Ethanol & engine timing

[Howard M.]

Just curious, does the use of current unleaded gas with 10+ % of ethanol change the engine timing set points in any way?
Thanks

[Bill I.]

Re: Ethanol & engine timing

Howard, with 10%, as we have here in Fl., I should think not. At least, not for my 67. Bill.

[Duke W.]

Re: Ethanol & engine timing

No, the flame propagation speed (as long as detonation is not present) for virtually all gasoline blends is about the same. It would take very sensitive test equipment to see a difference.

As a rule of thumb, retarding or advancing the spark advance from the optimum for peak torque (in the absense of detonation) at any given engine load/speed condition drops the value by about 1 percent.

The maximum allowable proportion of ethanol by volume under current EPA regulations is ten percent . There is no such thing as 10+% ethanol. That would be a violation of current regulations, which could result in substantial fines for the fuel blender.

Duke