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Author Topic: ps_w lot higher than pvdks_w with stock MAF A4 1.8T  (Read 294 times)
damianalex
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A4 B7 1.8T 8E0909518AQ 0020


« on: December 11, 2024, 02:13:27 PM »

Hi,
A4 B7 BFB 1.8T, hardware modification: hybrid K03 turbine, FMIC, 430cc injectors, metal tip, 200cpsi cat. Air filter and maf are stock.

I've already made a lot of remaping to tune my car equipped with 8E0909518AQ 0020 ecu.
IOP/IRL taken from BAM and rescaled all other maps to changed rl_w axis (my ecu was scaled only to 145 load)
I'm running "feed forward" control for boost controler described at forum.

But I do NOT touch antyhing related to maf.

What is my problem? S4 wiki says:"Another good MLFHFM sanity check is to log ps_w vs actual boost at WOT - ps_w should generally be slightly below actual boost"

As you can see in my log ps_w is lot higher than pvdks_w and because of that rl_w is higher than rlsol_w. (I checked and there is no leakage at inlet)

It is normal, or should I change something?
Now at WOT I feel something like torqe intervention, but I can't prove it, because i don't have all variables in ME7logger for ME7.5.

Thanks for answers.
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prj
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« Reply #1 on: December 11, 2024, 03:31:19 PM »

ps_w is modeled pressure from VE model.

Of course it's completely wrong when you changed turbo and exhaust.
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damianalex
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A4 B7 1.8T 8E0909518AQ 0020


« Reply #2 on: Yesterday at 12:00:50 AM »

I found old topic with similar problem I guess...
 http://nefariousmotorsports.com/forum/index.php?topic=13929

Your VE model (pressure to load conversion) is not right because ECU is requesting too much boost to reach target load.
VE model is adjusted by:
KFURL - base
KFPBRK/KFPBRKNW - multiplicative correction
KFPRG - additive correction

Which one to change I can't tell you based on the data you have - you need to check on part throttle also how it is behaving.
If you have the problem in the entire range, then KFURL will help, if it's only on high boost then KFPBRK/NW should be changed at higher load.

So I'll try make logs covering wide range of load and with that I will adjust maps mentioned above.

Thanks a lot prj.
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prj
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« Reply #3 on: Yesterday at 03:13:17 AM »

Before adjusting pressure test the complete intake from turbo inlet.
If you have a small leak in something connected to the manifold it will also show up in a similar way.
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nyet
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« Reply #4 on: Yesterday at 10:24:57 AM »

ps_w is modeled pressure from VE model.

Of course it's completely wrong when you changed turbo and exhaust.

Is that enough to account for the difference?
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ME7.1 tuning guide
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Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
prj
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« Reply #5 on: Yesterday at 02:11:05 PM »

Is that enough to account for the difference?

The biggest difference is the turbo hotside/turbine being bigger.
That affects VE in a massive way at higher boost levels. At lower boost the difference is very small, but as you go higher it starts to become larger and larger, as the OEM hotside/turbine wheel would be creating massive backpressure at those levels, that just isn't there with the upgraded turbo.

But as I wrote before, if there's a small boost leak it'll show up the same way.
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damianalex
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A4 B7 1.8T 8E0909518AQ 0020


« Reply #6 on: Yesterday at 02:59:10 PM »

I've looked through my logs and I can confirm that difference is only on high load, so as usually prj has right Smiley

I was rebuilding my engine this year and after that I checked for leaks, but to be sure I will do double check before adjusting VE model.
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