NefMoto > Noob Zone > Noob Questions (Moderator: turboat) > High STFT during WOT / lack of fuel
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Author Topic: High STFT during WOT / lack of fuel  (Read 1618 times)
Gal_Anonim
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« on: January 18, 2025, 07:40:17 AM »
I have a little tuning novice problem and I need your advice. The patient is an Audi A3 8L 1.8t Quattro that I am learning tuning on. The car has a Sytec SYT420G fuel pump and fuel injectors replaced with 550cc Bosch 0280158117.
Used the following TVUB as well:
8v - 2.7
10v - 1.54
12v - 1.12
14v - .73
16v - .523

KRKTE = 0.05450
FKKVS = flat 1
KFLF = flat 1
LTFT corrections via Group 032: 001F (rkat_w), 0021 (fra_w) are -0.2% and -0.8%. The problem is during WOT in open loop. During WOT there is a lack of fuel from 4000rpm and STFT corrections reach 25%. Attached is a log from yesterday's ride.

Please advise because I don't know what this lack of fuel is caused by a faulty pump/PFR or does it only require tuning some parameter FKKVS/KFLF? which is related to replacing fuel injectors.
Please advise what to do next
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Gal_Anonim
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« Reply #1 on: January 19, 2025, 06:34:08 AM »
Today I added some fuel using KFLF and made another log in the attachment below. Please advise what I can improve because this time it's not the fuel that's blocking me but the ignition reversal? I intend to make fuel corrections today using FKKVS but I'm worried about the inability to reach 6800rpm. Any advice?
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Leonhard
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« Reply #2 on: January 19, 2025, 10:02:05 AM »
These 117 injectors are quite "non linear" but still a good choice for 1.8T inlet.
Leave KFLF flat 1 and work just with FKKVS.
Lower KRKTE until you reach factor 0.9 or even 0.85 at idle / part load area within FKKVS.
you might get factors at full load up to 1.20.
For FKKVS tuning you need to log TE [ms] (measuring group 02).

I use these TVUB for 117 injectors:

V   ms
8   2.12
10   1.33
12   0.92
14   0.67
16   0.41
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fknbrkn
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mk4 1.8T AUM
« Reply #3 on: January 19, 2025, 11:28:46 AM »
Quote from: Leonhard on January 19, 2025, 10:02:05 AM
These 117 injectors are quite "non linear" but still a good choice for 1.8T inlet.
Leave KFLF flat 1 and work just with FKKVS.
Lower KRKTE until you reach factor 0.9 or even 0.85 at idle / part load area within FKKVS.
you might get factors at full load up to 1.20.
For FKKVS tuning you need to log TE [ms] (measuring group 02).

I use these TVUB for 117 injectors:

V   ms
8   2.12
10   1.33
12   0.92
14   0.67
16   0.41

if you get 20% fr_w during WOT then its definetely not an injectors issue  Wink
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Gal_Anonim
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« Reply #4 on: January 20, 2025, 02:30:56 AM »
I have a question for more experienced tuners, bosch 550cc 0280158117 injectors require such corrections of 20-25% at the bottom and top of the revs or is there something wrong with my fuel system? The second question is a result of the first one, can I make corrections KFLF 1.25 for revs from 4000?
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fknbrkn
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mk4 1.8T AUM
« Reply #5 on: January 20, 2025, 02:57:20 AM »
Quote from: Gal_Anonim on January 20, 2025, 02:30:56 AM
I have a question for more experienced tuners, bosch 550cc 0280158117 injectors require such corrections of 20-25% at the bottom and top of the revs or is there something wrong with my fuel system? The second question is a result of the first one, can I make corrections KFLF 1.25 for revs from 4000?


ps_w goes skyhigh and MAF readings way too high for that boost pressure
thats the reason of fueling deviations
fueling corrections should bt made by FKKVS while KFLF used for specified lambda at open loop iirc

fix the issue, read my previous post
« Last Edit: January 20, 2025, 07:09:09 AM by fknbrkn » Logged
prj
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« Reply #6 on: January 20, 2025, 06:36:19 AM »
Quote from: Gal_Anonim on January 20, 2025, 02:30:56 AM
I have a question for more experienced tuners, bosch 550cc 0280158117 injectors require such corrections of 20-25% at the bottom and top of the revs or is there something wrong with my fuel system? The second question is a result of the first one, can I make corrections KFLF 1.25 for revs from 4000?

Great example of why you pressure test your intake and verify your fuel pressure before you start tuning.
Right now all you have done is wasted time messing around with something that clearly has hardware issues.
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Gal_Anonim
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« Reply #7 on: February 09, 2025, 10:25:02 AM »
Thank you all for your comments and advice. It actually turned out that I had a cracked intercooler hence my problems with the car for which I blamed the fuel injectors. After repairing the intake my set up generated such values. As you can see the limitation is the K03s turbo.
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