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B5 Boost Levels

Discussion in 'A4/S4 forum(B5 Chassis)' started by Drizz, Jul 21, 2009.

  1. Drizz
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    Drizz Project Plush

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    Just as a test i decided to see what boost my TQS was pushing.
    From 3k in second gear i got 9-10psi, in third gear 12-13psi and fourth 14psi
    I want more boost lower down :( lol
    Anyone else checked their boost in this way? Im interested in standard and remapped cars.....
    #1
  2. au_sjo
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    au_sjo Member

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    You don't fully load up the engine in the lower gears so you may not get full boost.
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    I think its more related to how the map/ecu controls the N75 valve to ramp the boost up. If you sealed off the actuator feed you'd probably spike 20+ psi in second.

    What you'd really want is the N75 to hold the wastegate shut until you reach max boost, then start controlling it, but it tapers the boost in slowly instead.

    I dont know if this is because the engine has no boost sensing, or if its just supposed to make the car more civilised to drive.

    You might find that an N75J will help bring the boost in harder, or perhaps converting to some other method of boost control, but if you bring it in too hard, you may well find you'll get fuel cut.

    A different remap might help too.
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  4. au_sjo
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    au_sjo Member

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    Closing the wastegate in first gear would make no difference.
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  5. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    I would say it would.

    In first your thru it that quickly the ECU will barely ramp the boost at all. Whereas no wastegate would see the turbo producing the maximum possible boost in the time available.

    Go pull your boost sense line and see what happens...
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  6. Geeman
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    Geeman Low Life

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    I've put a N75J valve on mine, plus a TT-225 DV, and I don't think it's made any difference to mine at all.
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  7. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    Drizz so you are chipped then? Boost levels depend on load . So the higher the gear, the higher the load.

    Drizz I can go out and check mine for you if you like 1,2,3,4 yeah? I am chipped

    Giles, i expect your ECU is compansating for the J valve and cancelling it out, as you get that soft limp with any N75 don't you?
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  8. Drizz
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    Drizz Project Plush

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    No mines standard...
    Yeah have a go see what you get...
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  9. Geeman
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    Geeman Low Life

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    When you say 'soft limp', I assume you're referring to the loss of turbo boost in the car!

    Yeah, it happens with all N75 valves. Rubbish!
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  10. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    J valves can cause boost cut, as they allow the MAF values (ie the boost) to climb too quickly afaik.
    #10
  11. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    Drizz, they are awfully high values for a std car even under load.

    I make
    1st 18
    2nd 22
    3rd 23
    4th 22 but not really enough of road for proper test, but these are the max spikes gradually lowering when nearing red line
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  12. mac1403
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    mac1403 Member

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    I would say the boost figures you have stated are very reasonable for a unmapped car. If I remember correctly standard boost would be around 0.8 Bar, which equates to about 12 PSI. Anyway its not about how much boost is generated its more important that it holds that pressure, hence the N75J valve.
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  13. Drizz
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    Drizz Project Plush

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    The figures i stated are what it holds. It doesnt spike as such, it peaks and holds...
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  14. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Mark: its a TQS mind, so it will run a little more than a stock AEB.

    I think its just mapped like that, gentle introduction of the boost to make it nice and refined to drive.

    The standard turbo will be able to hold 12psi thru most of the revs, once chipped up to 20psi though, it will drop off as the revs climb as the turbo cant flow enough air.
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  15. Drizz
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    Drizz Project Plush

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    so not worth a remap till i get a t28 then....
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  16. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    I thought it was 8 max for AEB and 11 max for TQS?

    My AEB map pulled around 12 PSI most of the time tbh. Maybe he is just lucky.

