the EcoBoost engine delivers far more power and fuel economy than a conventional gas engine.

Ford says it will couple the EcoBoost technology with other features including electronic power-assisted steering, lightweight frame and body materials, six-speed transmissions and improved aerodynamics.

[kanman]

Huh? GDI is so 1997.

I can't believe this is being Marketed by US car manufacturers as anything remotely new. Mitsubishi were the first ('97 Carisma) but by 2003 even Ford introduced a GDI offering in Europe (1.8 Mondeo).

Are you guys still trundling round with live axles, drum brakes and recirculating ball steering?

[timmac]

Huh? GDI is so 1997.

I can't believe this is being Marketed by US car manufacturers as anything remotely new. Mitsubishi were the first ('97 Carisma) but by 2003 even Ford introduced a GDI offering in Europe (1.8 Mondeo).

Are you guys still trundling round with live axles, drum brakes and recirculating ball steering?

You bet baby, we here in America want heavy steel, V-8 power, 4 barrels and fat tires, if it don't bark its tires shifting into 2nd or 3rd than it ain't cool..