Engine In How turbos and superchargers work

To get both fuel economy and horsepower, automakers are increasingly turning to forced induction.

"Jeff Allen, Brian Blades, Chris Cantle, Jay McNally, Bert Swift & Marc Urbano"

Big engines provide a satisfying surge, but most of the time we're using only a fraction of an engine's maximum power. To increase fuel economy, automakers are rapidly employing smaller engines—both in displacement and cylinder count. Downsized engines can, however, produce big-motor power with the help of pumps that force more air into the engine. The extra air, combined with fuel, makes a more powerful "boom" when the spark plugs fire, increasing horsepower.

Automotive engine pumps come in two flavors: turbochargers and superchargers. Turbos are currently the de facto small-engine power booster because they efficiently run off the engine's exhaust. This energy may be "free," but there's a slight delay between the time the driver presses the gas and when the turbo generates boost (the delay is known as turbo lag). While turbo-makers have reduced the lag with twin-scroll ducts that increase gas velocity, surviving in the over 2000 F exhaust requires exotic and expensive materials like cast stainless steel and Inconel, a nickel—chromium alloy.

Superchargers have typically been employed when peak power—not saving fuel—is the ultimate goal (see the Corvette ZR1). But refinements like helical rotors and a bypass system for coasting have increased the blower's efficiency so that several automakers are keen to take advantage of the supercharger's relative simplicity and lower cost. Plus, a supercharger offers near instantaneous response, so a downsized, supercharged engine feels punchier in heavier vehicles like SUVs. Compared with a nonboosted engine of equal power, a smaller "pumped" one is roughly 10 percent thriftier, which is why the majority of new-car engines will almost certainly be boosted by the end of the decade.

This article originally appeared in .



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