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  1. #1
    s3_kev's Avatar
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    Boost loss help!!!!

    i recently had an AMD stage 2 remap which has increased boost to 25psi, all has been fine up untill friday now its only peaking at 20psi but its still holding the boost higher like it did with the increased boost it just dosent seem to spool up anywear near as quick as it did,
    i have done a boost leak check and its holding plenty of pressure, i have changed back to std n75 valve, changed the forge dv over to std tried unplgging maf, i have already by passed the n249 valve so doubt its that also tried unplugging and no difference, done a run using vag.com and the maf is doing 180 ish which i think is normal?

    so im beggining to wounder if the turbo's now nackered, anyone got any other sugestions for me to check otherwise its either a trip to AMD for them to diagnose which i dont really want to do as im a mechanic and can check everything myself if i no what to check,

    cheers

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  3. #2
    S3 Paul's Avatar
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    I know its not an easy job... but the turbo exhaust housing and or the manifold maybe cracked...
    I had this happen not long after i bought my car.
    It was beggered. cracks everywhere and one across the waste gate. which ment it would never seal.
    Noggy Blue 2001 S3

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  4. #3
    s3_kev's Avatar
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    i took the turbo outlet pipe from turbo to charge pipe off earlier to see if that had split etc and whilst it was off i had a look at the manifold but could only really see the top half but might takeit back off again and use a mirror to have a good look if nec, did you have power/boost loss with the cracks to then??

  5. #4
    Dani_B19's Avatar
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    MAF readings are low for a stage 2 kev, should be around 220 g/s iirc!
    Driving the most secretive S3 on ASN

  6. #5
    s3_kev's Avatar
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    sorry for all the deleted posts was trying to upload my vag.com logs but cant seem to figure it out, anyone no how to do it?

    cheers for that dani ill look into the maf dont really want to buy one unless it definantly that though as there are alot of people who buy all these things and find out its not the cause,

  7. #6
    Dani_B19's Avatar
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    No worries pal, i know my MAF's knackered just want to get it vag-com'd to see how bad it is.
    Driving the most secretive S3 on ASN

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    Yeh maf readings are quite low. 180g/s would be about 225bhp. So standard.

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  9. #8
    S3 Paul's Avatar
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    Ye i had a boost problem with my turbo housing being cracked.

    It wouldnt peak as high as it should,

    Im not realy sure about your MAF readings. Surely AMD would tell you what they expect to see with your map?
    Email your logs to them... Ive done it before with JBS. the y will probs see the problem with the readings.
    Noggy Blue 2001 S3

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  10. #9
    s3_kev's Avatar
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    Quote Originally Posted by S3 Paul View Post
    Ye i had a boost problem with my turbo housing being cracked.

    It wouldnt peak as high as it should,

    Im not realy sure about your MAF readings. Surely AMD would tell you what they expect to see with your map?
    Email your logs to them... Ive done it before with JBS. the y will probs see the problem with the readings.
    i rang AMD yesterday and spoke to some guy who told me that the maf wouldnt cause boost loss and with out looking he couldnt tell me what the maf readings should be, dont think he was to clued up tbh

  11. #10
    Westy's Avatar
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    The maf wont cause boost loss but will cause poor running of the car. My stage 1 (254bhp) gives a maf reading of 201 so your reading is very low and is obviously a symptom of whatever your overall issue is. Are you able to test the wastegate to make sure its holding 25psi ok?
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  12. #11
    s3_kev's Avatar
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    Quote Originally Posted by Westle View Post
    The maf wont cause boost loss but will cause poor running of the car. My stage 1 (254bhp) gives a maf reading of 201 so your reading is very low and is obviously a symptom of whatever your overall issue is. Are you able to test the wastegate to make sure its holding 25psi ok?
    how would you check if the wastgates holding the pressure?? cheers

