Getting Small, But Avoiding Econoboxes

Published May 6, 2008

General Motors is expected to replace the 1.6-liter engine in the Saturn Astra—with the turbocharged 1.4-liter engine.

Conventional wisdom for American automobiles is being turned on its head by the combination of high fuel prices, concern about greenhouse gas emissions, and a looming recession. The auto industry is responding by taking a page out of Europe’s playbook—where smaller cars and smaller engines rule, but driving fun has not been banished from the equation. Smaller yet powerful engines are possible due to advances in supercharging, turbocharging, and direct injection.

Supercharging and turbocharging are related technologies—both are concerned with compressing more air into the combustion chamber of the engine. This increases the power when air and fuel combine with a spark, but also increases efficiency of the combustion process. What’s the difference between the two? Supercharging uses a belt to compress the air while a turbocharger uses exhaust gases from the engine to power the compression.

Supercharging has been around for decades. A decade ago, Buick offered supercharged models to deliver V-8 like performance in its V-6-powered flagship models. Supercharging in the current Jaguar XF V-8 boosts the car’s performance to the level of a V-10 or V12 engines, while maintaining a modicum of fuel economy. European automakers are now looking at adding giving the supercharging treatment to small displacement engines in the 1.2 to 1.5-liter range.

Turbocharging is finding a much broader application as durability concerns have been addressed and new variable-vane turbochargers deliver smoother power for the driver—ending the complaints of the past about “turbo lag”. Volkswagen and Renault are leading the way, but Ford, General Motors and Fiat are not far behind.

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VW is introducing a 2.0-liter turbo four that puts out power comparable to that of a V-6. Renault has a 1.3 and 1.4 turbo engines that will replace its 2.0-liter, providing the same amount of power but increasing fuel economy. GM has a turbocharged 1.4-liter engine coming up in the Astra—just introduced as a Saturn in the U.S.—that is designed to replace its 1.6-liter engines. Ford’s EcoBoost engine strategy in the U.S. will introduce a European 1.6-liter turbocharged engine to replace its 2.0 and 2.3-liter engines in the Focus.

In Europe, gasoline engines are also combining direct injection with turbocharging, as has been done for years with diesel engines. Direct injection pressurizes the fuel before delivering it into the combustion chamber, increasing power and efficiency.

Direct-injected turbocharged small engines—that will appear in compacts like the Honda Civic, the Chevy Cobalt and Saturn Astra—are expected to debut in Europe and then migrate to the United States. These engines promise less weight, higher horsepower, and better fuel economy. Audi already introduced a Special Edition A4 this year with a direct injection, 2.0-liter turbocharged four-cylinder engine that produces an incredible 200 horsepower while delivering combined fuel economy of 23 miles to the gallon.

These fuel economy gains may seem modest compared to hybrids, but the industry is looking for most cost-effective ways to offer efficiency while delivering sufficient power. Engine downsizing, combined with turbo- and super-charging is one strategy to achieve that goal.