altenator pulley ratio to crank

[Dragsinger]

A general guide line for full alternator output is to overdrive the alternator 30% - 50%

Example; a 5" crank pulley combined with a 3" alternator pulley = 40% overdrive. In this example, 1500 engine RPM will equal about 2100 alternator RPM

If the alternator is of the proper amperage output for your load the above example would have full battery voltage to everything with an engine speed of 1600 - 1800 RPM

This type setup will allow you to race all day without battery charging.