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Fuel trim review? I'm paranoid and need you guys ❤

How's my 2019 Si Coupe Running?

  • Looks fine, all in spec!

    Votes: 9 39.1%
  • Something is definitely wrong

    Votes: 5 21.7%
  • Maybe? Something might be off, need a pro to look

    Votes: 9 39.1%

  • Total voters
    23

Static_Awesome

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Hey all! I'm probably being paranoid about my fuel trims after installing the PRL FMIC kit. I see high STFT (+5-19) at idle sometimes, but otherwise it looks okay? I'm including a KTuner log of an idle, ease into first, then WOT through 4th, with cruising after, since I figure that's a good range of metrics for review. List of mods:

(2019 Civic Si Coupe)
27WON Intake
PRL FMIC Intercooler + Piping
Custom Straight-through (bend eliminate) Muffler Delete
TSP Stage 1 tune (Map 3 for this run), Rev hang ON

If anyone could take a peek and give me some insight as to whether it's running well or not, I'd really appreciate it. I've included a poll in case there's differing opinions. Thank you guys so much in advance! <3



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gtman

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It's hard to draw a conclusion from a one minute log. LTFT is fine. STFT is all over the place on the log. But again you need to do a longer log. Maybe 15 minutes plus.
 
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It's hard to draw a conclusion from a one minute log. LTFT is fine. STFT is all over the place on the log. But again you need to do a longer log. Maybe 15 minutes plus.
Gotcha, I'll take a longer drive with a mix of driving in it, and upload that as well. Thanks for you insight!
 
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Let’s keep this alive for scientific reasons ;)
Agreed! I'll be posting more logs soon, trying to find relevant data. For now, I noticed it's only showing enrichment (+STFT) when colder. This makes sense. Colder air, more airflow, more fuel is needed. Today when it was hot again, trims were back to "normal", IE leaning a bit out at idle.

Looking at scatter plots of WOT pulls, regular driving, and some cruising, there is no trend. It looks like there's variation in my driving and temps, leading to the ECU doing what it should: Keeping target AFR.

Speaking of AFRs: They're golden, within 0.10 of target almost all the time, typically less. Transition from WOT to less throttle, and vice versa, it sometimes blips. That's normal, I believe.

Boost leak is also ruled out. Target boost and actual boost were almost always the same, actual boost sometimes going a hair over target before EWG compensated.

To the "something is definitely wrong" trolls, chime in, don't be afraid. ;)
 

randomisjustfine

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@Static_Awesome by any chance you monitor stft/ltft live? ie: tunerview app or similar?

Since tunerview memorizes min/max values, I do have -70 on short term and -88 on long term stored there. Positive value on ltft is 0 and stft is at 15. I have no clue where this coming from, can’t catch it. It seems like it might be coming in clutch in situations before downshifting.

Although 99.9% of a time ltft is -2 to 0 and stft is around 0 as well. Although I can spike stft with 0% tps to 1%< then back to 0% ie: when starting to accelerate and letting it go because someone is suddenly braking in front of me.

I have no clue how fuel trims work besides that it compensates lack of fuel/lack of air situations. I really wanna better understand all these tiny spikes. If it’s kind of the same as knock control spikes, then according to Derek it doesn’t mean anything. Otherwise should I be worried or not.

It’s very similar situation with max/min values with vit stage1/tsp stage1. Although live numbers look better with one then another.

Waiting for more knowledgeable people to chime in.
 
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@Static_Awesome by any chance you monitor stft/ltft live? ie: tunerview app or similar?

Since tunerview memorizes min/max values, I do have -70 on short term and -88 on long term stored there. Positive value on ltft is 0 and stft is at 15. I have no clue where this coming from, can’t catch it. It seems like it might be coming in clutch in situations before downshifting.

Although 99.9% of a time ltft is -2 to 0 and stft is around 0 as well. Although I can spike stft with 0% tps to 1%< then back to 0% ie: when starting to accelerate and letting it go because someone is suddenly braking in front of me.

I have no clue how fuel trims work besides that it compensates lack of fuel/lack of air situations. I really wanna better understand all these tiny spikes. If it’s kind of the same as knock control spikes, then according to Derek it doesn’t mean anything. Otherwise should I be worried or not.

It’s very similar situation with max/min values with vit stage1/tsp stage1. Although live numbers look better with one then another.

