I measured a 23 deg. retard on mine (I was told it was supposed to be 24 deg but can't remember who it was I was talking to) and I have used it on my SuperTigre 51 which turns just over 15,000 on the ground. I have never heard it misfire so the limit is over 15,000. Bill or Terry at CH can probably tell us what the limit is as the RCXL is based on his design.