Did something stupid...put 6 gallons of E85 in my Mustang with stock Ford Performance Power kit tune

[Jjmoberg]

Like most of the 2 went into the half tank of ~5?

Now that would be a reason to always top off i guess.

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[Jjmoberg]

Now that would be a reason to always top off i guess.

Other issue I have is the E85 near me is at a Caseys and the 93 is about 5 miles from there. I dont really trust the Caseys 93. I dont think its Top Tier. So I sure as hell cant put 2 gallons of E on an empty tank and then drive over that to the other spot. So if i routinely add the 93 first on an empty tank and then drive and get 2-3 gallons of E, is what happened this time gonna happen every time…?

 

[K4fxd]

So if i routinely add the 93 first on an empty tank and then drive and get 2-3 gallons of E, is what happened this time gonna happen every time…?

I wouldn't think so. Is your car currently tuned by someone?

 

[ZXMustang]

I can do the math with my head or a calculator. But where do you get the actual fuel tank remaining volume %?

I have a PID in HP tuner that shows the exact percentage.

 

[Jjmoberg]

I wouldn't think so. Is your car currently tuned by someone?

Nope. Thinking of the Lund user selectable E vs Wengerd 93 and use the method we are discussing here to run E20-30 ish. Im gonna get the Fuel It kit either way.

 

[ZXMustang]

You can keep the comments about it being dumb to yourself. Its only dumb if you dont think about it. E would only be off the chart if you had 1 gallon of E10 in there and just put some E85 in there and just drove off.

Math isnt hard. I made some reasonable assumptions. The gauge said around 2/3 full. If i had 10 gallons of 93E10 in there and added 2 gallons of full on E85 that would be E22.5. Which according to this thread should have been ok. Now if my fuel gauge is way off and there was only 8 gallons in there then id be at E35 if it was full on E85 at the pump. But as everyone in this thread has said its not like its actually running lean.

In the end to do this without guessing we need to know the exact amount of fuel in the tank and its E content and the E content of both the E85 and 93 we are putting in. We dont really know any of those things without an E sensor on the car and testing at the pump. But we still wouldn't know exactly how much we have in the tank. So its an educated guess either way.

I will get an idea moving forward of what the E is in the tank with the Fuel It kit. Now that i have done it once i will only do it when i am near empty and go to full. Its not like what i assumed was ridiculous. Had i put in 1.5 gallons it may have well been fine. But tank over tank as your e climbs to around 30, you will need to add a bit less E85 at the pump unless you fill up at the ragged edge of totally empty.

There is no mathematical difference between adding 2 gallons of E85 to 10 gallons of known 93E10 already in your tank, or adding 2.5 gallons of E and 12.5 gallons of 93E10 to a totally empty tank.

Sorry for the dumb comment but clearly your car didnt like what you did. You were off the rich scale into the MIL territory and you got a check engine light. So you werent at 22.5 or whatever your napkin math told you. The car can easily add +30 or more fuel with the fuel trims. And you were over that. And at an e10 stoich, you were probably much closer to e40. I see +25 when I run e30 on a 14.08 stoich. I've been tuning my car on my own, so at this point I just change the stoich to 13.00 and my trims are usually close if not dead nuts.

 

[Jjmoberg]

Sorry for the dumb comment but clearly your car didnt like what you did. You were off the rich scale into the MIL territory and you got a check engine light. So you werent at 22.5 or whatever your napkin math told you. The car can easily add +30 or more fuel with the fuel trims. And you were over that. And at an e10 stoich, you were probably much closer to e40. I see +25 when I run e30 on a 14.08 stoich. I've been tuning my car on my own, so at this point I just change the stoich to 13.00 and my trims are usually close if not dead nuts.

AFT is reading 14.1/14.2 at idle as we speak

Wonder if my trims may be a bit positive normally due to my Soler ported TB.

 

[Jjmoberg]

Id buy all the PCMt stuff if i thought i could have the time to learn to self tune. Math i am good at, computers not so much!

 

[ZXMustang]

AFT is reading 14.1/14.2 at idle as we speak

Wonder if my trims may be a bit positive normally due to my Soler ported TB.

Yeah the car should keep stoich, but its adding fuel on the back side to do so. If you hit the MIL threshold to how much its set to add before you get a check engine light, then you will pop that light. The AFR on the dash might still be good, but your trims might be tapped or about to be. At idle and light throttle, you should be ok. But for the love of god, dont go wot and PRAY your maf v per table is dead nuts accurate. The car can only do so much.

Again always just run it down to E if you can and start the calculation from there. Look at the screen cap of the app I posted. It will give you all the options to get the mix right without a sensor. Its been awesome for me as long as the maf is correct and the E tests what I say it is.

 

[K4fxd]

AFT is reading 14.1/14.2 at idle as we speak

This is normal.


Another problem with the split saddle tanks. Since you didn't top off all your E went into the driver side tank. A flex tune would solve this.

I've never tried adding E without also filling the tank.

Thanks for posting.

 

[ZXMustang]

This is normal.


Another problem with the split saddle tanks. Since you didn't top off all your E went into the driver side tank. A flex tune would solve this.

I've never tried adding E without also filling the tank.

Thanks for posting.

good luck with that. Flex tunes are iffy at best. They have the majority of the F150 logic, but not all of it. There is quite a bit missing in the mustang versions vs the F150. Its not fool proof by any means. I've seen cars mature fuel trims way too fast, or over mature the AFR due to DFCO making the car go 2.0 lean on decel. That pushes down the AFR artificially and will cause your car to run negative trims until the next fuel up. With flex tunes, the most consistent way to manage them is to fill up, then let it idle in a stationary place for 10-15 minutes. That will let the car stabilize itself and run up/down the AFR as the new blend makes it way through the fuel system.

 

[Jjmoberg]

This is normal.


Another problem with the split saddle tanks. Since you didn't top off all your E went into the driver side tank. A flex tune would solve this.

I've never tried adding E without also filling the tank.

Thanks for posting.

I guess the next question then is given that i have to get E and 93 at 2 spots will this happen again on the factory tune if i put 13 gallons of 93 in and drive to get 2 gallons of E85…? Or will it mix into both tanks after the E fill?

 

[ZXMustang]

This is a video of my log of my car learning from e9 to about e77 I think it was. You can see how the car does it in real time.

 

[Jjmoberg]

good luck with that. Flex tunes are iffy at best. They have the majority of the F150 logic, but not all of it. There is quite a bit missing in the mustang versions vs the F150. Its not fool proof by any means. I've seen cars mature fuel trims way too fast, or over mature the AFR due to DFCO making the car go 2.0 lean on decel. That pushes down the AFR artificially and will cause your car to run negative trims until the next fuel up. With flex tunes, the most consistent way to manage them is to fill up, then let it idle in a stationary place for 10-15 minutes. That will let the car stabilize itself and run up/down the AFR as the new blend makes it way through the fuel system.

I wont do a flex based on all i have learned. Will be user selectable or 93 plus a bit of extra E.

 

[I Bleed Ford Blue]

Why can't someone just copy and paste the entire flex tune from an F150 and then tweak it for use on a mustang 5.0? Then you would have a true flex tune.

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