E85 vs E10

[fivespeed3.0]

I have a 2000 3.0 Flex fuel. When I run regular gas (Shell Mid Grade E-10) and punch it a little, I get pinging. But, when I run E85 and punch it, it goes great without any pinging. Why is the higher octane preventing the pinging? Aren't these Flex Fuel engines supposed to run well on either? This has been happening since I bought it new, and Ford couldn't find anything wrong.

 

[triumphrider-1]

The higher the octane value the higher the resistance to pre-ignition.

As to the pinging with Shell mid-grade . Someone else could hopefully help you better with that.

 

[fourwheelford]

I hate shell gas, my truck runs like crap on it. Also these engines are known for pinging, high octane fuel like e85 is way higher in octane than mid grade 89 octane thus no pinging. I always run mid grade but last tank I ran 87 and it ran like crap, never again. I usually use chevron or texaco gas, I notice shakes and shudders more than anyone I know and I know its crappy shell gas that does it, my volvo, honda and this truck hate shell gas.

 

[evanesce69]

the ethanol in the e85 burns with a slower flame front, since the propogation of the flame front is slower it doesn't "explode" as noticably.

it is the quickness and intensity of the low octane fuel "explosion" that causes the spark knock that you hear with mid and low grade E10 fuels.

with that said, it is also true that octane reduces the chance of autoignition.



Both of these properties are responsible for preventing the dreaded spark knock!

 

[McCormack]

Ethanol also has a cooling effect on the intake charge, which also helps limit pinging.

 

[Froggmann]

E85 actually has a slightly faster flame/burn rate than gasoline.

 

[fourwheelford]

E85 produces less energy then gasoline when it ignites, that is why the mileage goes in the toilet it takes more to get the same affect.