I realise this is a Dynon thread, not an engine management thread, but this is good education for anyone reading. I will try to cover these matters one at a time so hang in there.
Are you running an EI? and if so how well timed is it? Just a guess but the spark timing seems to be too advanced.
David - way off topic but interested in your thoughts. FYI WOT will bring the spark advance back to 25 BTDC on any EI so it's working like a MAG would. Other than the CHT anomaly on the display it looks like a typical climb out in hot weather from a high elevation. I agree that high CHT and low EGT are a sign of detonation but with a MAP of 19 (52% power) it's probably a unlikely possibility. Yes No? :-?
WOT does bring the EI back to its "Base setting" and this is not always 25DBTDC, and is often 26 or even more as has been reported elsewhere. There is something else to consider. And this is important;
a. In a magneto there is lag between the static timing (say 25 degrees) and the actual plug firing (dynamic) and on a typical IO360 this is a couple of degrees. On some engines it is much more (think Chieftains). This all adds up to several degrees earlier sparks than the maker intended.
b. More advance does not give more power, in fact the curve is pretty flat and then it starts losing power. The Dyno does not make this up!
A bit of advance is useful at low powers and with lean mixtures but we are not talking about much, and far less than the EI's deliver. It is true you can run to almost zero fuel type lean with an EI and the mag won't do it, but in a realistic sense who flies like that and there are other ways to achieve the same result. But thats another topic for another day.
I agree that high CHT and low EGT are a sign of detonation but with a MAP of 19 (52% power) it's probably a unlikely possibility. Yes No?
No. Common misconception. Lets get detonation out of the way first. On a conforming N/A engine with conforming fuel there will never be any at any mixture even at high powers or full rated. You should see what we have to do to get it
That being said timing set outside the spec, (which the EI always is even if only just a tiny bit) and running say mogas, on a hot day, hot oil, and CHT's above 420, now we have a recipe for starting some. But it is not likely and on these engines very hard to do, but it is possible if you get all the ingredients right.
by the way detonation only occurs between about 35dF-75dF ROP. If you go richer, or leaner, it goes away really fast. Popular myth is you will get it LOP, it has been proven to be not true. But the myths take some killing off.
As for the CHT climbing and EGT dropping, that is not from detonation. Detonation has symptoms of EGT staying around the normal and CHT climbing quickly.
Preignition events however have a noticeable sudden drop in EGT and a rapid rise in CHT. These are very destructive.
What I observe here is a stable set of data and the EGT is stable but low, and the CHT stable but high, thus advanced timing. Even if the CHT was 370dF at that EGT value I till suspect the timing is too far advanced, unless the probe placement is such that those numbers are normal for that installation.
What would be interesting if you have the programmable flexibility with your EMAGs is to set the base timing at 23DBTDC and the maximum at say 28, so that the EMAG reflects more of the design sparks at higher powers and not as much advance at lower powers and see what you get, in terms of CHT in climb and cruise, IAS at the same LOP fuel flows. If you have nothing better to do that is.
Hope this has helped a bit.
