E-85 mods

[8cylRWD]

Can anyone tell me all of the exact differences between a standard fueled truck and a "Flex Fuel" truck?? (I tried to post this in the "ask the Ford mechanic section but the site won't let me post anything there.) Thanks

 

[stmitch]

On flex fuel 3.0's, there are several differences within the fuel system. There's an ethanol sensor, and corrosion resistant materials are used throughout the fuel system. Flex fuel 3.0's also have slightly different heads with smaller combustion chambers than standard gas 3.0's. Flex fuel also requires larger injectors than standard gasoline (typically around 20% larger). Most importantly, there are also major differences in the ECU programming.

 

[8cylRWD]

Thanks. Have been playing around with 30%-40% blends in my '94 4.0. I am aware of the corrosive nature of ethanol since I used to haul it. With E85 (E75 this time of year) priced 30-40 cents under E10 it is pretty much a trade-off of cost savings vs mpg loss. Really start to notice the need for bigger injectors when driving into a strong headwind on the highway with th 40% blend. Around town, the power loss is noticable if you are really paying attention.
You mentioned smaller combustion chamber on Flex Fuel engines. Does that translate to higher compression ratio on the Flex Fuel vehicle to take advantage of the E85's higher octane?

 

[stmitch]

Yes. On the flex fuel 3.0's the smaller combustion chamber does result in a slightly higher compression ratio. It's not a major difference in size, or compression ratio though. I notice my flex fuel truck runs much smoother on e-85, and actaully has a little more power too.
If you wanted true e-85 abilities, you could get larger injectors, and have tunes written to accomodate the new fuel type. You wouldn't be able to do true flex fuel tunes though, so you'd have to run the tank almost empty, and then change back to a gasoline tune if you wanted to switch fuels.