Auto Advances: Turbocharged Renaissance

By John Voelcker|Wednesday, September 26, 2012

1. Air gets drawn in from the atmosphere

2. Exhaust from engine spins turbine

3. Spinning turbine drives the 
air compressor

4. Compressed air 
forced into engine

Electric cars get lots of attention these days, but your next vehicle’s higher gas mileage may well come from more familiar technology: turbocharging. Oldsmobile launched the first turbo for passenger cars 50 years ago, but they are now moving rapidly into the mainstream, allowing for smaller engines that generate as much power as their predecessors while using less fuel.

Engines produce power when a spark causes gasoline vapor and air in the cylinder to explode. A turbo uses the rush of exhaust gases exiting the engine to spin a turbine, which drives a compressor that crams extra air into the cylinder. More fuel burns, thus generating more power.

For decades, though, turbochargers had a problem: Engines running at low speeds did not release sufficient exhaust to power the turbo. When the driver accelerated, the turbo needed time to build up enough oomph to force air into the cylinder, resulting in a sudden surge of acceleration from the engine a second or two later. To combat this obstacle, carmakers have designed smaller, lighter turbos that respond more quickly. They have also fitted engines with electronics that maximize power and smoothness by timing the spark based on speed and gas-to-air ratio, and added direct injection of gas into the cylinder.

These advances yield big dividends. The turbocharged 1.4-liter engine of the 2012 Chevrolet Cruze generates nearly as much horsepower as the 2.2-liter in the 2010 Chevy Cobalt, and it gets three to four more miles per gallon. Turbo maker Honeywell estimates 70 percent of light vehicles will have turbos by 2020.

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