07-09-2013, 01:31 PM
Hey guys, here are my thoughts about the "octane discussion" in our case, the CB. Octane does not dictate the flame propagation speed all that much, but the resistance of the fuel to vaporize and mix with air, becoming a burnable substance. Higher octane fuels have more resistance to mix into air and therefore burn. Using significantly more octane than an engine is calibrated to utilize, like 110LL in your mower will make it a little more difficult to start on really, really, cold days. It will also make less torque, fuel makes torque, RPM makes horsepower. Also timing makes torque....and so on. The perfect amount of ignition lead is when the fuel/ air mix burns with flame propagation that is even and controlled and peak pressure happens just after TDC. Too little octane (or too much ignition lead) causes knock, the fuel/air mix to burn to early and peak cylinder pressure happens before TDC. This causes the cylinder to ring at a frequency that is directly proportional to the bore size due to the rapid rise and fall in cylinder pressure.
So to sum it up, the V.E. tables and ignition lead on the CB are are conservative enough for E10 gas....it just doesn't matter. Just my two cents. Mine does get premium if the wife and I fill up on the same pump. She has a higher compression engine that requires it.
So to sum it up, the V.E. tables and ignition lead on the CB are are conservative enough for E10 gas....it just doesn't matter. Just my two cents. Mine does get premium if the wife and I fill up on the same pump. She has a higher compression engine that requires it.