Overboost problem?
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  1. #1
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    Overboost problem?

    I have a 98 passat 1.8 w/ 1.0 wetchip, n75j, and tt dv. (no exhaust mods and stock air filter and box)

    For the past two weeks my car has been having a disturbing problem: when I accelerate the engine bogs out when under medium to high psi's, usu. 13-20 psis's. Note, this problem is most prominent in 5th gear, although it has happened in 4th occasionally, 3rd once, and never in the lower 2 gears.

    When I say the engine bogs out, I mean that for only a split-second there is a almost complete dropoff in power, then the engine returns to normal operation, although this problem has occurred in succession many times, once again, most notably in 5th gear.

    Futhermore, this problem has semed to coincide with the cold weather. I live in Southeatern Pa, and the weather has gotten cold very fast. I have never had this issue during the summer; howver, I've only had the wetchip and n75j for under 2 months, so whether this is a weather tempature problem or time/duration problem remains in doubt.

    I've read about the overboost issue, i.e. when your car can't get more than 5 or so psi's, and the car must be shut off to reset the ecu, but this is not my problem, but I was still thinking that it is somehow related to overboost. I'm wondering if my engine is getting enough air. Also, I've thrown no cels.

    I welcome as much info. as possible. Thanks, Sam

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  3. #2
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    You're going into soft limp.

    Sounds like Overboost to me.

    Get a MBC adn a Boostgauge.

  4. #3
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    Have you emailed Kelly at Wett about this? I'll bet she would have some good feedback for you. I have the same chip and my 99 1.8t. I am getting ready to install a N75 j or H valve soon, so it would be nice to hear more about what solves your overboost limp mode.

    good luck keep us posted

    Bob

  5. #4
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    Check out this thread, wherein I post up a couple of erudite ditties concerning N75's, overboost, and MBC's: Who's using an MBC/Boostvalve?

  6. #5
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    You're going into soft limp.

    Sounds like Overboost to me.

    Get a MBC adn a Boostgauge.
    I have an Autometer boostgauge--put it in the same time as the chip How would a MBC solve the overboost issue?

    Clarification wanted: I've read and heard that when your car undergoes limp mode the ecu must be reset via shutting off car. Then I've heard that the car doesn't have to be shutoff get out of limp mode. Are both cases correct, meaning that each experience of limp is unique?

    Also, just to further clarify my problem, the engine boggs for < than 1 second, then all power is regained continually. I assume this is what you called soft limp mode as opposed to full limp mode?

    So if in fact this is a soft limp overboost issue, how can it be resolved? Thanks for the feedback, Sam.

  7. #6
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    What you can do is install your old N75 during the winter then put back the J when it starts getting warmer outside. That's what I do.

  8. #7
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    I'm not doing that. I like power tooooooo much.

  9. #8
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    Turbo like the cold. I doubt you will feel that much of a difference

  10. #9
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    The AEB has no boost sensor, it determines boost by comparing actual MAF to specified MAF. In the colder weather, less boost is needed to achieve desired MAF readings. With the N75J you are causing a boost overshoot, which the car will see as a MAF overshoot.....colder weather = greater overshoot = greater chance to hit limp mode.

    if you want more boost ask Kelley to make you a hotter chip vs. using the N75J.

  11. #10
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    Quote Originally Posted by scotty_passat
    The AEB has no boost sensor, it determines boost by comparing actual MAF to specified MAF. In the colder weather, less boost is needed to achieve desired MAF readings. With the N75J you are causing a boost overshoot, which the car will see as a MAF overshoot.....colder weather = greater overshoot = greater chance to hit limp mode.

    if you want more boost ask Kelley to make you a hotter chip vs. using the N75J.
    Spot-on. Yay, Scotty! :bow:

  12. #11
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    colder weather = greater overshoot = greater chance to hit limp mode
    so it's safe to say I won't need to worry about this in FL?

  13. #12
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    Wow, I had the exact same problem and I'm running the same setup as the guy who started this thread. It was 27 degrees the other night when I was coming home from work, and the car literally felt like I hit a wall when I'd give it some. I've got a busted motor mount so when I hit fuel cut, it felt like my engine was going to fly out from under my hood. I still am waiting to purchase a boost gauge so I have no idea what's going on for certain. What PSI does the car consider 'overboosting'? I'm curious, I wouldn't think I'd have more than 16-17psi with the Wett chip and n75j.

  14. #13
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    Quote Originally Posted by sac201
    You're going into soft limp.

    Sounds like Overboost to me.

    Get a MBC adn a Boostgauge.
    I have an Autometer boostgauge--put it in the same time as the chip How would a MBC solve the overboost issue?

    Clarification wanted: I've read and heard that when your car undergoes limp mode the ecu must be reset via shutting off car. Then I've heard that the car doesn't have to be shutoff get out of limp mode. Are both cases correct, meaning that each experience of limp is unique?

    Also, just to further clarify my problem, the engine boggs for < than 1 second, then all power is regained continually. I assume this is what you called soft limp mode as opposed to full limp mode?

    So if in fact this is a soft limp overboost issue, how can it be resolved? Thanks for the feedback, Sam.
    Okay, here goes...

    a Manual Boost Controller will allow you to "dial down" your boost spikes. I use mine as a precautionary measure because I can hit 24psi spikes easily (23.9 psi seems to be the max the ECU will recognize before cutting into soft limp, so I hope that answers another person's question posted above.) With the MBD my boost spikes now at a safe 22 psi.

    There are two different limp modes, hard and soft. With hard limp mode you DO have to shut off the car, and disconnect the battery to reset the ECU. I've never heard of anyone waiting around to see how long it takes to automaticly reset. With sodt limp, the ECU can limit the ammount of boost from a second to several hours. You essentially can be in soft limp through a few different engine starts.

    So, to ask you another question, the power loss you're feeling...

    Do you have to let your foot off the throttle and then you're boosting again, or even if you're at WOT, the engine drops power, and restores it.

    I've found time and time again, that it AT LEAST takes one to take their foot off the throttle, and then proceed to accelerate again for the ECU to "regain it's senses" at reset the soft limp. Sometimes I've even had to downshift in order for the boost to come back.

    thats all I have for ya. Maybe Rusty can add more.

  15. #14
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    Quote Originally Posted by Spanky McGee
    ...thats all I have for ya. Maybe Rusty can add more.
    Why, Thank You for the introduction, kind sir! :bow:

    Quote Originally Posted by VWinOrlando
    colder weather = greater overshoot = greater chance to hit limp mode
    so it's safe to say I won't need to worry about this in FL?
    It's safe to say you might not need to worry about this in FL. Seems the main problem with overboosting in FL is related to voting machines...

    Quote Originally Posted by FormerGSRdriver
    ...What PSI does the car consider 'overboosting'? I'm curious, I wouldn't think I'd have more than 16-17psi with the Wett chip and n75j.
    There is no set psi that is considered "overboosting". It could happen at 5 psi if your ECU is only asking for 2 psi. It's all dependent upon actual airflow vs. expected airflow for a given rpm and throttle position. If you haven't read my post from the link I gave above, read it. If you've already read it, read it again, and again, if necessary.

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