Asking the question another way-
I have just recently gone to a 9:1 compression on my IO-360, ported cylinders - Impulse Bendix left, LSE plasma II right. CHT's and oil temps ran high at 25 BTDC and LSE at 0 TDC (static). Reset mag to 20 BTDC and LSE to 5 degrees after TDC static (as recommended by Klaus for the LSE with 9:1 compression).
A really good idea, but the EI is still advanced of a normal magneto
This dropped temps down to normal -CHT's high 390's, WOT, 2600 RPM in a climb and 185 max oil, leaned to 150 ROP.
High 390's is not what I would call normal but I bet it is much better. If you are leaned to 150ROP in the climb were you at 7000'/2600RPM at the time? If not you were not rich enough and that is not helping your CHT's. And how did you know it was 150dF ROP, did you find peak and come back again or was it a guess? In flight, engine runs well with fuel flows and performance as expected at appropriate ROP cruise settings (150 - 100 ROP depending on percent power)
Hopefully 65-70/75%. When securing the mag in flight at these higher power settings, the engine continues to run fine (no speed decrease) but my CHT's will still drop 20 degrees or so.
That is normal of any engine, as the ThetaPP has increased as a result of only one plug firing.
That indicates to me that the mag is still more advanced than the LSE at that power setting.
I think that is a wrong assumption Seems I could advance the LSE a few degrees to basically match the advance of the mag (as opposed to further retarding the mag to match the LSE - this would result in "less advance" than optimal).
I think you have this around the wrong way. You would need to retard the EI to match the mag if you wanted to do that.
So I guess my question is, With no engine dyno in flight, how do you know if you have optimized your timing to somewhere near the spot Michael describes??
Ahhh Optimised ThetaPP, well you can do it if you have an ignition system that reads the peak pressure and crank angle continuously and makes individual spark plug firing changes to achieve the optimal output. And no this is not available in your cars either. There is such a system that is patented and still under development. I could mention the companies name but some folk here get all excited with me promoting some folk from Ada Ok. You could just click here http://www.gami.com/prism/prism.php
Seems to me you want as much advance as possible while getting acceptable CHT's (380 or so max for me in ROP cruise) assuming all other parameters are in agreement with the charts.
CHT is not a good parameter to use as a target, and you do benefit from some advance, but not as much as many think. But when LOP it certainly helps.
Sounds obvious but it takes some fiddleing. I guess this is where the ability to read advance in flight (via the P-mag Commander or similar) becomes valuable.
Helps you in some sense but reading the ICP and ThetaPP is where you really want to be. ?.not so easy for most of us.