Why Does Ethanol Make So Much Power? (Versus Gasoline)

Summary by Krater

An explanation of why ethanol produces more engine power than gasoline despite having lower energy density, covering air-fuel ratios, octane number, and latent heat of vaporization.

From the video

Answers: Why does ethanol make more power than gasoline despite having lower energy density?

• air-fuel ratio
• energy density of fuels
• research octane number
• latent heat of vaporization
• engine knock
• brake mean effective pressure

What it concludes

• Ethanol has about 67% of the energy density by volume compared to gasoline.
• Ethanol has a lower stoichiometric air-fuel ratio of 9:1 compared to gasoline's 14.7:1.
• Adding ethanol to gasoline increases the research octane number up to about 30 to 40 percent, after which there is little chemical benefit.
• Ethanol has a much higher heat of vaporization than gasoline, providing a significantly greater temperature drop in the cylinder.
• Higher ethanol blends like E85 allow for increased compression ratios, advanced ignition timing, and higher boost, resulting in significantly more power.
• Testing shows E20 can improve fuel economy by 1 to 34 percent due to higher permissible compression ratios despite having lower energy density than pure gasoline.