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Author Topic: "low" Mass Air Flow @ High RPM With Stock & Tuned File  (Read 22043 times)
!nfern0
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« on: April 26, 2015, 02:33:03 AM »

Hi Guys,

I've compared my Tune with some other 1.8t... It seems that my enginge is struggling at higher RPM with mass air flow.

I get about 165g/s maximum mass air flow with stock AND tuned file. I've seen up to 250g/s mass air flow at other 1.8t engines...

So there must be a hardware problem, but I don't know what... Maybe you can help me.

Today i checked the cats and it looks fine to me, they are not clogged. What should i check next? N75? Air Filter?

Attached log files of a Stock and a tuned WOT-run.

Many thanks in advance.
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!nfern0
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« Reply #1 on: April 26, 2015, 02:40:46 AM »

Here the files...
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nyet
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« Reply #2 on: April 26, 2015, 11:58:57 AM »

Make sure your inlet isn't collapsing
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!nfern0
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« Reply #3 on: July 10, 2015, 06:48:23 AM »

Hey there!

I'm still struggling with this issue...

What I did so far:

1. spent some money on new ccv hoses underneath the intake manifold. one of them was broken.

It was the one between the manifold and the one-way valve. So i lost some boost there.
Now the engine has about 0,2 bar (3 psi) more pressure around Pmax. Second effect was, that i "lost" some mass air flow -> delta of about 10g/s.
This makes sense so far, the MAF Sensor is reading now a little less, because the air isn't escaping through this hose.
If I do a leak test up to 2,5 bar (36 psi) there is no fluctuation of air. The air is slowly blowing by the pistons. You can hear it, if you take out the dipstick for the oil. I put on pressure at the first hose after the pressure pipe. So it still could be, that i lose some air between charger and this spot (hose to dv or to n75). I tried to check this both hoses by dismounting them and do a pressure check. They also seem to be ok.


2. bought a new DV and installed it. I heard some strange noise when the charger was boosting. thought the membrane could be torn. the noise is still there sometimes...

One thing with the DV which I don't understand completely: The charge pressure is "controlling" the DV? So for example, if the engine has 1 bar (14 psi) boost pressure, this pressure is "closing" the DV? This 1 bar is on the little pipe on the top of the DV to hold it closed? So what is this N249 for? Maybe there is something broken and the pressure is not closing the DV correctly?
If YES, this could be an explanation for the low mass air flow? It wold be an open circuit from "after charger" to "front of charger".

3. installed a gopro to see if the inlet is collapsing at WOT.

There was no collapsing visible. I ended up buying the SAMCO inlet hose. Still no effect. Same MAF as before.

4. new air filter and removing the inlet before the airbox.

no effect.


Attached i have an actual log. There you can see the still low mass air flow, although the engine should be able to do ~200g/s. The second issue is that the actual boost pressure at high rpm is also really low. This issues are the same with stock software! I'm pretty sure it's still a hardware problem.

Do some of you have some ideas? Maybe the MAF Sensor is broken? The values below 3000 rpm seem to be ok if I compare it to other 1.8t BAM engines. If I buy a new MAF-Sensor it wouldn't solve the problem with the "low" boost at high rpm?

one more thing for information the idle is a bit oscilating...

Thanks in advance.
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!nfern0
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« Reply #4 on: July 10, 2015, 07:02:27 AM »

log...
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spacey3
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« Reply #5 on: July 10, 2015, 08:38:54 AM »

What turbo do you have?
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!nfern0
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« Reply #6 on: July 10, 2015, 09:20:45 AM »

stock! k04-23
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spacey3
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« Reply #7 on: July 10, 2015, 09:44:12 AM »

For the boost, weak actuator? I had issues with mine and had to change it.

Maf readings... I guess try a new maf, they tend to under read when they die don't they?
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nyet
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« Reply #8 on: July 10, 2015, 10:12:05 AM »

Looks fine to me. Turbos are struggling to keep up, could be going out. Might need to increase Ilimit until your req meets actual, but odds are that is 95% dc.

Also, you should be logging ps_w
« Last Edit: July 10, 2015, 10:13:48 AM by nyet » Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

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 experience.
!nfern0
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« Reply #9 on: July 10, 2015, 10:14:46 AM »

I checked the actuator by applying negative positive pressure with a syringe... it held it's position for more than five minutes...

The WGDC looks also fine to me if i compare it to similar engines. until rpms > than 3500 rpms... it looks like there is a bottleneck somewhere (for me). (intake or exhaus system)

consequences of this bottleneck is stagnating mass air flow --> and the effect of this is low boost, since the turbine is not getting enough exhaust mass air flow.

I also calculated mass air flow with the AFR values and the injector on time... it also seems to fit that the maf readings are right...

this above is all just thinking! maybe I'm wrong...
« Last Edit: July 13, 2015, 10:24:14 AM by !nfern0 » Logged
!nfern0
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« Reply #10 on: July 10, 2015, 10:16:39 AM »

Looks fine to me. Turbos are struggling to keep up, could be going out. Might need to increase Ilimit until your req meets actual, but odds are that is 95% dc.

Also, you should be logging ps_w

I tried to increase I Limit so that i had 95% WGDC above 4500 rpm all the time... no difference in boost!
Like i said, i think it's not enough exhaust mass flow through the turbine...

next time i will log ps_w
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nyet
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« Reply #11 on: July 10, 2015, 10:17:10 AM »

I tried to increase I Limit so that i had 95% WGDC above 4500 rpm all the time... no difference in boost!
Like i said, i think it's not enough exhaust mass flow through the turbine...

next time i will log ps_w

That means your turbo is done or your wg is leaking
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ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

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 experience.
coreyj03
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« Reply #12 on: July 13, 2015, 07:14:24 AM »

That means your turbo is done or your wg is leaking

he is most likely correct. i have ran into a leaking wastegate a few times before on 1.8t, very difficult at times to diagnose.   pull the downpipe off and feel the wastegate flap. If it can rotate or move about then either adjust your wastegate preload or replace the turbo.
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!nfern0
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« Reply #13 on: July 16, 2015, 09:52:15 AM »

i will take a look at the wg when I find time...

Today I did a log with ps_w.

msdk is oscillating really weird above 4000 rpm... hardware wasn't touched.
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!nfern0
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« Reply #14 on: August 01, 2015, 09:03:29 AM »

Hi again!

Today i did some logging with disconnected (electrically) N75. I've read, that the boost pressure should be ~0.5...0.6 bar (~8...9 PSI) with k04-23.
Can someone confirm this values?

Take a look at the log and the screenshot. The boost is about 0.3 bar (5.5 PSI).

Yesterday i dismounted the downpipe and had a look at the turbine-wheel ant the wastegate. Looks pretty fine to me!

@ spacey3: it seems that the actuator is really weak. the membrane seems to be ok (it holds its position). But the spring seems to be to weak...

Is it a good idea to increase the spring preload? Has someone experience with that? Otherwise the best idea would be to buy a new actuator...
« Last Edit: August 01, 2015, 09:19:49 AM by !nfern0 » Logged
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