I also dont no, just come to know from my mech. according to him, this 2 speed radiator fan is more cooler compare to ori one. ofcours need some mod lah..
when dis happens my rev feels like a pull back, drop of performance for 1 sec,,,, on dyno machine at each run, it always happens at dat region, thus im not able to pull above dat region, as da a/f ratio fluctuates up...