  13. #12
    s3_kev's Avatar
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    SORTED!! but im a bit unsure what was wroung lol,

    went out to the car and removed the tip from the turbo to check if turbo was ok, all felt ok only a small bit of play in the bearing and no oil from what i could see then pulled the actuator out to make sure it wasnt sticking etc, followed the vac line up from actuator to n75 to check for splits (however i belive splits would give over boost issues) after that i checked the conection at the map sensor all was good again,
    then i disconected the battery to reset the ecu reconected after 5-10 mins,
    let the car warm up then went for a drive back onto full boost at 25psi and the turbo is kicking in alot quick and harder i havent done a vag.com check on the mass airflow yet as need my mate for his laptop but full power is back,

    so i guess it was either a sticky actuator which i doubt or a glitch in the ecu due to a possible over boost issue which then went into soft limp mode, which clearing codes wouldnt remove,

    all in all im happy again but im concerned as to weather it will happen again, could it be due to the n75j fitted even though AMD were told it had the n75j fitted at the time of the map?? if it happens again i will remove the n75j and try the std one again hopefully the fault wont return,

    cheers to all for the help and input

  14. #13
    fran-s3's Avatar
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    when I had a n75j valve fitted that happened to me when it would limp out and not come back for days... I'm remapped, went back to standard n75.

  15. #14
    Westy's Avatar
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    Quote Originally Posted by fran-s3 View Post
    when I had a n75j valve fitted that happened to me when it would limp out and not come back for days... I'm remapped, went back to standard n75.
    yeah could well be the N75 valve, do you have a BAM engine code Kev?
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  16. #15
    s3_kev's Avatar
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    Quote Originally Posted by Westle View Post
    yeah could well be the N75 valve, do you have a BAM engine code Kev?
    no mate i have an APY

    i have been running the n75j for some time tough but was with my custom code phase1, i also rang AMD today who said it would have been mapped with the n75j he told me to contact them if it does it again,
    i also fitted the std n75 to see how much difference it makes and the boost tails off loads when thats fitted so im back to the n75j just have to see what happens i guess, might get an n75h to try if it does happen again

  17. #16
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    I was under the impression you couldnt map a car with the n75j, thought you had to have the car mapped with the standard n75 then put the n75j after the map!
    Driving the most secretive S3 on ASN

  18. #17
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    APS who really know there stuff advised me never to put an n75j valve on my car for the exact same reasons! Sure it boosted more aggresively when it was working but I found the boost died of to early for me with it - feels more prolonged with the standard n75. Mine an AMK by the way. Swings and roundabouts mate.

  19. #18
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    ok have found the problem its the coolant temp sensor, replaced and now have fill boost using less fuel and the car drives so much smoother think the sensor has been on the blink for a few weeks with out noticeing o put the excess use of fuel down to the remapp, i also ended up buyong a new maf sensor which arrived today so i need to do some vag.com logs on the old maf and new maf to see if the new ones needed, probably do that by the weekend

  20. #19
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    ok i thought id fixed this issue but appears not, so in total i have now replaced n249 valve i did have it bypassed but still changed it and put back into series, also changed maf and coolant temp sensor, i also swapped the n75j out in favour of the standard n75 this was the longest lasting fix so far but then the other day its dropped boost back off to 20psi,
    so i have hardly any sensors to try now either the mapp has killed the stanard n75 as it may have done to the n75j??
    also i had a lamba sensor code the other week, could a lamba sensor cause boost loss?? im really beginig to have enough of finding this problem now so any help advise would be good cheers

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    Quote Originally Posted by s3_kev View Post
    ok i thought id fixed this issue but appears not, so in total i have now replaced n249 valve i did have it bypassed but still changed it and put back into series, also changed maf and coolant temp sensor, i also swapped the n75j out in favour of the standard n75 this was the longest lasting fix so far but then the other day its dropped boost back off to 20psi,
    so i have hardly any sensors to try now either the mapp has killed the stanard n75 as it may have done to the n75j??
    also i had a lamba sensor code the other week, could a lamba sensor cause boost loss?? im really beginig to have enough of finding this problem now so any help advise would be good cheers
    I would of thought the lambda sensor could cause timing retard but probably not boost reduction.

    My brothers having a similar issue but with his golf gttdi.

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  22. #21
    Sandip's Avatar
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    Might be barking up the wrong tree here but could it possible that the cars going in and out of limp mode? Possible fuel pump maybe? I somehow how think it isn't going to be the n75, i went through a stage of changing the n249, n75, the dv, fuel filter, temp sensor, maf (x3) to in the end find out i had a small split in one of the small hoses on the side of the inlet manifold, your problem seems to go on in off, maybe an uprated apr fuel pump kev?
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  23. #22
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    Quote Originally Posted by sandip View Post
    Might be barking up the wrong tree here but could it possible that the cars going in and out of limp mode? Possible fuel pump maybe? I somehow how think it isn't going to be the n75, i went through a stage of changing the n249, n75, the dv, fuel filter, temp sensor, maf (x3) to in the end find out i had a small split in one of the small hoses on the side of the inlet manifold, your problem seems to go on in off, maybe an uprated apr fuel pump kev?
    it does seem to be a soft limp issue but only way to clear is to disconect the battery, could be fuel pump which caused lamba code also, but id need mapping again with an uprated pump wouldnt i??

