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Author Topic: audi a4 avj mafless lambda issue  (Read 617 times)
giorgosgoul791
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« on: August 18, 2026, 02:10:16 AM »

Hi everyone, i have an Audi A4 20vt avj engine, gtx 2867 turbo, maffless tune, bosch 630cc injectors, and all necesary peripherals.
The car face an issue, after almost 5000 rpm goes rich to 0,75 lambda. We have check everything. All components and sensors are new.
Returness fuel system replaced with normal fuel rail. I attach log, ori and tune file. Any help apreciated.
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_nameless
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« Reply #1 on: August 18, 2026, 08:31:06 AM »

*edit*
I had a look at the log and its utterly useless.

Unless its patched for a map sensor in the intake manifold, your "mafless" tune will always be wrong, you have no atmospheric density compensation. VCDS logs are garbage, you can not possibly find any issue with those crap 3 channel logs at such a slow capture speed. Im being blunt for a reason, sugar coating it wont help you. Fit a genuine maf sensor, get some real logs using vehical or me7 logger, and if closed loop is dropping out during full throttle, check your bts and knock correction. If bts is set too rich and request goes below the internal minimum lambda value, closed loop gets switched off. Same goes for knock correction, if the ecu is pulling a shit ton of timing and dumping fuel trying to save the engine, you will have the same result, lambda switched off.
« Last Edit: August 18, 2026, 08:44:51 AM by _nameless » Logged

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giorgosgoul791
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« Reply #2 on: August 18, 2026, 11:08:33 AM »

Thanks for the answer. To be clear, this car is not mine and I'm not the tuner. I made this topic to help a friend. Every 20vt here built with the same way, but this A4 doesn't work.
If you can check the file also. Thanks again.
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nyet
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« Reply #3 on: August 18, 2026, 12:05:59 PM »

install a MAF and stop fucking around. speed density is a total fail on any of these motors. It gets you literally nothing.

If you have a known good reference, compare logs.

I doubt that you have any properly running speed density car though.

it looks like you totally ignored all of _nameless' post which is dead on accurate.
« Last Edit: August 18, 2026, 12:08:17 PM by nyet » Logged

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giorgosgoul791
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« Reply #4 on: August 18, 2026, 02:43:44 PM »

install a MAF and stop fucking around. speed density is a total fail on any of these motors. It gets you literally nothing.

If you have a known good reference, compare logs.

I doubt that you have any properly running speed density car though.

it looks like you totally ignored all of _nameless' post which is dead on accurate.
sorry but i didnt ignore nameless post, i just try to find an explanation.
No, i havent any other log from other car. i know that another leon 20vt which follows the same mafless logic, works.
if you can help i will appreciate it. If you dont want to help plese dont be aggresive with me. im not the tuner of this car. i dont tune 20vt.
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_nameless
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« Reply #5 on: August 19, 2026, 01:50:20 PM »

Thanks for the answer. To be clear, this car is not mine and I'm not the tuner. I made this topic to help a friend. Every 20vt here built with the same way, but this A4 doesn't work.
If you can check the file also. Thanks again.
No, I wont check the file, why would I? It "doesn't work" because the tuning approach is shit and the file is too far off causing lambda control to drop out for one reason or another plain and simple. Tune the car better, take actual data logs not vcds garbage. I mean one of the blocks being logged was maf flow and you don't even have a maf plugged in.







sorry but i didnt ignore nameless post, i just try to find an explanation.
No, i havent any other log from other car. i know that another leon 20vt which follows the same mafless logic, works.
if you can help i will appreciate it. If you dont want to help plese dont be aggresive with me. im not the tuner of this car. i dont tune 20vt.
So, on a different car, different setup, different software version "it works"... And wtf does that have to do with this car?... Nothing. Also, if its not your car, you dont tune 1.8t engines whats the point of making the post?
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Audi A4 B6 1.8T (early + late) · AWV / AWP / AWW
· VR6 in beta and 07K in progress
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billkgr
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« Reply #6 on: August 19, 2026, 02:39:00 PM »

As a first step, you need to properly log your car.
Get ME7logger working.
VCDS will give you like 0.5hz polling, while ME7logger will do 100x the frequency.
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VWvinny
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« Reply #7 on: August 20, 2026, 05:19:00 AM »

Hi everyone, i have an Audi A4 20vt avj engine, gtx 2867 turbo, maffless tune, bosch 630cc injectors, and all necesary peripherals.
The car face an issue, after almost 5000 rpm goes rich to 0,75 lambda. We have check everything. All components and sensors are new.
Returness fuel system replaced with normal fuel rail. I attach log, ori and tune file. Any help apreciated.

Dont know who tune it but its not the best..
I think you have to check your fuel trims..
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