The other day I hooked up my OTC to look at what my advance reading was at WOT/15 PSI BOOST. The reading was zero degrees at 5000 rpm. To me this says it's firing at TDC under those conditions.
My advance from rpm2 at 5000 rpm is +11.5 and the calculated table for rpm/boost is +20 degrees at 5000 rpm. Advance from map warm full is -7.5 degrees. I dont see how any combination of those three numbers results in 0 degrees advance.
Does the OTC show true advance? It's certainly reporting everything else correctly.
I read on a turbo site that 15 degrees advance is what you want...what is the truth. I hope someone knows the answer.