  24. #23
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    I wouldn't think you would, not 100% but i'd say uprating the pump would just get you 100% of the fuel your asking for, when your asking for max boost it might not be getting the full dosage it needs to get peak, the uprated pump would be able to cope with the demand of the extra fuel needed, you could probably get away with a new oem pump as yours might just be a little tired, but if my pump was on its last legs i'd go for an uprated one then atleast your fuelling never suffers, hope i haven't confused you lol
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  25. #24
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    But how does the fuel pump directly effect the boost? Does the ECU sense the lack of fuel and back off the boost as a result?

    I assume the 5psi differences are seen on the same day and not a few days in between. I know my car performs differently day to day! Perhaps not by that much though!!

    Interesting thread though
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  26. #25
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    Fair comment ianysm, don't think the pump will directly effect boost but i was just thinking if its going into limp maybe thats causing the poor boost pressure and maybe its going into limp because of the pump, S3's always tend to hide their problem behind other things! lol
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  27. #26
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    You could be right, the ECU might back off the boost as it tries to compensate for the lack of fuel pressure? Just guessing!
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  28. #27
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    Yep! Wonder where kev's hooked his boost gauge to? Fuel pressure regulator or the dv?
    3.2 V6 with Custom Code VVT Attack Software


  29. #28
    s3_kev's Avatar
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    Quote Originally Posted by ianysm View Post
    But how does the fuel pump directly effect the boost? Does the ECU sense the lack of fuel and back off the boost as a result?

    I assume the 5psi differences are seen on the same day and not a few days in between. I know my car performs differently day to day! Perhaps not by that much though!!

    Interesting thread though
    na the difference is night and day just the boost is the obvious sign of the problem the exhaust note is also different also the sound of the turbo spool is different along with the speed of turbo spool.
    its in a limp mode that im sure about as like i say it dosent get better once the problem occurs only way to clear the problem is to disconect the battery then it runs fine on full boost etc,,, untill the fault happens agian and i can tell when its gone before the boost drops right off as it struggles to peak boost for about 5 mins then its down on power again,

  30. #29
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    Quote Originally Posted by sandip View Post
    Yep! Wonder where kev's hooked his boost gauge to? Fuel pressure regulator or the dv?
    niether lol, its on the vac line that runs from under the inlet manifold to the n249 but before the valve to get vaccum pressure, dont worry i no not to use the dv line like most do

  31. #30
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    Good stuff! Kev when i put my boost gauge on i was advised on putting it on the fuel pressure regulator, its 'supposed' to get a more accurate reading. Are you still running the n249 bypass?
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  32. #31
    s3_kev's Avatar
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    n249 bypass is now removed back to using the n249, think i use the fpr line for something else but cant think how its all set up now though, the problem isnt the gauge reading incerrect as the whole car performs worse,

    i have also replace all four coil packs as well as i blew one and put in bkr7e plugs at the same time,

  33. #32
    s3_kev's Avatar
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    ok this fault is on going still,
    i have now got vag.com full version and have done some logging on the fuel trim etc,, it looks like im running rich or the lambda sensor is correcting something to make it run efficiently, i have a boost gauge fitted and the vaccum pull is -20 on warm idle maybe -21 but its always been around that figure so i dont think i have a vac leak otherwise id have though it would show up on my gauge, i also have a tool to check for boost leaks and there isnt any. so how can i still be getting -14 fuel correction on block 32 in vag.com somtimes its -17 could it be a simple lambda sensor fault???? idle correction isnt to bad though around 0.8 ish to 0.4 however when i checked it earlier it was 1.5
    if i clear the fault codes even though there isnt any then the fuel trim correction goes back to 0 again as it would and full boost is back for a brief while so it looks like the fuel trim could effect boost..
    anyone got any other ideas
    Last edited by s3_kev; 2nd December 2009 at 19:43.

  34. #33
    S3 Nattie's Avatar
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    My standard AMK show a vac of 20 at warm idle but after a while it goes to about 25 -27 according to my boost gauge.

    I would check the fuel filter and pump and the injectors.
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  35. #34
    s3_kev's Avatar
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    cheers going to have a look over it today

 

 

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