What is the main purpose of a magneto in a high compression engine?

The primary function of a magneto in a high compression engine is to provide electrical current to the spark plugs, which is essential for igniting the air-fuel mixture in the engine's cylinders. Magnetos operate independently of the vehicle's electrical system, generating their own electrical current through electromagnetic induction. This electrical current is crucial for producing the spark required for combustion, particularly in high compression engines where the pressure in the cylinders is significantly higher, necessitating a stronger and reliable spark for ignition.

Other options, while related to engine operation, do not accurately describe the specific purpose of a magneto. For example, maintaining a battery charge is typically handled by the alternator or generator system in the vehicle, while improving fuel efficiency involves many factors including combustion quality and engine tuning rather than the role of igniting the fuel-air mixture directly. Storing energy for ignition is not the function of a magneto; instead, it produces current at the moment it is needed without storing it, making it an effective ignition source during engine operation.