Unleashed tune, now how to blend E30?

There's a lot of argument about this on the Interw3b. Theoretically you'd need to know the precise amount of ethanol in your mix, and use an alcohol sensor (GM uses these on some of their flex fuel engines). Ford's own Flex Fuel system uses an inferred reading where it adjusts the stoich to different set points based on what E85 mix it thinks you are running. Some of GM's older flex fuel systems used an alcohol sensor in-line with the fuel to provide data to the PCM and adjusts the stoich accordingly. GM's newer flex fuel systems use the inferred approach that Ford has been using.

When GM started using wideband O2's on their GTDI engines, the fuel trims could actually swing quite a bit to adjust and accommodate for different ethanol blends. I've tested my Cobalt SS Turbo to 50% E85 without touching injector offset and the fuel trims would just adjust without any issues. In fact, from the factory that car was set for 0% Ethanol, so when I ran the Michigan standard fuel of E10, the fuel trims were always skewed from the get-go. My 2007 Mustang GT was the same way as it came with a factory stoich of 14.64 when the stoich for E10 is about 14.08 (newer Fords all have a base stoich setting of 14.08), so when I was tuning for my Steeda hot air intake, the trims were always skewed from the get-go... and I used an external wideband O2 sensor to assist. I even did a comparison between using the factory narrowbands in a special technique, with the Innovative Wideband O2, and they came out the same.

Back to the Fusion Sport / SHO and Ford's TC-1797/1791 ECU, I've tried both ways - adjusting stoich to match the E85 blend, or leaving it at 14.08 and letting the ECU adjust the short and long term trims. They came out about the same on the street and track. With stoich at 14.08, the fuel trims would just be larger to accommodate. With the stoich set closer, the fuel trims would be much closer to 0%. Because these systems run closed loop at WOT, the wideband O2s allow the fuel trims to adjust even at WOT - versus the older narrowband systems that run closed loop until you go WOT then it is open loop (falls back on the MAF transfer function / VE Model already programmed). Our newer Fords are all speed density (no MAF) with wideband O2s. I believe only the Mustang still uses a MAF sensor after 2017/2018. I know my 2018 Explorer XLT's airbox doesn't have a MAF sensor and is speed density, whereas the 2016 or 2017 Explorer still had a MAF sensor.

Hi gang. I don't want to be the killjoy of the group, but this information at least needs to be out there for everyone to know: Ford specifically prohibits use of E85 or above fuels.

From your Owners Manual:

"Note:Use of any fuel for which the vehicle was not designed can impair the emission control system, cause loss of vehicle performance, and cause damage to the engine which may not be covered by the vehicle Warranty.
Do not use:
•Diesel fuel.
•Fuels containing kerosene or paraffin.
•Fuel containing more than 15% ethanol or E85 fuel.
•Fuels containing methanol.
•Fuels containing metallic-based additives, including manganese-based compounds.
•Fuels containing the octane booster additive, methylcyclopentadienyl manganese tricarbonyl (MMT).
•Leaded fuel, using leaded fuel is prohibited by law."

It can/will damage the engine/fuel management systems.

Okay, it is out there now. Boring older guy out.

Good luck with whatever you decide to do.

Tone228 said:

Question for the guys running a E30 tune. I’ve had an Unleashed 93 performance tune for the past year or so and it’s been great. I also have an E30 tune on the programmer that I’ve never used because I’m not sure how to accurately blend E85 and 93 to get E30. FYI I have a E85 tester already. To my understanding you need to know exactly how much fuel is in the tank, how much ethanol is in the 93 gasoline and how close to 85% ethanol is in the E85. I seen some other tuned cars using a programmer that will tell you the exact amount of fuel that’s in the tank but unfortunately the programmer I received from Unleashed doesn’t have that capability to my knowledge.
Am I over thinking this? Do you just use a 3:10 ratio of E85 to E10 93 when filling up?

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I just filled up my second tank on my E30 tune. Here's how I do this:

Our tank size is 18 gallons right? So on the gas gauge the half tank mark is 9 gallons, the 1/4 tank mark is 4.5 gallons because that's half of 9 gallons, which is half of 18 gallons. Now without really completely emptying the tank when your car dies, and tracking the gallons - that's as close you're going to get.


Today for the fill up, I wasn't too far off. I was just a bit below the 1/4 mark so I assume that's maybe like 4 gallons or so. From my ethanol calculator I needed 4 gallons of E85 (at 85% Ethanol) and 10 gallons of 93 to make up 18 gallons of E30 mixture.

So I put 4.25 gallons (wasn't paying attention enough lol) in of E85 and the gas gauge went up to the half tank exactly. It took 8.25 gallons of 93 to fill up where the pump shuts off automatically after fill up.

Total it was 17.25 gallons. (9 gallons for the half tank mark + the 8.25 gallons to fill up completely from a half tank).

Now without really making your car die and figuring out the gallons the hard way, imo that's the closest you're going to get -so I am sticking to my method of approximating gallons from the gas gauge and the car is fine, and logs are great.


These are all approximations obviously as it's an electronic gas gauge. But should be really close or give you a good idea of how much is remaining.


The real problem is figuring out what Ethanol % the E85 is. It can range from 51%-90%. I highly recommend to get an E85 test kit online for $10, grab a sample and let it sit overnight to get an accurate reading and go from there.

I am also going to buy a handheld instant ethanol analyzer after I move in 2 weeks so I don't want and have an actual percentage I can plug into the calculator for a perfect mix.