E10 91 mogas slows my -7 around 4-5 mph at cruise.
For the grins of it, I A/B compared 100LL from one tank to 91 mogas ruined with 10% ethanol from the other tank. The lower energy density of ethanol through a volumetric measuring device like a carburetor assures you can't make the same horsepower. In my case it's about 12-13 hp or so lost to the corn lobby. The numbers at 8,500 ft/21.5 in/2400 rpm/100 ROP: 100LL = 198 mph, E10 = 193-4 mph. Nothing calibrated, it's all wet-thumb-to-the-wind rigorous, but the trend is right.
When MTBE was the Greenies darling, my 172 lost ~2 mph.
What was more interesting is the time it took for the different fuel to make it from the selector to the engine: 3 1/2 minutes! I couldn't believe there was that much volume in the system to keep the mill turning at cruise power for so long. Think about that if you ever start sucking contaminated fuel. Changing tanks may not help before you run out of airspeed/altitude/ideas.
John Siebold
Boise, ID
For the grins of it, I A/B compared 100LL from one tank to 91 mogas ruined with 10% ethanol from the other tank. The lower energy density of ethanol through a volumetric measuring device like a carburetor assures you can't make the same horsepower. In my case it's about 12-13 hp or so lost to the corn lobby. The numbers at 8,500 ft/21.5 in/2400 rpm/100 ROP: 100LL = 198 mph, E10 = 193-4 mph. Nothing calibrated, it's all wet-thumb-to-the-wind rigorous, but the trend is right.
When MTBE was the Greenies darling, my 172 lost ~2 mph.
What was more interesting is the time it took for the different fuel to make it from the selector to the engine: 3 1/2 minutes! I couldn't believe there was that much volume in the system to keep the mill turning at cruise power for so long. Think about that if you ever start sucking contaminated fuel. Changing tanks may not help before you run out of airspeed/altitude/ideas.
John Siebold
Boise, ID