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Thread: lean on boost

  1. #1
    jay1601's Avatar
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    lean on boost

    on light throttle and idel runs perfect between 14.6-15.1

    on boost (anything over 4PSI) will drop straight to 10.0 (lowest the gauge will go)

    i've got a "stage 1 remap" which will be a generic map

    would it be worth spending money on getting a custom map done to make it run correct or just wait until i fit my K03S on then get a custom stage 2 map
    Audi A3 8L 1.8T breaking.
    front bumper, impact bar, slam panel, full engine and loom sold.
    everything else for sale.

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  3. #2
    beachbuggy's Avatar
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    Faulty fpr could be the cause.

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    jay1601's Avatar
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    if i'm going to replace it would it be worth sticking a 4 bar one in for future mods or just replace with another 3 bar
    Audi A3 8L 1.8T breaking.
    front bumper, impact bar, slam panel, full engine and loom sold.
    everything else for sale.

  5. #4
    "Stick a V8 in it!"

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    Is this a proper wideband guage?

    10.0 is rich, not lean.

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  6. #5
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    10:1 isn't lean mate, it's VERY rich! ideally you want mid 12's I'd think. I'd imagine something will be a miss somewhere. more than likely a boost leak. it'll be seeing the air coming in through the MAF, and fuelling for it accordingly, so when some of the air escapes, you end up with too much fuel.

    Have you checked the fuel trims?
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  7. #6
    jay1601's Avatar
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    AEM Uego.

    i haven't got vag-com outside work

    might take a look for vac/boost leaks over xmas time off. see if i can find anything
    Audi A3 8L 1.8T breaking.
    front bumper, impact bar, slam panel, full engine and loom sold.
    everything else for sale.

  8. #7
    camscockle20vT's Avatar
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    How easy is the fpr to change? Any linkys people

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    jay1601's Avatar
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    pull the U clip out (don't know the proper name for it) then just prise it out. easy 2 min job
    Audi A3 8L 1.8T breaking.
    front bumper, impact bar, slam panel, full engine and loom sold.
    everything else for sale.

  10. #9
    RIP S3dave

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    14.7 AFR Lambda 1

    Leaner is higher than 14.7
    richer is lower than 14.7

    Usual zone to aim for is in the 12's under boost, not 11's or 10's
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  11. #10
    Chlippo's Avatar
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    does vag shows any faults for a faulty fpr? my car is running lean (14's all the time, boost or no boost)
    are there any upgrades or just replace with oem?
    Audi S3 AMK
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    For help/info/pricing on xs manifold and downpipe pm me (not affiliated, nor a reseller trader, just an enthusiast!)

  12. #11
    <tuffty/>'s Avatar
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    Quote Originally Posted by Chlippo View Post
    does vag shows any faults for a faulty fpr? my car is running lean (14's all the time, boost or no boost)
    are there any upgrades or just replace with oem?
    There is no fault code for the FPR as its not electrical and therefore not tied into a module of any kind that can monitor its state... however there are tell tale signs which can be logged through VCDS and of course a pressure gauge

    Should be mentioned that it is rare for an FPR to go faulty... only FPR related issues I have seen has been from BAM engine code S3's when bits of rubber from the fuel pipes have collected in the fuel bowl around the FPR blocking it off but that gives different symptoms... in situations like this is is more likely the fuel pump thats at fault as it gets tired and cannot deliver the required fuel pressure under boost... as boost goes up so does the FPR's rating (3bar + boost pressure) and the harder the pump has to work... a tired pump won't be able to keep up and therefore goes lean under boost...

    The easiest way to diagnose fuel pressure issues is to just fit a fuel pressure gauge in the fuel line and see if the pressure rises at the same rate as boost... should be around 3 bar (on a 3 bar FPR) on idle rising to whatever your peak boost is (if 1.2bar then you will see around 4.2bar)... if you don't see that then its likely the pump is the culprit...

    On a wideband ECU (AMK/BAM/AUM) you can check blocks 001 and 031 and you will see lambda adjust in 001 go mental trying to add fuel and the actual lambda in block 031 start to go into leaner figures despite the request being whatever it is... checking block 032 will show if there is a large positive figure in the long term fuel trim too

    Chilippo... in your case (as I remember you posting about this before) having 14's across the board sounds more like thats what the map is asking for... logging block 031 in VCDS will show you this... 14's sounds like std fuelling and IIRC you have had yours mapped and not logged... logging block 031 will show you what your fuellign is doing... if the request is 14's and the actual is 14's then the only problem you have is your remap... if the request is mid 12's and the actual is 14's then maybe you have an issue

    <tuffty
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  13. #12
    RIP S3dave

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    Quote Originally Posted by Chlippo View Post
    does vag shows any faults for a faulty fpr? my car is running lean (14's all the time, boost or no boost)
    are there any upgrades or just replace with oem?
    as Previously said.....
    log block 031 and confirm what the MAP Is REQUESTING
    If dimsport, then their "lambda" map aint correct.... and does diddly squat
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  14. #13
    Chlippo's Avatar
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    Thanks tuffty. Bill proposed to log those (and i will) but for my own curiosity and knowledge your explanation was needed.
    I will get a proper vag next time i work on the car.
    Audi S3 AMK
    Relentless-Manifold, Relentless-3" downpipe decat, Forge 007 DV, autobahn88 TIP, K&N Panel filter, EBC yellowstuff brake pads, R32 ARB, Custom column dual gauge pod...waiting for a remap!

    For help/info/pricing on xs manifold and downpipe pm me (not affiliated, nor a reseller trader, just an enthusiast!)

 

 

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