Originally Posted by
1QwkSport2.5r
To me, 200rpm (only roughly 2% gain) isn't significant enough to be worth the extra $3 per gallon... Then again most of the engines I own are designed for low/no nitro anyway - some tolerate 10%, but those engines run a fine line between running good and preignition. Not to mention the 5-15% higher fuel consumption for 2-5% gain in power doesn't strike me as all that beneficial... But that isn't to say this would be the case with every engine. I tried 15% nitro in a Enya 15-IV from 80/20 FAI break-in fuel and got almost 1,000rpm gain from it. That is something to shake a stick at, but 200rpm isn't in my mind.
200 RPM is much more than 2%. Take a look at the formula for propeller torque and speed. To raise the RPM by 200 RPM the torque must increase exponentially so a 2% increase in speed is more like an 8% increase in torque, and HP may be more like 10%.