Flirting with Forced Induction: Turbos and Superchargers

As MPG requirements continue to climb, automakers have begun placing smaller engines into everything in their product line. V6 engines are replacing big V-8s, and cars with V-6s are down-grading to fours. Yet while cylinders are going away, they are being replaced by turbos and superchargers in order to give us all the same power with more efficiency. A smaller engine might initially seem like a sacrifice, but this is actually a huge boon for drivers, especially if you happen to live well above sea-level.

To understand how turbos and superchargers work, it helps to think of an engine as a machine that breathes. It inhales in order to create an explosion at the spark plug, and exhales to get rid of the exhaust. So just like humans, the thicker and more available the air, the better an engine can perform. Each cylinder is the epicenter for thousands of controlled explosions every minute, and providing an engine with more air allows for more fuel and each explosion can be more powerful.

Turbos and Superchargers both “supercharge” the air by compressing more into the same space. A “naturally aspirated” engine takes in only as much air as can be found at whatever elevation it operates. A supercharged engine can horde more air and force as much as possible through the system no matter what altitude or pressure its surroundings might provide.

A turbo looks and runs similar to a hair drier, sucking air into its snail-shaped turbine to pressurize it before blasting it out the front. The exhaust leaving an engine actually spins the turbo, ramping it up to optimal levels of compression by using the movement of the waste gasses. This creates the lag, or slow feeling, when a turbo car first gets moving. Once enough exhaust pressure builds to drive the turbo, the engine will kick back power far beyond its size.

Superchargers look like fan-bladed rolling pins interlocking together to shove air between them. Unlike a turbo, the supercharger is belt driven directly from the engine driveline. While this direct-drive eliminates lag, it requires more engine power just to keep the supercharger moving. For example, the supercharger system on the Corvette ZR1, requires the horsepower from a small hatchback in order to move.

Either way, turbos and superchargers allow smaller engines to put out big power. And while a naturally aspirated engine loses power as it climbs to higher elevations, cars with turbos and superchargers can compensate. For those in any mountain town this can be a godsend and buying a turbo or supercharged model means you might actually get the horsepower the carmaker claims.

Like Pepsi vs. Coke, there is an ongoing debate about whether superchargers or turbos are better for the enthusiast driver. But consider that some automakers, like Audi, use both technologies depending on the model. General Motors and Ford also use both ideas, with small cars using turbos and big bruisers getting superchargers. The answer depends on the car and your usage.

Ultimately, just know that if you want performance with your MPG, or live at high altitude, you’ll want your next car to say “Turbo” or “Supercharged” on the back. I’m not saying go buy these badges and stick them to your trunklid, either. Do yourself a favor, embrace smaller engines with a turbo or supercharger. The result will be better MPG and more high-altitude power.

Truly a win-win.