Author Topic: BPY FSI P2177 CEL - Boost leak - Vacuum Leak - Bad Economy Etc  (Read 616 times)

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superchicken

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I'm trying to track down a potential boost or vacuum leak.

Engine is a 2007 BPY 2.0T with DSG.

I replaced the intercooler last year with a Golf R unit and greased/checked all the pipes to/from the intercooler then.

Replaced the DV with the upgraded unit then as well.

Car is averaging 11/100 on the highway in cruise at 100-110kph flat roads. 

I can hear trumpeting through the CTS intake.

Car throws P2177 code which seems to be a vacuum leak.

Car idles smooth and drives fine, but under part throttle cruise/accel it slowly increases and decreases boost (you can feel a mild surging).

Boost requested / actual seem to be fine.

Anyone know what the diameter of the turbo inlet is so I can make a boost leak test cap?  (I'm too lazy to pull it all apart just to measure).
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Autohau5

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What are your fuel trims in 01-08-32-1/2 ? What does a log of MAF (01-08-02-4) look like during a third gear pull from 2000rpm to 5000rpm? Should be a pretty linear increase with very little to no noise.
'01 A6 2.7TT 6MT  |  '81 Rabbit S 16VG60   |  '16 Golf .:R    |    '04 Touareg V10 TDI    |   '96 YZF750R

superchicken

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I'll check those.  I'm using obveleven instead of vag-com so I'll have to check what block channel the fuel trims are in.
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superchicken

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Group 32
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superchicken

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Trims at 110kph cruise flat ish highway - -2.5% and 22.3%

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superchicken

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Lambda on a highway pull - -3% and 0.75V
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83RedRoc

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group 32 ( or block 32 on VCDS )  is idle long term and partial long term,

So you saying that your partial long term is +22%?  If so, it's having to add 22% more fuel on top of base just to try and maintain the requested AFR.   These will reset every time you clear DTC's.  At 25% I belive that it throws a code.

Could be a bad MAF, and this car is particularly sensitive to intakes, the stock housing isn't round, and the sensor is calibrated specifically for the shape it was from the factory.   
« Last Edit: May 27, 18, 09:34 by 83RedRoc »

superchicken

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Here's a chart of a 4th gear pull.  You can see the boost oscillation as well.  80g/s seems way too low for a MAF at nearly full throttle, no?

https://docs.google.com/spreadsheets/d/1sLWWiPelNSWazj2yYmmmuvrIBZPCKjnD5kAskOAh_is/edit?usp=sharing
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superchicken

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superchicken

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I should mention the boost oscillation existed prior to installing the CTS intake.
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83RedRoc

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80g/s is wayyyyy too low.   Should be up around 200 if you are on a stock tune.   Your MAF is probably pooched.

The logs are weird.   I've never seen a request so low, maybe just something to do with it not being VCDS.


superchicken

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Yeah I figured as such, something about being .8 of your BHP in g/s
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83RedRoc

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yup.  g/s / .8 = rough hp number.   This isn't set in stone, but I'm hoping you are making more than 100hp !

But that's why your fuel trim is so far out of whack.   MAF see's no air, so if it was controlling it you'd be crazy lean, 02 sensor is adjusting, to compensate but if you are at 25% its reached its maximum value meaning the ecu could still be running a leaner mixture than it wants, it simply has no more room to adjust it.


Autohau5

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Good sleuthing!!
'01 A6 2.7TT 6MT  |  '81 Rabbit S 16VG60   |  '16 Golf .:R    |    '04 Touareg V10 TDI    |   '96 YZF750R

superchicken

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I'll have to see if anyone in town has a spare mag I can try swapping and I'll clean mine as well. Nic?
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superchicken

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Cleaned the MAF with a spray and the readings went up to 170-180g/s under full throttle pulls.  Wife reports the fuel econ on the last tank was 8L/100km avg.
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Autohau5

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Good job. Iíll submit my invoice shortly.
'01 A6 2.7TT 6MT  |  '81 Rabbit S 16VG60   |  '16 Golf .:R    |    '04 Touareg V10 TDI    |   '96 YZF750R

superchicken

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Car still surges a bit on boost.  Invoice denied!!!
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superchicken

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I'm back, more charts.   The boost oscillation is well defined on partial load acceleration.  https://docs.google.com/spreadsheets/d/1ns7YBznbiuxextpEuzhFI_6uaQGpEsP6YVpKvCV15EM/edit?usp=sharing  Is the boost spike on initial demand normal for a GTI or should i be looking at my wastegate / N75?
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superchicken

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