Misfire issue when running ethanol on flex tune

Hey everyone,

I've been playing with some ethanol on a very basic flex tune I made. Nothing wild, just enabled flex and then upped the base timing. It was running great, on the first fill, and the second fill, but on the third full fill of e85 I started throwing random misfire codes, and at one point got a flashing MIL from a transient but heavy Cylinder 2 dead miss. I believe that it was triggered by finally reaching full flex fuel ethanol concentration. I burned the tank halfway down and filled with premium and it has gone back to normal. However I don't know what I'm doing wrong, I've uploaded the files here. One uses stock gasoline timing, and the other steals some timing from the F150 but with a neutered multiplier. Both maintain stock gasoline MBT tables.

Attachment 134133
Attachment 134134
Attachment 134135
Attachment 134136

If anyone would be willing to briefly look at any of these files I'd appreciate any insight greatly. My guess right now is that my target lambda is off causing too rich of a mixture, but I'm not 100% sure. I've used the 02_ file before but never with more than 50% ethanol, and it worked fine.

Mainly cold start issues?

Probably need to figure out why it's rapidly switching spark and torque source.

Upload the F-150 file you were referencing.

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Originally Posted by engineermike

Mainly cold start issues?

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Yes the code that kept coming back was misfires in the first 1000 revolutions. There was a cylinder 2 misfire code but that only showed one time. What does that indicate? I was guessing spark plugs, mine are stock heat range and gap.

EDIT: The F150 uses identical plugs and gap, so it should be possible to run as is.

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Originally Posted by SiriusC1024

Probably need to figure out why it's rapidly switching spark and torque source.

Upload the F-150 file you were referencing.

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F150 file I used is here:Attachment 134197

I believe I copied all of the flex related tables. You'll also be able to see what I did with the timing, I didn't wanna jump right into it so I tried adding less timing overall by reducing the max multiplier from 1.75 to 1. Weirdly enough the base timing seems lower when compared to my gas tunes, or even compared to the "stock timing ethanol" tune.

Spark and torque are locked at Borderline and Driver demand during the pull, but I noticed that around 5700RPM in the pull the Fuel enrichment kicks up hard to Exhaust temp. Enrich. Which I'm not familiar with.

For what it's worth, I get the same on my 2.3 Ecoboost Mustang, only when it gets over 20% alcohol does it start giving "misfire in first 1000 revolutions".
I don't have a solution yet, haven't had time to look into it, but I do know it runs pretty lean during cold start catalyst warm up, so I'm fairly sure it's one of the cold start FFV tables.

When I started playing with flex tuning I noticed terrible idle and misfires after startup when it was still in open loop. I realized my maf cal was pretty bad so I fixed that on gasoline and now I’ve back on e85 and will know more soon.

I did notice one odd thing though. My inferred afr had matured at 11.0. I am using nvram for initial value, but upon initial startup the inferred afr showed as 14.0 in the log. The instant it switched to closed loop, the inferred afr changed to the previously matured value of 11.0. So far I haven’t been able to determine why it’s doing that or if it’s even contributing to misfires but I’ll do some testing soon. If I can’t get it to start up using the matured value, then I’ll figure out a bandaid.

Quote:

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Originally Posted by engineermike

When I started playing with flex tuning I noticed terrible idle and misfires after startup when it was still in open loop. I realized my maf cal was pretty bad so I fixed that on gasoline and now I?ve back on e85 and will know more soon.

I did notice one odd thing though. My inferred afr had matured at 11.0. I am using nvram for initial value, but upon initial startup the inferred afr showed as 14.0 in the log. The instant it switched to closed loop, the inferred afr changed to the previously matured value of 11.0. So far I haven?t been able to determine why it?s doing that or if it?s even contributing to misfires but I?ll do some testing soon. If I can?t get it to start up using the matured value, then I?ll figure out a bandaid.

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You know what's funny is that mine also stopped at 11:1 or 60%, which I found odd because the pump ethanol near me is typically 75-80% in the summer its usually close to 85%. My fuel trims were good though, so I just assumed it was accurate or some error in the calculation. I put in a little under half tank of "E85" on top of premium and it learned to 50%, then I put in 10 gallons of "e85" on top of that 50% blend and it only went up to 60%, I found that strange as the initial jump to 50% would indicate a very high alcohol percentage, but the second jump form 50 to 60% would indicate a very low alcohol percentage.

I have a Fuel-It Bluetooth gauge from my previous car, it would be interesting to compare the measured value to the inferred value and see how accurate it is. If the car thinks it has 60% E, but its really >80%, I could see that maybe being an issue. Especially since so many tables use that percentage to change things.

I've seen the 14:1 thing too, key on engine off, the learned AFR was flickering between 11 and 14, started the car and locked at 11. Also set to NVRAM.

There is definitely something up though, a 40 minute highway drive yielded nearly 1500 logged misfires on full strength pump e85, that same trip with an e20 blend in the tank yielded only 100.

Perhaps a leaner AFR would help, or pushing around the DI/PI blend. I'm just guessing now though, I have no evidence to back that idea up.

did you make sure in the fuel pump tab you copied over the standard fuel pressure over to the flex tables. if not the ffv fuel pressure tables are only at like 725 or so max

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Originally Posted by Bill88stang

did you make sure in the fuel pump tab you copied over the standard fuel pressure over to the flex tables. if not the ffv fuel pressure tables are only at like 725 or so max

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Yep, 32087, 7365, 7328,and 7336 are all the same as their gasoline counterparts. I could potentially command slightly higher pressure at lower RPMs, to help with atomization and ignition. Hmmmm.....

The way I made this "flex" tune was by copying any table from the F150 that has the suffix "FFV" and enabling the toggle. If I did that, and left the timing alone would it be reasonable to expect the car to run correctly? Or does it require more messaging than what I described?