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Surging power? Why?

jimmy77 Nov 6, 2010

  1. jimmy77

    jimmy77 Registered User

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    Hi all, I've just got the revo remap on my B6 190 qts and it loads better but under soft acceleration the car flies but if I floor it it surges!! It's like your lifting on and off the throttle all the time!! Is this the diverter valve passing boost? It's a new standard one!! If so does anyone have a updated one for sale? Thanks!
     
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  3. crazypainter

    crazypainter Registered User

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    Take the pipe that runs off the DV into top of engine and blow down in, you will feel if the diaphram (sp?) is moving when you suck/blow. It can go at any time unfortunately! will give you flat spots etc thats my understanding anyway, sure someone can give a better/more accurate answer!
     
  4. jimmy77

    jimmy77 Registered User

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    Thanks cp, it's new n just tried that n seems ok, been told they pass the boost pressure so in affect it looses boost, is this true? I had a 205 turbotechnics running 225 bhp at the wheels with the same diverter valve and that was on 17 psi n ok!
     
  5. Q4

    Q4 Registered User

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    Jimmy,

    I have had a similar problem since I had my 1.8t revo'd. Mine is great on light throttle but if on full throttle around peak boost (3000 rpm ish) I get this surging / hesitating that you mention from then on throughout the rev range. I have replaced many things to get to the bottom of this including n75, uprated divertor valve, many solenoids, temp stats (intake and coolant), coil packs, spark plugs, 3X Maf's, fuel filter and Vac pipes but it still does it.

    After many Vagcom runs monitoring knock, intake temps, boost levels etc we have concluded that it's detecting pinking (Knock) and this surging is the timing being cut back by the ecu then being brought back in again. One theory we have at the moment is that under full throttle it's not getting enough fuel so leaning out on peak boost, pinking then getting into this hesitation / holding back cycle!

    I have even monitored real time fuel pressures and it always meets required book pressure but a fuel pump can give correct pressure but not give correct flow. As yet I have not replaced the fuel pump relay (next on the list) or fuel pump itself to see if that is the cure.

    To note a good super unleaded fuel will lesson this effect due to its high octaine, I have turned down my revo settings to those below the standard Boost 6 timing 2 and still get this problem.

    I have spoken to various people about this problem and it has been suggested that the duel mass flywheels can start to break up and cause knock but this is normally only detected on cylinders 3 & 4 mainly high on 4. I get the same levels of knock across all 4 cylinders so that rules that one out for me!

    Pm me if you want any more info, this might not be exactly the same thing that is happening to your car but it might help point you in a certain direction.

    If you do solve this problem before me let me know !
     
    Last edited: Nov 7, 2010
  6. jimmy77

    jimmy77 Registered User

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    Thanks for the reply that's helped loads, after I got home I rang revo and they said it was the diverter passing boost but by the amount of things you have changed I may look into it lots more, did the diverter make any difference? Sometimes it's fine, really pulls hard but them it's up and down down you say if somones on and off the gas!! Strange one that isn't it, the car was mint before the map just flat, just got in now from a run and it's feels like lots if lag then bang loads of boost n it's off but then starts to surge!! The revo is on 4 at the mo but was told I would get 6/7 if I got the full remap!! Will try and borrow a mates forge d/v and see if that helps!! Will keep u posted tho and thanks for that info
     
  7. Q4

    Q4 Registered User

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    I put on an uprated diverter valve (forge if I remember correctly) befor I had the car re-mapped knowing that these are a weak spot. My hesitation is not aggresive but but would describe it as wave like. I know my boost levels are correct as the vagcom logs show requested and actuall boost levels are always close or matching.

    If you haven't upgraded the diverter valve then that would be a good point to start from as it is a known problem with all 1.8t engines even at standard boost levels.

    Good luck in getting to the bottom of this, let us know how you get on
     
  8. jimmy77

    jimmy77 Registered User

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    Thanks mate, yeh mines a hit of power then turns into waves! Will try some things and get vagcom on it but it's new to me so not really sure what I am doing, will vagcom show a fault with the d/v or just list it lowering boost? Will play tomorrow n c what I can find!!
     
