- The Washington Times - Friday, August 28, 2009

By the time the Steam Age was losing steam, engines used in locomotives had become incredibly complex and efficient. The basic concept of a heat source — a boiler and a cylinder with a sliding piston — still lay at the core of the last steam engines, but they were supplemented with all manner of “triple-expansion” and “compound” systems to help them wring every possible watt (a unit of energy named after James Watt, who contributed to the development of the steam engine).

Today it is the gasoline engine that is losing gas. Well, not exactly losing gas. The gasoline engine is enjoying incredible technical advances that will prolong its useful life as the primary power plant for passenger transportation.

The growing emergence of hybrid and battery electric cars not only puts more pressure on gas-powered cars to be more efficient, but the high cost of hybrids and electric cars provides an opportunity for auto manufacturers to introduce new technology to gas engines that is cheaper than a hybrid drivetrain.

Direct injection is an example of a new add-on technology that makes an engine squeeze every last bit of energy from gasoline fuel, improving fuel mileage by about 3 percent, according to General Motors. The design is familiar enough because it works just like the fuel injection system of a diesel engine.

Direct injectors blast gas into the engine’s combustion chamber at sufficiently high pressure for it to atomize into the fine mist necessary for combustion without the head-start given when gas is injected into the intake manifold or intake port. In those traditional systems, the gas has more time to evaporate before electricity sizzles across the spark plug gap to ignite the air/fuel mixture.

The benefit of shooting the gas straight into the combustion chamber is twofold. First, it gives the engineer absolute control over every molecule of hydrocarbon, with none of it boiling off as evaporative toxic emissions pollution. Second, because all of the evaporation occurs inside the combustion chamber, the evaporation process pulls heat out of the engine as it vaporizes the fuel.

This reduced combustion chamber temperature permits a higher compression ratio, letting the engine make more power with the same amount of fuel. This is particularly beneficial in the case of turbocharged engines, which normally must run a low compression ratio to offset the extra pressure from the turbo.

But with direct injection, turbo engines can have high compression ratios for maximum power and efficiency. This is the foundation of Ford’s EcoBoost engine strategy, which aims to replace V-8 engines with similarly powerful turbocharged, direct-injected V-6s, and to replace popular V-6s with thriftier, but equally powerful, four-cylinder engines. The company has seen strong demand from consumers for its Ford Taurus SHO, Flex and Lincoln MKS models equipped with the direct-injected EcoBoost engine.

General Motors has rolled out its four-cylinder direct-injected engines with an EPA highway fuel economy rating of 32 miles per gallon for the 2010 Chevrolet Equinox. The direct-injected version of the 2.4-liter Ecotec engine boasts 9 horsepower more than the port-injected version of the engine while improving on its economy.

General Motors changed more than the fuel injection system on its engine though, because like diesel engines, they can be noisy. To minimize the noise and better withstand the stresses that cause noise, GM’s engineers switched to a higher-grade aluminum and reinforced the design of the engine block to make it stronger, said Amy Joss, assistant chief engineer for Ecotec engines.

For the Taurus SHO, Ford also sought to suppress the diesellike growl of that car’s direct-injected EcoBoost engine with good old-fashioned sound insulation around the engine, including a bottom tray that seals the sound in the engine compartment. This approach works very well, as the Taurus never betrays the use of noisy fuel injectors.

With direct injection in place and powerful engine management computers aboard, cars are poised for what could be the last step in the evolution of the gasoline engine: Homogeneous Charge Compression Ignition, or HCCI.

General Motors is working hard on HCCI technology, which adds the final aspect of diesellike characteristics to gasoline engines: ignition by high compression rather than with a spark plug. The HCCI engines will switch between conventional ignition and compression ignition as conditions permit for maximum fuel economy.

Manufacturer photos: Engines are running cleaner and faster with Direct Injection, such as with Ford’s new EcoBoost V-6 in the 2010 Flex and in GM’s new 2010 Chevy Equinox



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