Post Master General
Join Date: Apr 2012
Location: Bowling Green, VA
I Ride: '09 ZX6R
The OEM R/R, at least through '18, is a shunt design. That means when the battery is fully charged (indicated by~ 14.3 VDC at the battery terminals) all excess power is dumped into a load resistor. The alternator runs at maximum when this happens, and keeps doing so for as long as the bike is running.
The regulator portion is a sense circuit that controls a relay to switch where the current flows. Simple on / off setup.
FET R/R use a different approach to limiting excess power being applied to the battery. The regulator portion uses a field effect transistor (FET) to act as a valve on the current flowing out to the battery. Instead of just switching tracks and letting the alternator run at WFO, the FET changes the resistance going to the battery so less current flows. Closes the tap, so to speak. The alternator output goes down, and less heat is generated.
If you want to replace the OEM R/R, I'd go aftermarket FET.
This all matters on a race bike, because the electrical load is considerably less than a street bike. Takes much less time to recharge the battery, if you're not running any head lights, market lights, etc.
"Basic stuff fellas. Use your head for something other than to break your next fall." Words to live by