Here's a breakdown:
* Single Turbo: Most common setup for smaller engines and less demanding applications.
* Twin Turbo: Used in larger engines to provide more power and torque at lower RPMs. This can be either "sequential" or "parallel" turbos.
* Triple Turbo: Very rare, used in very large engines for maximum power and torque, often in heavy-duty applications like mining trucks.
The number of turbos depends on the specific engine, its size, and the needs of the application.
