If you have the guy in Missouri do your computer, he can "weed out" the flex fuel scripts of the software. I think that means he essentially neuters the computer so any flex data that should be there is ignored.
If you do want to retain the ability to run more than E15, then the computer needs a way of knowing what blend of fuel is being burned. If you have 1/2 a tank of E15 and fill up with E85, the engine needs to know you have something between the two fuels and adjust the injector duration to allow proper fuel/air ratio and adjust ignition timing. This is necessary due to energy density of the fuels. E85 requires a higher volume of fuel for the same power. Now there are some benefits to E85. You can advance the timing and get more power from the engine since alcohol is less susceptible to preignition than gas. This is the reason “top fuel” drag cars run alcohol. Less energy density, but higher total energy production capability.
Easiest route is to have a custom tune done on the computer. The tuners will replace your factory flex tune with a factory non-flex tune then modify that tune to fit your use case. Some will just modify the flex tune in the computer to delete the flex parameters. With the modern software for engine tuning they have a feature called “segment swap”. This allows you to pull out a portion of the computer program and swap in a portion from a different program. Makes getting your baseline setup fast. HP Tuners and efiLive both support this.
I have a computer from a 6.0 / NV4500 truck, and a second computer from a 5.3 flex / 4l60e suburban. I plan to segment swap the trans from the truck to the suburban computer. I also plan to keep the E85 capability if I can. My plan is to buy efiLive so I can play with my computer tune and swap the computer vin for my jeep’s VIN. HP Tuner will not allow a VIN swap unless the new VIN matches what the engine could have been in from the factory (sort of).
This is what the composition sensor looks like:
I bought this one several years ago when I was planning a 258/4.0 stroker running a mega squirt computer. I abandoned that plan and my donor vehicle had one, so I currently have 2. If you want this one shoot me a PM with your address and I’ll ship it to you.
Well ive lurked here long enough... Learned and watched numerous rebuilds and time to get moving on mine.
I had a 81 Scrambler 25 years ago and put a chevy 350 and auto trans in it and loved it. Then the kids came and the jeep went. Now the kids are gone and i found another 81 that Started out as a old Jeep Tour Company Scrambler that has seen its better days. Total and complete rebuild is definitely needed.
Plan for this build is a street Queen as i have another off road toy. Going with a 5.3 and 4l60e auto trans, NP241C transfer case. Found some wide track axles and put 4.10 gears in them. Only running 33 inch tires... Also did the one piece rear axle. It came with a half cab in decent shape plus i have a new soft top ready to go.
Bought a brand new tub from Overland Willy. Picked up a an old frame from a forum member.
Why would anyone want to run the E85 fuel? The only advantage I see is if there is nothing else available. My Chevy 2500 HD has the capability so I tried it. I had considerably less power and went from averaging 12 mpg to 9 mpg. Harldly worth the $0.15 per gallon savings?