ORIGINAL: av8tor1977
Well, I'm thinking the sound you are hearing is probably detonation or preignition.
...
Just had another thought... Normally these small motors don't need high octane fuel, but this is a special case. I wonder if you used premium gas for your mix if this would help. Pretty easy to try...
I talked to the 'car racing guy' and what he said, the Nitro will not cause preignition. The same with methanol.
I remember, when I was using 50-50 mixture, I used 91oct gasoline, but for nitro test I used 87. So you might be right that the pinging is caused by using a gasoline with not enough octan grade. I think this will call for my next test: mixing 91 oct gas with methanol and glow fuel. I have some premix 91oct gasoline with Motul oil 1:33. I will need then less oil from the glow fuel, so I will need to use higher nitro content. I have some Norvel fuel (35% nitro) so I will mix:
0.5 oz of Norvel fuel (35% nitro)
3 oz of my 91oct gas/oil mix (1:33)
2.5 oz of pure methanol.
This will give:
45.6% Methanol
48.5% Gasoline
3% Oil
2.9% Nitro
Let's see if I still hear pinging.
RysiuM