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Minimum Ethanol Content for E85 Ignition Advance

Ethanol & Flex Fuel Tuning

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Hi, I have a quick question regarding minimum ethanol content. I hope the question makes sense.

I note in this video, it suggests that anything greater than 80% Ethanol Content, the ECU referenced the second ignition table completely. I take from this, that, anything above 80% content, it is safe to reference the ignition advance that was tuned with E85.

In your experience, is 80% the minimum ethanol content at which ethanol provides no greater knock resistance?

I have been informed previously that as long as we have 70% ethanol, we are safe to command the full E85 MBT timing and boost in the tune. Ie - There is no advantage (performance or safety wise) between 70% and 85% ethanol content.



*Edited for spelling

I used the mix of race gas and 96.6 percent ethanol to make it E66 and adding more ethanol did not allow me to increase ignition timing anymore at 3.2 bar of boost. But octane rating of that race gas was 130+...

Boosted or NA? NA around 70% is the starting point, depending on the CR of the engine. Boosted is around 80%, again depending on the final CR of the engine.

Thanks for the responses guys.

For reference, turbo charged LS. compression ratio 10.1

At this stage, I have not used anything but pump United E85 here in South Australia. The vehicle is flex tuned, but I do not plan on running anything but E85 unless I have no choice on a longer drive.

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