Waiting for more knowledgeable people to chime in.
That's more variance than I've seen, but I haven't looked at the lifetime max/min. I have seen +20 and -20 on shift/WOT transition, but that's the only time. Typically I'm slightly leaning (-STFT) under high load. And +10-18 on idle in cold weather. I think we need expert opinion too, maybe @D-RobIMW can pitch in for sciences' sake? We're not as experienced on this platform, only having seen forums and our own cars, whereas the experts have seen tons!
 

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Just to clarify, by saying I can spike stft I meant I can get it to high single digits, not the -70 value. I don’t really see anything above single digits on stft. And ltft is rock solid -2 to 0.

I’m not really worried about my numbers, since I’m well within where I should be.

The only thing I am curious about is how to understand -70 and -88 spike that is stored in the memory.

I might flash my car back to factory and drive it for couple weeks. Gonna be on fresh oil too. Just wanna see how much of a difference is there between tsp/vit/stock :dunno:
 
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Update: It looks like it might be the TSP Stage 1's idle targets/closed loop, because it only shows this much of a difference in idle and FUEL STAT 2, which I think is closed loop. This log shows what I'm concerned about pretty well. That said, it's below a 14.7 AFR whenever this happens, and it's not under load... just burning fuel when it doesn't need to, really. Haha.

Edit: Apprently TSP Stage 1 runs on closed loop.... a lot? And uses STFT to adjust rather than inputs?

stft1.PNG
 

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Update: It looks like it might be the TSP Stage 1's idle targets/closed loop, because it only shows this much of a difference in idle and FUEL STAT 2, which I think is closed loop. This log shows what I'm concerned about pretty well. That said, it's below a 14.7 AFR whenever this happens, and it's not under load... just burning fuel when it doesn't need to, really. Haha.

Edit: Apprently TSP Stage 1 runs on closed loop.... a lot? And uses STFT to adjust rather than inputs?

stft1.PNG
Not trying to be a troll ;) but it does seem the car is trending very lean. Alot of benefit to ltrim could be had just with some idle AFM adjustments according to your screen shot. 18% is high.

Yes the cars can/will run closed loop until wot is acknowledged and even then sometimes it "could". Thats all controlled via afr targetting tables/ measured airflow wot trigger table.

The reason your scatter plots are that "all over" while the afr is remaining consistant is simply because the trims are doing their job.

The drawback to this is the rapid transitioning of increasing/decreasing injector pulsewidth which is not good for the injectors/drivers.
 
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Hey, input isn't trolling bro! It is definitely "lean" here. By "lean" I mean for some reason it's targeting a 13.0AFR in no load idle... Which is weird. in idle, cruising, regular, and spirited driving and WOT all show much less deviance. And the car runs in FUEL STAT 2 in WOT as well, see previous log. I very rarely see open loop in my logs, mainly seeing fuel cut or closed loop. I did a 45min log, used Google Sheets, and averaged the difference between AFR.CMD and AFR.ADJ as well as AFR, and average deviance is actually 0.05 towards rich, not lean. I exempted fuel cut scenarios (IF AFR.CMD > 19.9) so only open and closed loop samples were used.

It was 65,000 samples or so.
 
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Also, I can't adjust shit lol, it's a locked tune. Considering going to the KTuner 23PSI tune and seeing if this behavior is still there. Also, it may just be a single shitty tank of fuel, I just switched out from shady Citgo 93 to primo Shell 93, we'll see if the variance dips either way.

I may consider running open loop and close loop on the same 23PSI tune and see if it behaves differently. I'd like to hear from maybe @KTuner if their base maps are okay to run that way first, though.
 
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Update: Same behavior on KTuner +23PSI tune. Holds boost fine, trims just run high (10-25+ STFT) under low load, close to stoich or under 14.7 most of the time still. Still targeting 13 and under at idle sometimes... Weird. LTFT is still under 5.
 

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Pay specific attention to when the targets change and you'll start to notice the patterns. Super light pedal, almost not on throttle at all, mine targets 15.1.

When the idle first recovers from fuel cut no matter what mine would hang out around 12.5 to 13.0 afr (including targets) for what seemed to be a insanely long time.

I was told this is normal ECU behavior and the rich areas are a pre-throttle tip in function.
 

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What I find odd is how the OP is consistently lean. My trims tuned have always been slightly rich. LTFT generally is around -2 to -3 on the TSP Stage 1.
 

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