  9. jimmy77

    jimmy77 Registered User

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    Just a update, my car lost all go and was the same as it was before the remap, I still hav around 200 miles left on the trail remap so had a look with vagcom, it showed up thermostat faulty and intake air temp sensor faulty, something with bank one oxy sensor!! Changed the air temp sensor but no improvement, did thermostat and still the same, fitted a forge dv and still the same!!! Tried all the different springs in the dv but still didn't get the power back!! Do I need to clear the faults with vagcom for it to reset it's self to poss bring back the power? Or will it reset it's self? It's doing my head in, can't find any boost leeks and there's no faults related to this but still no boost!! Arrrhhh
    I read in another post that I guy bypassed his n75 but will this just giv unlimited boost as what the turbo can produce? I know what the n75 looks like but which one is it as there's two the same!! Thanks
     
  10. Q4

    Q4 Registered User

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    The reason for lack of boost may be just down to the fact that the revo trial as finished. Fault codes normally have to be reset after component replacement but this may or may not have an overall effect depending on the system effected.

    Bypassing the N75 isn't advisable and can lead to other issues not just putting the car in to limp mode. There are a few pictures on here to show you the location if you do a search for it.

    I now how frustrating this is especially as nobody can say without doubt what the problem is !

    On another note if you are still in two minds about a remap, if I was to do it again I would personally go with an APR map. A different map would not of solved my problem I just prefer the way it delivers the power in comparrison to the revo map.
     
  11. jimmy77

    jimmy77 Registered User

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    thanks Q4 i have checked my mileage and time used and i still have loads of trial left, well if its correct what they say! will clear the faults tomorrow and see if its sorted it,am swaying towards getting the remap done with a rolling road just so i can make sure its set up just as i want it.
     
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  13. Q4

    Q4 Registered User

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    *UPDATE*

    Well replaced the fuel pump after the last one packed up and left me at the side of the road. I was hopeing that a weak pump would of been the cause of the cars hesitation problems............

    So pump replaced and test drive carried out and still have exactlly the same problem as before. Car still hesitates at around peak boost (3k-3.5K ish) and vagcom still detects knocking/pinking.

    The search still continues for a cure............
     
  14. hartey

    hartey Registered User

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    I feel for you mate, I am having exactly the same probs as u are describing, I thought it was a clutch problem at first, then realised I have a multitronic with no clutch! Anyway, went to Driver Transmission in Birmingham, and Amarjit doesnt think its gearbox related (what this man doesnt no about autoboxes, isnt worth knowing), so I am back to square 1,

    booked in tomorrow for vagcom, i already no my stat is playing up, so lets c what tomorrow brings,

    Did you get to the bottom of your prob?
     
  15. jimmy77

    jimmy77 Registered User

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    hi mate ,well i changed my stat and intake air sensor but it was still the same, i took it to a mate and the air intake sensor and the stat were plugged in the wrong connectors!! the only two you can get wrong and someone had!! so swapped them and cleared all faults and still the same!!! i was told to do a master ecu rest, i havnt done this yet but hope this might help!! i have noticed that mine accelerates quicker in 4th rather than 3rd!! i need to get this sorted this week as going in for a revo remap before xmas!!!
     
  16. hartey

    hartey Registered User

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    ok thanks, going for diagnostics later, will let u no how i get on.
     
  17. jimmy77

    jimmy77 Registered User

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    Well today I had revo come and fully map the car, it's got rid of the surging for now!! Hope it has cured it fully, cars going really well too!! Hope it keeps this way!!
     
  18. hartey

    hartey Registered User

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    Ok well done on fixing yours, die'ing of swine flu at the min so couldnt get to the mechanic! Hope yours stays well.
     
  19. j033y

    j033y Registered User

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    Good man, hope it's sorted, you'll have too take me out in it, see if it makes me want mine chipped.
     
  20. jimmy77

    jimmy77 Registered User

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    Yeh mate I will do, if u have £199 get it done before this offer runs out, after a quick blast I lifted the bonnet and the turbo was glowing orange!! My 205 turbotechnics used to do that!!
    Hartey I hope u get yours sorted soon, I can ever so slightly feel a surge as the n75/ wastegate level out the pressure but it is pulling like a train this time not backing off!! Will keep you updated if it changes!!
     
  21. hartey

    hartey Registered User

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    Hope I do get it sorted, not enjoying driving the car at all!!

    By the way am i doing any damage by driving the car?
     
  22. crazypainter

    crazypainter Registered User

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    whats the car putting out with the remap? and before?
     

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