If you have a turbocharger or supercharger in your plane, it means you're able to blast off to cruise altitudes that normally aspirated engines could only dream of. But what's the difference between a turbocharger and a supercharger? And when is each one used? Let's take a look.

How A Turbocharger Works

First off, how does a turbo work? Well, it uses exhaust gas to turn a turbine, which compresses and forces more air into your engine. And when you have more air entering your engine, you can add more gas for your engine's fuel/air mixture, which means you'll get more power. Turbos are especially useful at high altitude, where there is considerably less air than at sea level.

The diagram below does a pretty good job summing it up how a turbo works.

How A Supercharger Works

Next up, the supercharger. In theory, it's almost exactly the same as a turbocharger, except for one main difference: it's driven by the engine's crankshaft, and it's usually connected with a belt or chain. That's important because a supercharger requires engine power to run, as opposed to a turbocharger, which runs off of waste exhaust gasses.

The Turbocharger: Pros And Cons

Like anything, there are pros and cons to a turbocharger.

First, the pros.
Turbochargers are more efficient than superchargers, because turbos use waste air that's already exiting through the exhaust pipe. Though they don't run completely "free of charge". It does take energy for the engine exhaust to turn the turbine.

But in comparison to a supercharger, turbos use less fuel, and they typically have less total weight than a supercharger. Finally, most turbochargers provide a better total increase in horsepower than superchargers, because their speed can be changed by adjusting the waste gate (which is sometimes an automatic function).

Now for the cons.
Most turbochargers suffer from lag. Because it takes a second or two for exhaust gas to spin up the turbine, there is a delay from when you throttle up your engine, to the time the turbine achieves its desired speed and output. Next, turbos provide little to no benefit at idle and low power settings. And finally, turbos can suffer from power surge. This happens when you rapidly reduce power, and air pressure quickly builds in the intake manifold, causing a temporary flow reversal and vibration. Surge isn't as much of a problem with modern turbos as it used to be, but it's something that you need to watch out for, especially if you're flying older turbocharged aircraft.

The Supercharger: Pros And Cons

Obviously, there are pros and cons to a supercharger as well.

First, the pros.
Superchargers have no lag, they boost an engine at low RPM, they run at cooler temperatures than turbos, and they're relatively cheap in comparison to turbos (those turbines can get really expensive).

Now for the cons.
Superchargers are inefficient, because they require quite a bit of engine power to turn. That makes superchargers less fuel efficient than turbos. And finally, because they use a system of pulleys and gears to turn, there are more parts that can break.

Superchargers Started It, But Turbos Are Here To Stay

Back in the mid-1900s, and especially during WWII, superchargers were usually the engine boost of choice. Their simpler operation was one of the main reasons. Another reason they were popular was a lack of metals that could handle the heat produced by turbos. Gas was also very cheap, so it wasn't that big of a deal to burn a little more gas to get the power output you wanted.

High temperature alloys, lighter weights, and better fuel efficiency have all made turbos the best choice for almost all of today's aircraft. And, with automatic waste gates on many models, they're easier (and more foolproof) to operate than ever before.