    Drizz as for re map, it depends how quickly you end up going T28, if its not for tears maybe you can justify the loss of £300 ish for a remap to the pay again to get the T28 mapped further down the road
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  17. Drizz
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    Drizz Project Plush

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    Id rather put the 300 towards the t28 i think
    Just got to find the correct version....
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  18. hiltoa
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    hiltoa VAG erfahren

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    Or maybe he has an N75J and doesn't realise it... :whistle2:

    If he's really lucky, he might find he has a 710N diverter valve too...
    Last edited: Jul 22, 2009
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  19. Drizz
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    Drizz Project Plush

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    Ahhh well ive removed the OE dump valve but its handy to know i have the other wotsit thingymagig whatever it is...
    #19
  20. Oranoco
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    Oranoco Well-Known Member

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    My AEB only runs 12psi chipped :( Need more boost. Especially when the Americans on Audizine are running 18psi on naff fuel
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  21. S4twiggy
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    S4twiggy Fully Certified Detailer!!

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    wot is the difference between the N75 and N75j?

    how can i tell wot boost my turbos are running at and wot would be the normal psi for the S4?

    lately i been thinkin my car is not running as she should be, its been quite flat feeling of late, id love to able to experience another S4 to compare wot it is like to mine, sometimes though the car pulls off like a rocket which is makin me wonder if something is not quite right with it.
    Last edited: Jul 22, 2009
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  22. Drizz
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    Drizz Project Plush

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    Ive just been told you cant remap the B5s they have to be rechipped. Thats not right is it??
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  23. S4twiggy
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    S4twiggy Fully Certified Detailer!!

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    how do i do a pressure test with a compressor?
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  24. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    Thats correct in this country, the us tuners somehow can flash them
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  25. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Oranoco: Naff fuel? The yanks octane rating system is different to ours, so you need to add ~4-5 on to a yank number to compare with the UK's rating. Yankee 91 octane is just the same as 95 here, and "premium" gas in the states is usually 93 octane, which is the same as 97/98 here.

    I think the yank cars have different ECU's to ours, hence they're flashable.
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  26. ian52
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    ian52 2000 a4 1.8tqs-yellow

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    i would like to put a t28 on mine but its the cost and hassle of getting it chipped thats stopping me.
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  27. Drizz
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    Drizz Project Plush

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    So really we shouldnt say remap we should be saying chipped!
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  28. Stringster
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    Stringster Missed gear

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    I thought the facelift B5's could be remapped though?
    Mine is a very early facelift so had to be chipped.
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  29. Drizz
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    Drizz Project Plush

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    Is youres standard other than the chip?
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  30. Oranoco
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    Oranoco Well-Known Member

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    I was not aware of this. Lesson learnt :thumbsup:
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  31. Stringster
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    Stringster Missed gear

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    It was at the time of the chip. Still is really, just a few small upgrades.
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  32. au_sjo
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    au_sjo Member

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    Our fuel is measured by RON only.. American is (RON+MON)/2.. they call it 'octane' but it's not really.


    With regards to flashing ECU's.. I think the problem lies more to do with UK tuners not actually knowing how to do it more than the ECU's being different.. Any ECU since about 1990 will be 'flashable', somehow, it's just down to someone to figure it out..

    Everybody thought thought you couldn't re-program the Ford EEC-IV ECU until I designed a programmer for it.. (without an external chip module)

    :)
    #32
  33. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    The ROM in the early AEB ECU's is NOT reprogrammable. Mappers have to remove the chip, burn the new map onto a NEW ROM and solder it back in.

    The biggest problem is that stocks of these early chips are becoming scarce.

    The later ECU's have a different ROM which isnt quite so rare, but afaik these also cant be erased, and need replaced.
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  34. docurley
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    docurley Moderator Staff Member Moderator

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    Stock 1.8TQ hitting 14psi is not standard in any gear so something is different in his car for sure and it may well be chipped already.

    14psi to 15psi is the most you will get from a chipped K03 without a bleed valve so I would say the cars performing well with those figures.
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  35. jcb
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    jcb Active Member

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    some do. some don't. the DBC ones are the same.
    I bought my replacement ECU from Tapp auto and it has the same code.
    They still chip them when required but there seem to be a lot more flashable later ECUs over there
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  36. au_sjo
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    au_sjo Member

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    Got the part number of the chip? :)
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  37. Drizz
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    Drizz Project Plush

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    If it is id hate to have driven it standard.
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  38. docurley
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    docurley Moderator Staff Member Moderator

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    LOL
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  39. Drizz
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    Drizz Project Plush

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    Soooooooooooooooooooo slow
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