Best way to stabilize cold starts with E85 on 3.5 ecoboost??

[Perna00]

2020 f-150 upgraded pump and port injectors for full e85 capability w/ flex enabled. Now that it?s getting colder down here in Savannah, my truck is starting fine but the first 10-15 seconds are stumbling and almost stalling out. I tried changing the percentages on PI/DI without success. From my reading, I?m finding that the most common reason is the need for addition fuel while cold/warm fuel tables are used. I did find some fueling tables under my open loop/warm start maps. Most the temperatures are still calling for around one lambda. What should I adjust them to to try to stabilize my situation? There are two separate tables but I still have to find out if the flex fuel enabled it into the equations or not. I was told that the cold start emission reduction could also play a part with it, but it can only change the percentage of port versus direct injections. Has anyone else got any advice or know of a way I could try to stabilize starting?

[Davem3261]

fuel>open loop>lost fuel. Add about 20% to base when the coolant temp is low. Add some to the decay so it takes longer to come out. Turn off flex fuel. It does not work well with an ecoboost. There is no way to add timing like you can in a 5.0. Any tuner will NOT do a flex tune for ecoboost. I know it will run with flex on but just dont do it.

[Perna00]

Thank you greatly for the response! I was messing with a few variables and I ended up adding about 20% more fuel to my ?fuel base cold FFV? table up to about 90 degrees and 10% up to 116 degrees under .3 load. I just did it tonight and the first start was perfect. I?m not sure if that is a solid solution but I?m still learning. I do use the flex fuel option since I?m not the closest to E85 and sometime I do have to mix premium fuel with it when the station is out or I?m not close enough. It is a shame I can?t adjust the timing based on FFV but I am running some advanced timing while still being conservative for a flex mix.

Now I do have to ask about the lost fuel parameters. They are completely new to me. To my understanding, it is a mild adjustment to compensate for fuel on a cold engine?? It seams like it is only around 1%-3% so a pretty small change. I see the decay is a modifier I?m assuming works based on temperature and time (which might be perfect since my issue is between 3-10 seconds). It appears that is also a 1%-3% change. Do you believe these tables are going to be the most beneficial and is around 10% a good modifier for my situation. Thanks again for any info you can provide. PM me if needed.

[Davem3261]

Not sure exactly what your doing because your not posting up your tune or any logs. First turn off flex fuel. I would be interested to see what your LSPI tables look like. If you are running E85 then putting in just 93 when you need to your timing must be a little over stock and your not taking advantage of what the E85 can do. If I were you I would tune for E30 and set your LSPI tables to reduce boost when your on 93. This should allow you to add 5 degrees under load. When you fill with 93 the LSPI tables can reduce boost until you fill with ethanol again. E30 requires about 10% more fuel over pump gas, let the fuel trims take care of that. Once again this is not a 5.0 and your can't add timing based on ethanol content. There is no sense to running E85 with some advanced timing.

[Perna00]

Thank you for the assistance (again!). I've attached my current tune to the thread. The vehicle doesn't sputter as soon as I start it now. It does have one split second sputter after about 4-5 seconds but only once. I'll have to record a log and adjust my PID's for fueling info to try to troubleshoot it. I do like that it is only adjusted in the FFV cold start modifiers so that it wouldn't have any adjustments with regular fueling. I'll attach a log after I get a chance to start it from cold and record it.

My main plan for the tune was to create a flex fuel tune that would max out performance with E-85 but would still be safe if I had to use 91/93 based on availability. Unfortunately, there isn't a FFV chart for timing, so it is difficult to create a specific flex tune for it. I've currently advanced all my borderline tables 5 degrees (what do you believe if a realistic borderline advancement number with E85?) but haven't adjusted MBT at all for the properties of E85. I'm not sure if I will either since I'm already around 600+ Torque and don't want to push the limit of the engine (650 seems to be internal limits from research). I've capped boost around 20 PSI with a larger intercooler so I'm pretty happy with the performance of this flex tune unless I'm really missing out on something I could take advantage of. Ideally, as soon as I get this startup smooth, I'd like to save my tune as a final that I could use for E-85 and it'll still be safe for 91/93 and possibly make a tune separately targeting E85 only.

