s3 8L - stage 3 - Boost drop at 6000rpm

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Topic: s3 8L - stage 3 - Boost drop at 6000rpm (Read 8718 times)

madswp

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	s3 8L - stage 3 - Boost drop at 6000rpm « on: March 19, 2015, 01:32:23 PM »

Hello Nefmoto's Wink

long time since i messed around with me7 ecu's. but now i have a problem:

Car specs:
audi s3 8L 225hp BAM engine.
upgraded h-beam conrods,
siemens deka 630 ml injectors
stock pistons with 9.0:1 CR
garrett gt3071R A/R 0.64

Car runs great up to 6000rpm then boost drops from ~2500mbar to ~1600mbar. this is happening on every run i take and doesn't matter how much load i apply (3-4-5 gear, all the same at 6000rpm)
EGT reaches max 850c, Lambda ~0.82. ignition retard ~3degrees.
adjusting WGDC at KFLDRL makes absolutely no differences. i can control boost fine under 6000rpm, but over it does always drop.
i have tried finetuning several LDR based maps (even locking KFLDRL up to 95%), but makes no differences. as you can see on attached log, then the boost is really quickly dropping.
could a maxed out MAF sensor cause this behavior? it reaches 4.88V on signal line.
wastegate cracking pressure is set to 0.7bar.
i am really starting to think it might be a hardware problem, maybe wastegate gets blown open by exhaust pressure.

what are your thoughts on this?

Regards


« Last Edit: March 19, 2015, 01:36:57 PM by madswp »	Logged

prj

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #1 on: March 19, 2015, 02:21:49 PM »

Can you show a photo of your intake setup? Filter to turbo?
It is probably collapsing.


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fredrik_a

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #2 on: March 20, 2015, 02:48:26 AM »

I usually fit a pressure gauge fitting after the air filter for calibration purposes. If it starts to read pressure levels below normal atmospheric pressure, the air filter can not flow enough.


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prj

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #3 on: March 20, 2015, 06:09:25 AM »

Quote from: fredrik_a on March 20, 2015, 02:48:26 AM

I usually fit a pressure gauge fitting after the air filter for calibration purposes. If it starts to read pressure levels below normal atmospheric pressure, the air filter can not flow enough.

That's not quite right, most filters have a small pressure drop from what I have tested.
And if you have a big soft silicone hose, then even 0.1 bar of "negative boost" can collapse it.

@OP, check your intake, make sure you are not using any loose silicone hose. Do a run without the air filter and see if without the air filter the problem goes away (just dont drive around like that).
If you have a dyno, you can visually confirm it.


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janne

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #4 on: March 23, 2015, 03:52:40 AM »

Can be stupid idea, but look KFMDBGRG


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madswp

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #5 on: March 25, 2015, 12:04:40 PM »

Thank you for your replies! Wink

It was the stock air filter case which was the problem like PRJ said. It did colapse the intake hoses between turbo and filter.

btw. can't recommend samco sport hoses for intake. They are very soft compared to other types i have tried, (know filter and box was the issue here, but anyway)

Mads


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prj

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #6 on: March 25, 2015, 12:11:37 PM »

Problem solved then.


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aef

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #7 on: March 26, 2015, 12:23:10 AM »

Im interested in Results with the gt30 with 9:1cr


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fredrik_a

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #8 on: March 26, 2015, 03:57:55 AM »

What is the real maximum boost pressure? It seems to be beyond the limit of the MAP-sensor (4.600-5.600 rpms) at least, or is it insanely well calibrated for 1.55 bars of boost


« Last Edit: March 26, 2015, 03:59:43 AM by fredrik_a »	Logged

madswp

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #9 on: March 26, 2015, 01:27:03 PM »

the car is absolutely stock right now besides conrods, turbo and fuel system. i did play a little on dyno and pushing it to the edge. it did 352hp@5700rpm and 470nm. but with a lot backpressure in exhaust (over 1.5bar on stock exhaust after cat) and i am also guessing the intake could be better (stock airfilter and modded box). the boost is dropping down to ~1.3 bar at 7000rpm.
max boost was locked by KFLDRL to 1.6bar, so close to 1.55.

right now it got 319hp at 6500rpm. at 2.050mbar absolute on octane 95 and ignition between 16-19 degrees at higher rpm . i think thats a little more sane with that setup Wink

the tuning continues.....


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madswp

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #10 on: March 26, 2015, 01:36:12 PM »

btw another question:

why does the engine run VERY BAD without airfilter? it cant rev at all and feel like its cutting ignition when driving. is that normal on ME7 or is it just something thats needs to be calibrated?


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nyet

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	Re: s3 8L - stage 3 - Boost drop at 6000rpm « Reply #11 on: March 26, 2015, 06:07:52 PM »

Quote from: madswp on March 26, 2015, 01:36:12 PM

The MAF requires a reasonable air column.

Full airbox is the best. Anything else, forget it, you'll be fighting fuel trims until the end of time.


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