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Author Topic: Boost falling off, what am I missing here?  (Read 13661 times)
NOTORIOUS VR
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« on: November 03, 2011, 08:45:11 AM »

Alright, so I've been playing with a K04 car recently, and I keep getting this boost drop every time no matter what gear around 5300rpm... like clock work... no codes, no limits that I can see, holds boost just fine before that... WGDC is still going up just as it should... no TC, load just falls off.

I just don't get it... looking for suggestions.

Attached are the logs.

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judeisnotobscure
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« Reply #1 on: November 03, 2011, 11:37:51 AM »

what do the egt's say at this point in the pull?
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I have a b5 s4
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NOTORIOUS VR
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« Reply #2 on: November 03, 2011, 11:46:56 AM »

EGT's are disabled as they are dead...

The boost_drop.xls is the full plotted log... I just didn't bother to host it up here..
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Rick
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« Reply #3 on: November 03, 2011, 12:02:49 PM »

It almost looks like a collapsing intake hose.
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NOTORIOUS VR
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« Reply #4 on: November 03, 2011, 12:35:23 PM »

I too have a hard time believing this is a software issue.. there is nothing in the logs that suggests that it is.

I've thought maybe bad N75, bad DV's... haven't thought about something on the intake side though...
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Jack_Snows
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« Reply #5 on: November 03, 2011, 05:18:32 PM »

what car is this on?
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Gonzo
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« Reply #6 on: November 03, 2011, 05:22:39 PM »

Monitor fueling, EGT and TP position.
Could be that ME7 is closing the TP on you.
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judeisnotobscure
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« Reply #7 on: November 03, 2011, 05:24:58 PM »

i think i'm getting on the intake path blockage bandwagon here.
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I have a b5 s4
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NOTORIOUS VR
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« Reply #8 on: November 03, 2011, 08:27:02 PM »

Monitor fueling, EGT and TP position.
Could be that ME7 is closing the TP on you.

I take it you didn't look at the logs...
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Gonzo
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« Reply #9 on: November 03, 2011, 08:30:31 PM »

Monitor fueling, EGT and TP position.
Could be that ME7 is closing the TP on you.

I take it you didn't look at the logs...
Nah I just looked at the pretty images and missed the fact that you had actual logs on there.
Sorry man I'll take a look later.

I've had this issue before where ECU will throw fault and will 'request' boost but it doesnt actually open/close the wastegate, but your issue sounds like a hardware issue fo' sho'.
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NOTORIOUS VR
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« Reply #10 on: November 03, 2011, 08:37:03 PM »

you mean, the ECU was requesting boost but wasn't actually raising the DC on the N75? 

I can see that happening I guess... in this case the WGDC is still slightly rising (from mid 70's to ~81% which his pretty much exactly what I have in the WGDC table.

Next time I see the car I will look into the hardware side of things a little more.

Thanks for all the suggestions guys, I'll report back when I have some time to tinker and look into it more.
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Jack_Snows
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« Reply #11 on: November 04, 2011, 05:00:56 AM »

what car is this on?

If its an MED9.1 platform the ECU will protect the engine by minimizing boost. There are several conditions it does this for. The most common being FRP not being met.
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NOTORIOUS VR
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« Reply #12 on: November 04, 2011, 06:28:48 AM »

sorry it's a B5 S4 so ME7
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kenmac
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« Reply #13 on: November 06, 2011, 10:22:50 PM »

Really looks like a collapsing TIP under heavy vacuum.  Mount a camera and light under your hood focused on the TIP and go for a drive.  Cheesy Grin
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Giannis
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« Reply #14 on: November 21, 2011, 03:20:51 AM »

Is this car with manual or automatic transmition?
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