Offshoreonly.com - A/F ratio and 10% Ethanol

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A/F ratio and 10% Ethanol

Thought I'd throw this out there to generate some discussion. Seems now that everyone is being forced to run e10, there are some tuning factors to consider. Everyone knows that it takes more fuel to generate the same amount of power with e10. What we're seeing is a need to run the A/F about .4-.5 richer than with pure gasoline to get peak power on the dyno. I can see this being an additional evil of e10(or e15), especially if you've got a high performance engine running on the edge. Curios to hear other's thoughts and experiences.

Bob Lloyd
Full Throttle Marine

Quote:

Originally Posted by bobl (Post 3336935)

VERY good point, I thought about this while doing the rebuild with the Procharger and was worried about what octane to use and then the ethanol issue comes up.....thing that worries me is knowing what the ethanol % is, are they required to tell you there is ethanol? and if so, are they required to tell you how much etc...???

If you're going to monitor A/F ratio, which would be the best option, simply find a gauge that will display Lambda instead of air/fuel ratio.

Air/fuel ratio is always dependant on a known stoichiometric value for the fuel being burned. Because we don't always know this value, Lambda is a better way to measure.

Lambda = 1.00 at the stoichiometric point for any fuel. The wideband O2 sensors on the market today are actually Lambda sensors, and the box or gauge they connect to are programmed for the stoich point. If you have a gauge for gasoline, it's probably programmed for a 14.64-14.7:1 stoich point. When you run E10, the difference in stoich point now makes the gauge read wrong.

If you were looking at Lambda, the Lambda stoich point is always the same, as is the burn. For instance, if gasoline has a stoich point of 14.7, and you want your engine tuned for 13.0:1, then you're really tuning to Lambda = 0.88 (13.0 / 14.7). Because the Lambda value is constant and not calculated based off a set stoich point, if you watch your gauge for 0.88 all the time, you know if it's running lean or rich compared to your target.