November 9th cold start fix.hpt

[Perna00]

Here is the cold start log. It didn't hiccup at all. I didn't realize how high the SAE load chart was during startup. I don't believe I added enough fuel higher in the tables for it but let me know what you think please. Thanks in advance for any advice you can give.

Cold start nov 11.hpl

[Perna00]

I finally got a chance to mess with the cold Tables. I found out that even though there is a flex fuel cold start table, it does not work with the truck even when it is pure E85. I had to adjust the normal cold start fuel tables. The 20% did get it to start Smoothly however, after about five seconds, it would cause a slight miss from the decay. Right now it is around .01 decay rate. What should it be adjusted to? It shows in lambda adjustments and seconds on the side chart, but does it compound where I need to space them out more or how would you recommend?

[Davem3261]

Screenshot 2023-11-25 083121.png
All of these tables are increased by 20% on my E50 tune only below 100 degrees. I would go 30% on E85.

[Perna00]

Thanks again. I was messing with the cold start open loop tables. I understand them but not much about the “lost fuel”. I’ll adjust mine and test it out but would you mind explaining the effects of them for learning purposes…?

[Perna00]

I adjusted all 5 of the lost fuel tables by a 25% increase and it started rougher and almost stalled afterwards. I think I need to adjust the decay rates. Maybe the extra cold/start up is fine since it started smoother but needs that longer decay so be able to feather in.

[veeefour]

Best experience with using Cold Enrich. Decay table.

[Perna00]

I wasn’t able to get the lost fuel to work so I went back to the cold start open loop and added 25% more fuel to tables under 100 degrees and zeroed out the cold enrich decay to see if it was removing the extra fuel too quickly. It was around 55 degrees this morning and it started great and idled pretty decently for the first 10 seconds where it stumbled before. I thought for a few seconds (3-5 seconds after starting) I heard a slight stutter but it wasn’t significant enough to be sure. I’ll have to try again later and will need to follow up with colder/warmer temperatures to tweak any tables that I need to.

[Davem3261]

Those are the only tables that are changed on my truck, keep in mind i am on E50. If you added to the open loop and lost fuel, you would be very rich. Try putting the open loop back to stock and just add to lost fuel. My truck starts fine with no stumbles and I am in the northeast.

[Perna00]

When you talked about the lost fuel, I ended up changing all my cold start tables back to stock and just added 25% more fueling to all the lost fuel charts. I started with just the main top two tables without success. I then did all 5 with no success. It pretty much always started but stumbled after about 3 seconds starting. Prior it stubbled immediately after starting but smoothed out. It seems to just change the timing of the stumble. I believe my issue was either I was too lean when it started (when I began this adjustment) or too lean after the decay began (after starting adjustments). It currently started fine but that is only one attempt around 55 degrees, so I'll probably end up having to adjust numbers after a few more trials. I'm running straight E85 so I know it has quite a bit to do with it. I'm down south in GA so I'm not even sure if they adjust for a "winter blend" down here. After a little research, I like the idea of the "lost fuel" since it impacts only the small amount of time after starting before it goes back to preset parameters, but the cold start fuel is giving me the best results so far. I data logged and it seems that the open loop for my truck after starting is only about 30 seconds before it switches to closed loop so I'm not too far out timewise into the enrichment cycle for the truck. The exhaust definitely smells richer but not to the point where it is discolored or black. Hopefully I'm not getting any wash-down with the cylinder walls.

[Davem3261]

I had Lund tune my GT350 on E85. It stumbles on every cold start even in the summer. I mentioned it to them and their reply was "thats how it goes with E85, I added fuel when its cold" It might not be possible.

[Perna00]

They might be 100% true with the ecoboost. I just tried starting mine again and it had a clean start but stubbled after a few seconds for about 2-3 additional seconds. I need to figure out what is causing it to see if it can be fixed.

[Davem3261]

Thats how my car starts on E85

[veeefour]

Try something like this:

image.png

[Perna00]

I’m assuming that with the 25% being added to all temperatures under 100 as the baseline fuel addition to cold start open loop?

[Perna00]

I went ahead and copied that chart to my cold start fuel decay. That seems to have made it quite a bit smoother although between 5 to 10 seconds, I still do have a very slight stumble but nothing that will throw any codes or check engine lights. That is with it being around 45? here. I’m also only adding about 25% more fuel to the cold start… Do you think it’d be better to go up to 30%? Or should I be happy as it is since it’s E85?