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Author Topic: My cause of no boost?  (Read 3029 times)

Offline Big Tone

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My cause of no boost?
« on: 20 June 2010, 13:50 »
Right, I think I have cracked it!

I have been seeing 0.35 Bar(5psi) actual boost and 2bar (14.5 psi) requested boost on vagcom when logging and would like opinions before I fork out for a part. (NO FAULT CODES WHEN SCANNING)
Checks:
Pressure test - fine ( one very small leak found and remedied)
Wastegate actuator - can be moved by hand (It is fairly stiff (spring compression?) but has smooth movement)
DV - Fairly new Forge007p - yellow spring
N249 is bypassed
Problems:
Hissing on accelleration

Cause?
I presume that the N75 is shot, therefore not controlling the wastegate and allowing air to escape as soon as 5psi is seen, resulting is the actual boost seen.

What do ya think?
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Offline Big Tone

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Re: My cause of no boost?
« Reply #1 on: 20 June 2010, 19:17 »
I have read that you can test this valve by blowing into the two shorter ports and NO air should pass throught the valve and out of the longer port. Is this true?

If not how can you test it?
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jamie16v

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Re: My cause of no boost?
« Reply #2 on: 20 June 2010, 19:50 »
Quote from: Big Tone on 20 June 2010, 13:50
Right, I think I have cracked it!

I have been seeing 0.35 Bar(5psi) actual boost and 2bar (14.5 psi) requested boost on vagcom when logging and would like opinions before I fork out for a part. (NO FAULT CODES WHEN SCANNING)
Checks:
Pressure test - fine ( one very small leak found and remedied)
Wastegate actuator - can be moved by hand (It is fairly stiff (spring compression?) but has smooth movement)
DV - Fairly new Forge007p - yellow spring
N249 is bypassed
Problems:
Hissing on accelleration


i am having very simular symptomns to you but i am seeing about 14-16 psi peak and around 12-13psi avearage..
i am getting the hissing too and its been bugging me. will have to do another boost leak test to investigate where it is coming from.. :undecided:
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Offline Big Tone

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Re: My cause of no boost?
« Reply #3 on: 20 June 2010, 20:06 »
From the research I have done I understand that if the N75 is fooked, the wastegate will be opening at 5psi, venting the rest to atmosphere, don't know whether you would see anything more than 5psi - but I am no expert.
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Offline Wazzzer

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Re: My cause of no boost?
« Reply #4 on: 20 June 2010, 20:13 »
yeah that sounds about right, you got a mate with a Golf you could borrow one from?
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Offline Big Tone

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Re: My cause of no boost?
« Reply #5 on: 20 June 2010, 21:03 »
Unfortunately I don't, thinkin bout just buyin new, tried to test using output test on vagcom, thought I'd check before I removed the valve, worked fine and now it comes up with error/function not avaliable when I try  :cry:

When I blow air through the charge side, it comes out of the wastegate port and nothing comes through when I try through the TIP side. did notice however that after testing output on vagcom i was able to blow air through the tip side for a short while, which makes me think it is taking longer to close - sticking when in use.

I would just like to be 100% before shelling out for a new one.
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Offline Wazzzer

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Re: My cause of no boost?
« Reply #6 on: 20 June 2010, 21:31 »
you going to Inters? You'd be welcome to borrow mine for a test if you do, it's only a few months old
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Offline Big Tone

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Re: My cause of no boost?
« Reply #7 on: 21 June 2010, 12:55 »
Nice one, but unfortunately I'm not, working 12hr days, one day off a fortnight for the forseeable future :cry:

Going to pick a new one up from VW on Friday lunchtime so fingers crossed it will sort it, don't know what else it could be.

Nice one anyway, much appreciated
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Offline Hulmie

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Re: My cause of no boost?
« Reply #8 on: 21 June 2010, 13:39 »
just a query, you say its been showing 2bar (14.5 psi) requested boost on vagcom when logging, however 2bar is not equal to 14.5psi.

Im sure 1bar is about 14psi and 2bar is 28psi. maybe just a typo error
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Offline Big Tone

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Re: My cause of no boost?
« Reply #9 on: 21 June 2010, 21:12 »
Taking into account atmospheric pressure bud, @ 1000mbA, requested boost showing 2000mbA, therefore 1000mb "actual" boost pressure, equal to 14.7psi.
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