ls3 flex fuel leaning out on ethanol blend

[nooch8it]

Ls3 in a C6 with 1100cc injectors, car runs great on 93 pump gas and low boost ECS 1500 SC. walbro 450 intank pump and 044 external on hobb switch for boost, gm flex fuel sensor on return fuel line. The issue is I put 5 gallons of e85 in and now the car idles in the high 15s afr instead if high 14s like on 93. I just want to see if I missed something in the tune. Thanks Idle log and tune below

1100cc ff e45 ls3.hpte45 idle 1.hpl

[07GTS]

i have herd if there is any air in the return line that it can stuff with the reading..? i fitted mine to the feed line just to make sure

[nooch8it]

ok thanks, I have been running the flex fuel sensor for months and its dead on % wise. Im just concerned I missed a setting in the tune and that why its not fully compensating for the ethanol. Any one have a boosted ls3 running flex fuel to compare setting???? or a guru..... that can tell me I suck at flex fuel and what I need to look at. Thanks

[nooch8it]

I took the car out for a 20 min drive tonight and while it drives ok the stft are all over the place with a e45 blend. On 93 are with in -5 to 5 for the most part but now they swing way out of wack and I get a stft surger that I can see in the log and feel while driving. Only change from driving great to slight issue is e45 blend. input needed......the forum wont let me upload a 20min log or I would post it.

[GHuggins]

Only thing that I saw was you might want to make default frequency 65hz and comp change threshold 2%...

Other important things to keep in mind with ethanol and especially large injectors - injection timing will usually need changing to get bank to bank fueling closer and optimize atomization better - even with stock cams - if stock try advancing by adding to the ect table 12 degrees...

Then it almost looked like you might have a different iat sensor? If it's been moved to the intake manifold - you need to use a ZL1's biasing tables...

Otherwise I don't see anything that's going to drive it that lean with ethanol unless you have headers and need to dial in your O2's?

[nooch8it]

ok thanks GHuggins Ill try the suggestions you mentioned. My iat sensor is stock and still located in the maf. My ve map and stft are great on 93 so I feel like the pcm is just not adjusting for ethanol correctly. I have tuned other standalone ems systems with flex fuel sensors and you can control fueling by % based on ethanol content or use entirely separate fuel map for ethanol fueling......it seems like that's missing from the gm pcm or Im not seeing it. Thanks again.

[GHuggins]

stoic table is ethanol and you have it correct - there's also open loop ethanol tables - make sure under edit that your setup in advanced mode.

[nooch8it]

Its funny how I can look at something 50 times and think I understand it....... Thanks again. While looking over the tune a few things clicked....ah ha moment. It looks good and I think I see how to correct the stft swing. Then onto WOT. Any pointers on that would be great. thanks again

[sevinn]

Its funny how I can look at something 50 times and think I understand it....... Thanks again. While looking over the tune a few things clicked....ah ha moment. It looks good and I think I see how to correct the stft swing. Then onto WOT. Any pointers on that would be great. thanks again

For WOT just make sure you have PE set to what you really want it to be in EQ Ratio (Alcohol). In the tune you posted earlier it's set to a good deal more rich than your gas table. Really not much to it if all the right things were enabled for flex fuel in the tune.

[nooch8it]

yeah I have it way over inflated in the alcohol pe table, I use boost enrichment for my WOT fuel control so is should be good. Ill adjust the alcohol pe table before I test it out. Thanks

[LSxpwrdZ]

99% of the time if fueling is accurate with gas and off with ethanol and the sensor is reading content correctly the injector data is the problem. You have to realize that the factory ECM is only working in ratios of airflow to fuel flow. If one of those is skewed so will be the other.

[nooch8it]

99% of the time if fueling is accurate with gas and off with ethanol and the sensor is reading content correctly the injector data is the problem. You have to realize that the factory ECM is only working in ratios of airflow to fuel flow. If one of those is skewed so will be the other.

Im hoping this is not the issue because not one person on the planet seems to have the best injector data or scaling method for these injectors (fuel injector clinic 1100cc). I have had a few "pro" tuners attempt to tune the car and injector data and non of them could come even close to my own tuning and scaling. My tune on 93 runs great with zero issues or surging......all other attempts resulted in huge afr swings, surging or horrible trans flaring on shifts. I topped the car off with e85 last night and will take it out today for some logging. I'm ready to put some real boost and timing into this thing so I'll do my best to get it sorted. Thanks

[nooch8it]

How many of you guys running flex fuel are keeping the ltft on? I have been running with no ltft on due to wot tuning and it adding fuel but with flex fuel working and e85 in the tank it seems to help the pcm adjust for blended fuel. The cars afr at wot on 5-6psi of boost on 93 pump would hang around 11.5-11.7 with peak timing of 11 degrees. With e55 blend in the tank and no tune changes the afr at wot will swing from lower 11s to low 12s (I can correct this by tuning the ve map but then my 93 pump tune is off). I turned the ltft on and drove the car for 5 mins then did a wot pull and it added the needed fuel for ethanol and moved the timing up to 14.5 degrees..... Any of you guys see the same results? either way it seems to have allowed the pcm to work its magic. Thanks

[sevinn]

I leave mine on. I'm na though but that shouldn't matter here.

I didn't have to change anything when I added my flex fuel setup other than the required changes to get it working at all. I still get some fuel trim issues when I have big composition percentage jumps because I probably need to work on my transition volumes, but I never bothered because it was only a few percent off for a few minutes.

I'm starting to be a believer that your issues are due to injector data.

[ddtech]

Turn LTFTs OFF if you have long tubes.

[sevinn]

Turn LTFTs OFF if you have long tubes.

Completely unnecessary especially if you properly tune your o2s.

[LSxpwrdZ]

Im hoping this is not the issue because not one person on the planet seems to have the best injector data or scaling method for these injectors (fuel injector clinic 1100cc). I have had a few "pro" tuners attempt to tune the car and injector data and non of them could come even close to my own tuning and scaling. My tune on 93 runs great with zero issues or surging......all other attempts resulted in huge afr swings, surging or horrible trans flaring on shifts. I topped the car off with e85 last night and will take it out today for some logging. I'm ready to put some real boost and timing into this thing so I'll do my best to get it sorted. Thanks

Yeah their data sucks. Their ASNU1650 data also sucks. When the data has discrepancies in it's own data spreadsheet I tend to not trust any of it.

[schpenxel]

Yeah, injector data is more than likely the problem. With ID's injectors I've never had any issues going from E10 to E85.. it adjusts perfectly, fuel trims stay next to 0, lambda error stays next to 0. Honestly I was amazed how well it worked

The problem is, more than likely, those injectors.

[schpenxel]

One other thing that doesn't make sense to me

In most of the log the narrowband O2's are cycling like normal, but the wideband is still reading in the 15's.

I would expect it to be cycling over/under 14.7 when in closed loop.. so that makes me wonder if your wideband is accurate. In closed loop it should be bouncing back and forth over/under 14.7

[GHuggins]

Or maybe o2s are incorrectly tuned or transients were messed with?