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Boost/Hesitation problem...

Discussion in 'A3/S3 Forum (8L Chassis)' started by Welly, Sep 19, 2009.

  1. Welly
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    Welly VX220 SC Driver :)

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    [Sep 19, 2009]
    Before we start, I know most people's thoughts on Manual Boost Controllers. I appreciate why people don't like them, and understand the reason as well. However, I'm using one, so please don't start giving me the 'Just take it off and use the N75, let the ECU manage it' speech :). Also, sorry for the long post.

    Basically, using a MBC (well, bleed valve to be fair) to manage the boost on my AGU Engine. Its currently has the usual stuff, FMIC, REVO Stage 1, K03S.

    I wasn't getting the boost out of the K03s that I was hoping for (15 psi peak and dropping off substantially). Spoke to Badger who does my tuning, and we agreed that the boost was low, and logged the ECU using VAG COM. MAF readings show low air input and that the N75 cycle time was low as well.

    On went the bleed valve, and we had immediate problems. Basically, I've had to run it in reverse to get it to work, but it means that for the most part, the boost in uncontrolled. This sounding bad, isn't so bad, as the turbo never produces more than 20 PSI peak and just holds much better throughout the rev range.

    Great. Big smiles.

    Only issue is when under high load in 3rd or 4th (low revs for example, pulling up hill) the engine will stutter. This is the only time it happens, other then that, it's good as gold. I've replaced the 3 BAR with a 4 BAR FPR on it to test, still does it so I'm not sure it's fuelling (Stage 1 REVO map should peak around the boost I'm running, and the MAF is the only thing controlling fuelling really on the AGU - believe it should be OK)

    Haven't been able to VAG COM again yet, will do at earliest availability.

    Any other ideas? Fuel pump? Injectors?
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  3. marcyp
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    marcyp Only me

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    [Sep 20, 2009]
    try turning it down 1/4 of a turn take it out and see if it still dose it, some times the bleed valves tend to shake and undo a little bit over time and with the heat from the engine bay. so that would be my best bet, if that dosnt work check vagcom to see if your mafs out.
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