What are superchargers and turbochargers?

If the induction air entering the engine is pressurized, or boosted, by either superchargers or turbosuperchargers, the aircraft’s service ceiling can be increased. With these systems, an aircraft can fly at higher altitudes with the advantage of higher true airspeeds and the increased ability to circumnavigate adverse weather.

As a normally aspirated aircraft climbs, it eventually reaches an altitude where the engine is unable to perform a normal climb. That altitude limit is the aircraft’s service ceiling, and it is directly affected by the engine’s ability to produce power.

To increase an engine’s horsepower, manufacturers have developed forced induction systems called superchargers and turbosupercharger systems. They both compress the intake air to increase its density. The key difference lies in the power supply.

A supercharger relies on an engine-driven air pump or compressor, while a turbocharger gets its power from the exhaust stream that runs through a turbine, which in turn spins the compressor.

When it comes to normally aspirated engines, the density and pressure of the air play a crucial role in determining how far your engine will stray from its rated horsepower at sea level. In other words, the higher you fly, the thinner the air entering the intake manifold of the engine will be.

So, for a normally aspirated engine, it is not possible to have a manifold pressure higher than the existing atmospheric pressure, whereas a supercharger and a turbocharger are capable of boosting the pressure higher.


Pros – Turbochargers

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 wastegate (which is sometimes an automatic function).

Cons – Turbochargers

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 a 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.


Pros – Superchargers

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).

Cons – Superchargers

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, more parts 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.

But now, 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.