For those who are just getting into modifying their vehicles, the prospect of a turbocharger sounds great. Adding a part to increase the power of the engine seems like a win-win situation. However, there's a reason that turbochargers are not standard equipment on just about every vehicle, as there are some significant drawbacks that come with installing one.
The idea behind a turbocharger is simple. Cars need fuel and air to function, but they are limited by the amount of space in the cylinders. More cylinders means more space for fuel and air, which is why a V8 engine typically outperforms a V6 - it simply has more room to fit fuel and air, resulting in more power. Yet adding cylinders also adds weight, which decreases fuel economy and causes other issues. Thus, the turbocharger was born as a way to get more power without adding more cylinders.
The turbocharger compresses the air that goes into the engine, allowing the cylinder to fit more. This results in more power, and the engine can handle more fuel and air than it typically could without a turbocharger. However, this results in a couple of issues.
"Knocking" refers to when the air and fuel mixture in an engine combusts before it's supposed to, and this is a significant problem with turbocharged engines. Compressed air has has a higher temperature, meaning that it can actually ignite the fuel before the spark plug fires. Not only does this hurt performance, but it can damage the engine itself. This is especially true in engines not built for turbochargers, so drivers using them as aftermarket parts need to be careful. Using a higher octane fuel is one way to avoid this issue, but that's a hidden cost that many turbocharge purchasers do not take into account.
Another issue that drivers may have heard of is "turbo lag." By adding an extra step to the engine process - compressing the air - the engine is simply not as responsive with a turbocharged engine. It takes longer for the air to get to the engine, so drivers may push the gas and not feel the jolt until a few seconds later. Some automakers pay close attention and do everything possible to reduce turbo lag, but it's almost impossible to eliminate completely. Thus, automakers that want a smoother ride tend to avoid turbochargers.