Debra
01-04-2007, 10:07 AM
I've read your column a few times and find it interesting to read. I'm interested in moving up into gas engines and I'm curious about the octane rating of the gas for these model engines.
For a typical gas model engine: like DA, Fuji, or Zenoah, etc... what is the recommended octane rating of gas used for these engines ?
What happens if you use higher octane gas like Sunoco Ultra-94 (94 Octane) in these small engines ?
Can you damage the engine using higher octane gas ?
Do you have to change the oil mixture or high/low needle / carb adjustments if you use different octane gas ?
Thanks,
Greg
Dear Greg
There is a mistaken belief that the higher the octane rating of the fuel, the more power an engine will develop. This is definitely not the case. Higher octane fuels are less prone to detonate when higher compression ratios are used. Detonation is caused by the expanding gases compressing the fuel mixture ahead of the flame front causing a secondary explosion. The piston diameter (bore) in our model engines is too small, and the flame front too short a distance to travel, to cause this to happen. There is no need to use higher octane fuel than 87. Additives used to increase the octane rating can actually form more unwanted deposits in an engine.
Regards
Clarence Lee
(to write to Clarence, email man@airage.com)
For a typical gas model engine: like DA, Fuji, or Zenoah, etc... what is the recommended octane rating of gas used for these engines ?
What happens if you use higher octane gas like Sunoco Ultra-94 (94 Octane) in these small engines ?
Can you damage the engine using higher octane gas ?
Do you have to change the oil mixture or high/low needle / carb adjustments if you use different octane gas ?
Thanks,
Greg
Dear Greg
There is a mistaken belief that the higher the octane rating of the fuel, the more power an engine will develop. This is definitely not the case. Higher octane fuels are less prone to detonate when higher compression ratios are used. Detonation is caused by the expanding gases compressing the fuel mixture ahead of the flame front causing a secondary explosion. The piston diameter (bore) in our model engines is too small, and the flame front too short a distance to travel, to cause this to happen. There is no need to use higher octane fuel than 87. Additives used to increase the octane rating can actually form more unwanted deposits in an engine.
Regards
Clarence Lee
(to write to Clarence, email man@airage.com)