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N75? Strange Boost

Discussion in 'A3/S3 Forum (8L Chassis)' started by Sam_, Oct 31, 2013.

  1. Sam_
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    Sam_ Down under

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    I don't have a boost gauge fitted (other than the liquid gauge) but recently I've been noticing some strange behaviour. I'll be driving at part throttle pulling away slowly and the turbo will spool up really early as if there's much more load than there actually is. You can hear it dump boost sometimes too. It's very strange. I also think I'm getting overboost which is causing the knocking (which is now almost permanently if I give it some).

    Could the strange spool behaviour be the N75? It drives fine otherwise.

    I'm fitting a brand new OEM pump at the weekend in the hope that it might be the cause of the knock (lack of fuel).
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  2. [Dave B]
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    [Dave B] Rrrrrrrr-tech

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    Does it suddenly drop power when this happens, and is it happening in 1st and 2nd gear?
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  3. Sam_
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    Sam_ Down under

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    It usually happens as I come up the ramp out of the work car park, so first gear. It's hard to explain but basically you can hear what sounds like the turbo spooling up and making boost yet I am going really slowly, and then it dumps by itself and returns to normal behaviour. It's very odd. Only happens occasionally and it's me being OCD that wants to sort it out.
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  4. Westy
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    Westy Double Dark Side! Diesel & 8P

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    I had this exact same issue when my car was cold. I investigated the DV (007p) and realised that a blue spring had been put in there when it was mapped and that half the metal piston had been rubbing where it was sticking. anyway I fitted an OEM valve and it's been fine ever since. Go check your DV for signs of wear or sticking.
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  5. Sam_
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    Sam_ Down under

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    Good call. It could be that the spring in the Tial is too strong. I do get the odd bit of flutter. Hmm.
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  6. Westy
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    Westy Double Dark Side! Diesel & 8P

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    It was driving me mad and then I noticed the car was jerky on part throttle in 5th/6th on the motorway. A new valve stopped all this weirdness.
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  7. Sam_
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    Sam_ Down under

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    Cool. Might chuck an OEM on there for now. it's not like I "need" the Tial on there yet.
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  8. Westy
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    Westy Double Dark Side! Diesel & 8P

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    An OEM valve will prove if your DV is the issue as its a sealed unit that can't be played about with. Hope it sorts your issues. I found part throttle was sooooo much smoother with the OEM valve. Love it.
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  9. Sam_
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    Sam_ Down under

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    Awesome. Sounds like it's the same thing perhaps. I'll grab a 710N and go from there then.
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  10. Westy
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    Westy Double Dark Side! Diesel & 8P

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    Any luck with this Sam? My car has started to do it again even with the OE DV but my mrs keeps filling the car with 95ron fuel so I think it's that. Only when cold though :think:
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  11. Sam_
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    Sam_ Down under

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    I've not had a chance really. The weather last weekend was insane, pure rain and storms. I should venture out this weekend and grab a 710N and some new plugs (unrelated) but there's some good swell coming in so I might go grab some surf shots if the weather is good.

    I'm going to order a 8-9psi spring for the Tial QR in the meantime anyway as I have the 11psi one which is clearly too stiff. A bit of reading on Vortex etc shows that the 8-9 psi one is the way to go. I told the guy when I bought it that the 1.8T was lower vacuum but he was all 'it'll be fine'.
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  12. badger5
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    badger5 RIP S3dave Site Sponsor

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    95UL?

    owch!
    when max'd out on the map on 99?
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  13. Prawn
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    Prawn My other car is a MINI!!!!

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    95 ron in that is some scary **** Westy. you need to educate her!
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  14. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Take the keys off her and tell her to walk.

    Putting the right fuel in isnt ****ing hard, if she cant do it right she shouldnt be driving.
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  15. superkarl
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    superkarl MAN OF STEEL

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    What sort of timing would it be pulling from 99map on 95? That bad?
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  16. Sam_
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    Sam_ Down under

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    I'm sure it was an honest mistake :)
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  17. Westy
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    Westy Double Dark Side! Diesel & 8P

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    I've educated her but she don't give a **** and just puts the cheapest stuff in :(

    Obviously she doesn't drive it like its meant to so hopefully it'll be ok. The map should just pull all the timing. I'm sure it was mapped on 97ron anyway as the closest garage to RTech is a BP that does Ultimate (which isn't reall Ultimate).

