The Gasoline Engine Is Hearing Knock at Door

The process is simple. Take 15 parts air, one part gasoline, turn them into a compressed mist in a sealed chamber, and add a spark. It’s been that way for 100 years.

Whether the underlying design of Gottlieb Daimler’s internal combustion engine will be around for another 100 years remains to be seen.

Environmentalists locked to the conventional electric vehicle, such as General Motors’ EV1, certainly doubt it. They have not been satisfied by development of low and ultra-low emissions vehicles, nor by fuel injection and electronic engine management systems that have created cleaner, more efficient gasoline engines. Even some internal combustion evangelists preaching the gospel of “step on the gas and it goes” have acknowledged a global need for a power source that does not pollute, does not burn holes in the ozone, will not promote global warming or exhaust our fossil fuel supplies.

Hence a continuing focus, by researchers, engineers, and manufacturers on battery technology to perfect conventional electric vehicles--but also new attention to viable alternatives such as fuel cells, natural gas power and hybrid vehicles.

And Dr. G’s mailbag indicates that public confusion reigns. Must hybrid gasoline-electric vehicles be plugged in overnight? [No.] Is diesel power anywhere in the picture? [Maybe.] What does direct injection mean? [See below.]

New emissions and mileage standards and a push by environmentalists to extend those rules to sport-utility vehicles, pickup trucks and minivans open the field to the next generation of engine design.

The hybrid engine, which is new technology, and direct injection, which is already used in diesel engines, are close to or being used in production vehicles.

The hybrid power plant, which uses a smaller gasoline engine in tandem with an electric motor-generator, is in Honda Motor Co.’s V V, a 2000 model coupe due in the U.S. this fall, and Toyota Motor Corp.’s Prius, also due out late this year.

The V V uses a 1.0-liter, three-cylinder ultra-lean-burn gasoline engine, assisted by the electric motor when more power is needed. The car’s batteries are recharged through regenerative braking.

The result, says Honda spokesman Art Garner, is a vehicle with very high mileage and very low emissions, but performance is in line with a standard 1.5-liter Civic. However, the similarity ends there.

The V V achieves its mileage, emissions rating and performance not only from the new-age power plant but also from aerodynamics and low weight, achieved through the use of aluminum and plastic for frame and body parts. The car weighs less than 2,000 pounds but will meet safety standards, Honda says.

Although Honda already has an electric car, the EV Plus minivan, owner feedback indicates that the limited range remains a major stumbling block, Garner says.

But with a fuel efficiency of more than 70 miles per gallon, the V V would have a range of about 700 miles, depending on how large a gas tank is used in production models.

“The car is a technological showcase for Honda,” Garner said. “It combines the performance that customers would expect from this class of vehicle, plus very high efficiency and low emissions.”

Emissions low enough, he notes, to meet California’s new super-ultra-low emission regulations, which will be required of all automobiles by 2007.

The Prius carries a $17,000 price tag in Japan, but that is believed to be about half of what it costs to make the vehicle.

As for Honda’s V V, Garner says it won’t be a big profit maker for Honda at a projected price of $20,000.

“It’s more of an investment,” he said. “Some of the things that we feature in the V V will find their way into other products.”

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Mitsubishi Motors Corp., on the other hand, is staying a lot closer to what we drive today with its gasoline direct-injection engine. The company has sold about 400,000 vehicles with the GDI motor in Japan and Europe, says Junzo Ishino, vice president of media relations in the company’s Detroit office.

Although Mitsubishi has set no timetable for bringing the technology to the U.S. market, Ishino says the company is working on cost and emissions issues that must be solved beforehand. The big part of that puzzle is the sulhpur content of gasoline outside of California. The other 49 states allow fuel with a much higher sulphur content, which defeats some of the emission technology.

Diesel engines already employ direct fuel injection, but previous attempts to use the method with gasoline ran afoul of the fuel’s low combustibility. That 15-1 ratio of air to gasoline can’t get much leaner or richer--or the fuel won’t burn properly, soot forms and performance suffers.

Mitsubishi’s GDI engine uses a combination of electronics, airflow and fuel-injection timing to overcome combustion problems.

Specially designed injectors deliver fuel directly into the cylinder instead of an intake manifold and offer a variable spray pattern. Mitsubishi’s design places a large emphasis on the direction of airflow in the cylinder and the shape of the piston. Air is delivered through a nearly vertical intake passage and the crown of the piston has a cavity in the top. The result is that air flows in such a way as to prevent spark-plug fouling, a major stumbling block of earlier direct-injection gas engines.

When engine speed is constant, the GDI runs in an ultra-lean combustion mode in which gasoline is injected in a more concentrated pattern during the compression stroke instead of during the intake stroke. The result, Mitsubishi says, is low fuel consumption comparable to that of a diesel engine and about 30% better than that of a conventional gas engine.

Under a high load, as during acceleration, injection takes place during the intake stroke in a cone-shaped pattern. In this case, the engine operates like a conventional fuel-injected motor but develops more power in the form of increased torque, Mitsubishi says.

Another inherent advantage of direct injection is that it suppresses knocking during acceleration. Mitsubishi takes this another step by using a two-stage mixing technology to further prevent engine knock. This is achieved by injecting about one-quarter of the total fuel volume during the intake stroke and the remainder during the compression stroke. The first-stage fuel is too lean to burn and thus prevents preignition detonation. The second stage of injection is richer, and because it is formed immediately before the spark plug fires, there isn’t enough time for knocking to occur.

Mitsubishi adds a reactive manifold, exhaust-gas recirculation and new catalytic converter technology to achieve lower emissions, but again, only with low-sulphur fuel.

And what of diesel engines? Concerns about particulates and whether they are carcinogenic casts a new cloud over this venerable fuel. However, Chrysler has said it still believes that even light trucks--pickups, vans, SUVs--can be powered by the fuel.

Although these variations on the gasoline engine offer near-term promise for meeting emissions standards, industry observers see them as a bridge to something completely clean, such as fuel cells. The advantage gasoline engines have over alternatives such as compressed natural gas and propane is the existing distribution network for gasoline.

Because fuel cells will use a liquid, perhaps methanol, the places and means of fueling those vehicles will be very much like what we have today.

And that familiarity, plus “step on the gas and go” reliability, are the two things the market demands.

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E-mail questions and comments for Dr. Gear Head to highway1@latimes.com