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Edit: What I mean, is that typical flexfuel engine is efficient when used petrol fuel and quite ok with ethanol. A pure ethanol flexfuel engine would be an engine, that is efficient with ethanol but petrol option could be some kind of "limb mode", that engine is able to run with it, but very ruined ignition timing and with very high f/a to avoid pinging. Do anybody get, what I'm thinking?
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On my setup I have done the testing with E 100 Ethanol, E98 Ethanol, E85 Ethanol and GEM 38, GEM 40 and now testing GEM 47.
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Low static compression ratios can be worked around by running Miller cycle (effectively Atkinson cycle + forced induction).
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as Ecky posted above on my setup this is pretty much my engine type.
When I tested E100 Ethanol and petrol at light load Freeway testing, petrol always was a major winner when it came to FE. Now when it came to mid load the gains we're with Ethanol due to its knock resistance, but the Freeway amount of driving time was around 95% compared to the mid load needed.
So, it really comes down to you are trying to overcome Ethanol's numerically lowering heat value compared to Petrol. You can build an engine with high compression dynamic or static but in the end the heating values do matter.
These are just my opinion's so if you really want to build a engine that is for FE on Ethanol please do. Thinking out side of the box is always a great thing
https://afdc.energy.gov/files/u/publ...ison_chart.pdf