    I need to get the keys off her!
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  18. badger5
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    badger5 RIP S3dave Site Sponsor

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    could have been worse and diesel'd it by mystake
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  19. badger5
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    badger5 RIP S3dave Site Sponsor

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    I have seen CF or 6 easily on 99 to 95, and if tuned to see up to 6cf on 99, then you can do the maths.... It would consume the std 12CF it can pull max
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  20. Sam_
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    Sam_ Down under

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    I finally got around to replacing the 10 psi spring in the Tial today with an 8 psi one. Seems it no longer flutters at low rpm/throttle and it already seems smoother. Time will tell tomorrow when I pull out of work. I was going to buy an OEM 710 but they were like $50-60 here and a new spring for the QR was only $35.
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  21. Sam_
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    Sam_ Down under

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    Way way way better with the 8 psi spring. It no longer seems to do the weird boost at low rpm thing. It must be getting bled off or something. It doesn't seem to be surging either which has mean the knocking I had has stopped. More testing required to confirm but I think that solved it.
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  22. Westy
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    Westy Double Dark Side! Diesel & 8P

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    I hope my Xmas pressie is in the post for helping you with this issue ;)
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  23. Sam_
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    Sam_ Down under

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    haha of course mate ;)
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  24. Sam_
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    Sam_ Down under

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    Spoke too soon. It still does it. Bloody thing. It is still smoother though. I'll have to order an N75 valve and fit this new OEM fuel pump I have (might be the cause of the pinking but doubtful?).
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  25. Sam_
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    Sam_ Down under

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    I just cleaned the MAF with isopropyl alcohol and no noticeable change.

    The pinking issue is the most worrying. It's been on and off for a while now and mainly seems to do it under one kind of scenario, when I build up slowly or hold RPMs on the edge of boost and then nail it. It's like there's a massive requirement for fuel which perhaps the pump can't meet. All the major "usual suspect" parts have been replace 12-18 months ago, only the pump hasn't. The thing is, if it was the pump the ECU would cut timing correct? Perhaps I'm hitting the maximum it can pull and it can do no more.

    I really need to get the SPA fuel/boost pressure gauge setup as I don't really 100% know what's happening with boost. The liquid gauge measures 1550 which I think is the max it can read. Realistically though, fitting the new OEM pump I have is probably easier as getting the big sensor connectors from the cabin through to the engine bay won't be easy. I have the pump without the level sensor and top part attached so it's a bit of extra work to change the pipes over. I've just been waiting for a low tank to do it. I'll stick in a new fuel filter at the same time and see if that helps. Bloody thing.
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  26. Sam_
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    Sam_ Down under

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    Just worked out I got ~30 mpg on the last tank. Seems high? It gets a bit of stick most days but rarely pinks.
    Last edited: Dec 15, 2013
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  27. Sam_
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    Sam_ Down under

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    Does anyone know a decent forum I can get some help with issues like this? Would be good to hear if other people have had the same issue.

    I'll replace the fuel pump tomorrow and go from there I guess.
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  28. badger5
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    badger5 RIP S3dave Site Sponsor

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    what % load does it think its running on.. block 002... 003 for timing actual, 020 for CF corrections,
    #28
  29. Sam_
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    Sam_ Down under

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    Cool cheers Bill, I'll do some logging later tonight.
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  30. Sam_
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    Sam_ Down under

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    Here's the logs. It was a bit hard to actually do a proper full run in 3rd so some were in 2nd and I rarely took it to redline purely because of where I was. It's a tiny bit cooler tonight and I didn't hear any knock at all and it felt pretty strong (saw ~222g/s on one run without taking it too high rpm wise). I wonder if it's purely IAT related and WMI might have to be considered?

    [​IMG]

    I also managed to log 001, 002, 031 by accident on my first run, not sure if that's of any use.

    [​IMG]
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  31. Sam_
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    Sam_ Down under

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  32. Sam_
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    Sam_ Down under

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    Guess I'll just have to leave it be for now and wait until I fit the new engine. I haven't got a clue what's up and taking it to an "expert" here would be a dead end.
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  33. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Sorry dude been a bit busy at work and a little wasted now... will make the effort to review your logs and comment in the morning...

    <tuffty/>
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  34. Sam_
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    Sam_ Down under

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    Thanks mate - it's quite a weird one. Any help is appreciated!
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  35. Sam_
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    Sam_ Down under

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    Replaced the fuel pump today and some new BKR7E's gaped to .032". Took it for a quick spin and couldn't get any knock, although it's not done it for a few days anyhow. Time will tell.
    #35
  36. Sam_
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    Sam_ Down under

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    Not sure if it was the fuel pump or the other little bits I've done recently but drove to a mates today for a Christmas BBQ and it felt epic driving back through the national park. Some nice sweeping open roads and even got to try a launch (been a while) and it feels very strong. Logged the most it ever has...

    [​IMG]
    #36

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