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

How's my 2019 Si Coupe Running?

  • Looks fine, all in spec!

    Votes: 9 37.5%
  • Something is definitely wrong

    Votes: 5 20.8%
  • Maybe? Something might be off, need a pro to look

    Votes: 10 41.7%

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Andre80

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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.


My ltft is always at around -7, even though it is always around -7, both with TSP 1 / ktuner dual / ktuner stage 2 / Stock

I changed several fuel stations
I changed the air filter
I tightened all the pipes well

now I'm trying an injector cleaner, at the end of this cycle, I will also have done AB2 maintenance

and I will also replace sparkle plug

Then I will start testing everything from the beginning, the 95 ron, the 100 ron and I will return to contort the different tunes

We'll see if I have more data to see if it's normal

I've never seen LTFT at -2, just after flashing, after a few km it comes back to around -7
very few times I see the STFT going positively, and very little

and I admit I'm going crazy
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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.
My theory at the moment is the combination of intercooler, charge pipes, and intake is leading to a larger vacuum/low load intake volume, and the engine is trimming positive to compensate. I'm running larger charge pipes, and yes the MAF is where all things enter, but I'm also running less than 10 degrees above ambient at times, so it might be a density thing. KTuner says that in closed loop it uses MAF to Target a AFR, then trims to compensate based off of lamda and closed loop targets based off the wideband difference. Long story short, I think that based off more research and feedback I could benefit from a tune to have closer trims, but the tune and ECU are doing what they should: Compensating to hit target AFRs.
 
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Hey all! My spikes got worse, so I'm actually thinking it's a vacuum leak, since it's mainly at idle, and not as much at speed. And when it is, it's under negative MAP pressure. Since I haven't touched that many hoses with the PRL FMIC install, I'm going to undo, check, and redo all of the vacuum lines and breathers soon. I'll keep ya'll updated.
 

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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
What program are you guys using to open these files?
 


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Resecured all vacuum hoses and sensors, checked MAF, still no change. :'(
 

brandonckc

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Guys help me take a look at my datalog regarding fuel trim.
I had hondata and recently just flash "return to stock" and swap my K&N oped pod intake back to stock intake.
And i did a datalog just to see how a stock intake and stock map perform.

To my surprise, car run very rich. STFT at idle around -12 % to 17% and during partial throttle acceleration would climb up to -3%. NEVER went to positive value at all. At WOT stft is at 0.

Is this normal for a stock intake and stock map?
 

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Update: seems to only do it in cold weather. Yesterday, hours and hours in the heat.... absolutely normal, STFT +5 to -5, LTFT 0. Today, 60 degrees, +10 to +20 STFT, +5-10 LTFT. Super weird.
 
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Update. High positive STFT is reduced to acceptable levels with A/C on, still present during driving (mildly, almost always in spec when light throttle, +3-7 at even high rpms). Checked MAF sensor, breather, and intake connections, did water and smoke tests on intake, nothing appears wrong there.

Going to take the intercooler and all charge pipes back off, resecure, and see if it behaves better. It's a toss up since it holds boost, but it's the only idea I have left unless some hero pops up and gives me a good idea. :)
 

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Hi all,

Recently uploaded the tsp stage 1 race maf non si tune and i am still learning about figures so i just wanted to check im running ok. Are my fuel trims in limit? This is after a 40minute drive of eco and sport mode in map 3 and then just parked on the drive at idle. Also i noticed when in sport or eco and i go WOT then off the gas i notice the ltft jump to like 25 then drop to 0 as im coasting slightly down the motorway. Are these experiences normal?

Honda Civic 10th gen Fuel trim review? I'm paranoid and need you guys ❤ 20191129_141458
 


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** edit ** my stft jumps to 25.
That's somewhat normal during shifting/transitioning, since the system isn't burning some of the fuel that's already been delivered for a split second. And your trims look really close to mine actually, I think we're worrying too much probably. Dumb question... Do you have a Race MAF? If not you need to use the other tune

If you do have a Race MAF, the only thing you can really monitor long-term is the LTFT. Temps, AFR, and STFT are going to change with speed and throttle. During WOT you should see under 12 AFR. LESS AFR means more fuel, higher AFR means less fuel, with 14.7 being neither rich nor lean.... But don't think you should always see 14.7, rich is safer under load without a really good tuner, and a really good tuner wouldn't let you run that lean under load either.
 

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That's somewhat normal during shifting/transitioning, since the system isn't burning some of the fuel that's already been delivered for a split second. And your trims look really close to mine actually, I think we're worrying too much probably. Dumb question... Do you have a Race MAF? If not you need to use the other tune

If you do have a Race MAF, the only thing you can really monitor long-term is the LTFT. Temps, AFR, and STFT are going to change with speed and throttle. During WOT you should see under 12 AFR. LESS AFR means more fuel, higher AFR means less fuel, with 14.7 being neither rich nor lean.... But don't think you should always see 14.7, rich is safer under load without a really good tuner, and a really good tuner wouldn't let you run that lean under load either.
Yes i am running the race maf set up and my afr drop below 14.7 when more throttle is applied so it does sound like i am worrying over nothing but i thought its best to check with the experts :) before running this tune i was actually running a custom tune by a tuner in the uk and i was achieving great power but it was just not functional enough at low speeds in traffic as the throttle is way too responsive so until i am able to send him logs for him to adjust, i thought i would go back to this tune and in all honestly although it is not as powerful, it is so much smoother and nicer to drive on. I was tempted to get derek to do me a remote tune but im worried that to feel the extra power, the tuners have to enable all quick enables to the highest and i dont like the outcome of that.?
 

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any more updates? My car is running tsp1 with cobra street and ltft is always around -7 as well. I emailed Corey from two step and he assured me that DRob said this was a normal behavior. Even ktuner on one of the forums that Honda's factory settings tend to run a bit rich.
 


 


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