(MCT) -- QUESTION: I've noticed a lot of new cars are now "turbocharged", Can you explain how this works and if it's a good idea to buy one?
ANSWER: You're correct that turbochargers are becoming very popular, to improve fuel economy and increase performance. Once found mostly on performance vehicles and diesel trucks, and some four cylinder engines in the 1980-90s, they're now mounted in about 1 in 5 vehicles in the United States. I should add that turbos have been very popular in Europe, mostly on diesel engines, for a long time.
Turbochargers boost engine power by around 25 percent on a gasoline engine and about 40 percent on a diesel, allowing a smaller, more efficient engine to be used in place of a larger one. Instead of power being largely developed only at high engine speeds, a turbo flattens the torque curve, improving driveability and allowing more efficient low-speed engine operation. Tiny three cylinder turbocharged engines are helping cars reach more than 40 mpg and performance oriented turbos allow four- and six-cylinder engines to develop as much as 400 horsepower.
Turbochargers pump air into an engine at a higher rate than would occur if the engine were naturally aspirated. Driven by exhaust gases, a turbine wheel rotates at as much as 200,000 rpm. At the opposite end of a connecting shaft, a compressor wheel draws in air and pumps it to the engine's intake manifold. A computer-managed wastegate controls boost pressure to safe levels, maximizing performance while preventing engine damaging detonation (an explosion, rather than a burn of combustion gases). An attractive feature of turbochargers is that they use wasted energy, rather than consuming it like a belt-driven supercharger.