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Author Topic: Load increase → Actual Afr leaner  (Read 1783 times)
K92
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« on: January 20, 2023, 12:38:09 PM »

Car: Golf 4 4motion 1.8 ( fuelpump original )
Engine: 1.8T 110kw
Audi TT BAM injectors

Every time, i adjust IRL / IOP maps and increase load actual afr goes alot leaner, what could be the problem ?
Idle and Part trims are 0%, but WOT goes ~ +25
We also tested fuel pressure. At start ~2.9-3bar and drops to ~2.5 bar
Could the issue be fuel pump ?



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fknbrkn
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mk4 1.8T AUM


« Reply #1 on: January 20, 2023, 05:34:09 PM »

Fuel pressure should follow simple rule: fpr pressure + manifold pressure
I.e. at idle 3 - 0.7 = 2.3, at wot 3+0.7=3.7
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prj
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« Reply #2 on: January 20, 2023, 05:36:38 PM »

And fuel pressure should be measured on full load.
Measuring it at idle tells you absolutely nothing about it.
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K92
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« Reply #3 on: January 21, 2023, 01:04:02 AM »

These numbers were tested on full load. So lets say if im driving with 1bar boost and 3bar fpr on full load fuel gauge should hold 4 bar of fuel pressure ?
Then it seems i am  lacking 1+ bar on load
« Last Edit: January 21, 2023, 02:00:33 AM by K92 » Logged
fknbrkn
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mk4 1.8T AUM


« Reply #4 on: January 21, 2023, 04:09:02 AM »

Check fpr vac line
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IamwhoIam
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« Reply #5 on: January 21, 2023, 04:36:19 AM »

These numbers were tested on full load. So lets say if im driving with 1bar boost and 3bar fpr on full load fuel gauge should hold 4 bar of fuel pressure ?
Then it seems i am  lacking 1+ bar on load

This sounds like you need to give this car a complete checkover, and I'm pretty sure you'll need a fuel pump (upgrade possibly). Also, original pump, how about the fuel filter? probably never changed either, but hey yeah go on and bolt on injectors, turbos etc and go to town on it to make all the powerzzzzzzzzzzzz
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I have no logs because I have a boost gauge (makes things easier)
prj
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« Reply #6 on: January 21, 2023, 05:50:46 AM »

These numbers were tested on full load. So lets say if im driving with 1bar boost and 3bar fpr on full load fuel gauge should hold 4 bar of fuel pressure ?
Then it seems i am  lacking 1+ bar on load
Correct. And you need to fix that first before doing any more "full load" unless you want to put a hole in the block Smiley
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K92
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« Reply #7 on: January 27, 2023, 10:51:51 AM »

Turned out to be bad/weak fuel pump.
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