Ethanol Content
The percentage of ethanol in the fuel blend. E0 = pure gasoline, E85 = 85% ethanol. Ethanol has higher octane and burns cooler but requires ~30% more fuel volume.
Why it matters
The scoring engine adjusts lambda and fueling thresholds based on ethanol content. A car tuned for E50 running E20 will go lean because the fuel needs less enrichment than the tune expects.
What to look for
If ethanol content drops below what the tune expects, lambda will read leaner than target. Consistent ethanol content across a session means the fuel is stable.
Related terms
Another way to measure air-fuel ratio, expressed as a ratio where 1.0 = perfect stoichiometric combustion. Below 1.0 = rich. Above 1.0 = lean.
The ratio of air to fuel in the combustion chamber. Lower number = richer (more fuel). Higher number = leaner (less fuel).
Pressurizes fuel to ~2,900+ PSI for direct injection. When it can't keep up with demand, fuel pressure drops and the engine runs lean.
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