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Thread: Boost drop off at higher rpms..

  1. Default Boost drop off at higher rpms..

    Tim,

    I have observed that while on the dyno the boost hits hard and then drops off over 5K. Is this normal?

    Thought this TVS blower was good for 16+ psig and didn't expect a drop off at this level of boost.

    It made about 13.5 and drops off to 11.

    Car made 601/617 with just the pulley kit and some minor tune changes. Will post sheet when I get a chance.

    Howard

  2. Default ZR1 Corvette LS9 boost drop off

    Howard,

    It sounds like you might be hitting the overboost limits in the calibration.

    To fix this you need to change the high and low limits in the overboost protection area.

    In EFILive it is the following locations:
    B7006 Overboost Upper Limit
    B7007 Overboost Lower Limit

    On the ZR1 we set them to 230.0 kPa (B7006) and 210.0 kPa (B7007).

    Stock is 192.0 and 172.0 kPa.

    To confirm that this is what is causing the problem, you can log or view the boost control solenoid activity with a scan tool or data acquisitition software. I am fairly certain a Tech 2 shows this variable but I don't recall what it is called.

    In EFILive the variable is:
    Description: Supercharger Boost Solenoid Duty Cycle
    Caption: SCBDC
    System: Conditions
    Parameter: GM.SCBDC

    I can get you the variable and location names in HPTuners or other software if you need them in some other format.

    If this doesn't solve the problem, get us a data log of the problem happening and we can take a look at it. I can send you an EFILive PID list of variables to monitor if that helps.

    Hope this helps.


    Jason Haines


    Quote Originally Posted by Redline Motorsports View Post
    Tim,

    I have observed that while on the dyno the boost hits hard and then drops off over 5K. Is this normal?

    Thought this TVS blower was good for 16+ psig and didn't expect a drop off at this level of boost.

    It made about 13.5 and drops off to 11.

    Car made 601/617 with just the pulley kit and some minor tune changes. Will post sheet when I get a chance.

    Howard

  3. Default

    Jason,

    Thanks for your reply. I found the over boost limit twice! LOL! The first time was on the first dyno pull with the pulley as we nailed 192 Kpa no problem! I had raised it to 202 and hit that on the street on a cold morning and boostin' hard in first gear. According to the stock MAP sensor we reported a max boost of 14.8 or I believe 203 Kpa so we bump that overboost limit again to 210.

    The issue we are seeing is not a sharp drop as if we hit the limit. I have seen that once you hit that max limit {B7006} the engine defaults to about 5.5 psig. This is not what we are experiencing. How does the boost lower limit {B7007} tie into this?

    We we seeing a surge of boost between 2000 and 4500 (191 Kpa/13.2 psig) and then a gradual drop off to 6500. We are reporting average boost above 4500 to 185 Kpa/12.4 psig.

    It also boosted higher on the street with reported peak boost of 14.8/202 IAT's where 73 and the motor was loving it!

    Using EFIL as well.

    Howard

  4. Default HPTuners calibration changes

    If you are using HPTuners then you need to change the variables in the following area:
    Engine
    - Torque Management
    - - Supercharger

    Then go to the following section of the "Supercharger" tab:
    - Boost Disable

    In the "Boost Disable" section you will have the following stock data:
    MAP Disable: 192 kPa
    MAP Enable: 172 kPa

    Change these to:
    MAP Disable: 230 kPa
    MAP Enable: 210 kPa




    Jason


    Quote Originally Posted by Jason@Lingenfelter View Post
    Howard,

    It sounds like you might be hitting the overboost limits in the calibration.

    To fix this you need to change the high and low limits in the overboost protection area.

    In EFILive it is the following locations:
    B7006 Overboost Upper Limit
    B7007 Overboost Lower Limit

    On the ZR1 we set them to 230.0 kPa (B7006) and 210.0 kPa (B7007).

    Stock is 192.0 and 172.0 kPa.

    To confirm that this is what is causing the problem, you can log or view the boost control solenoid activity with a scan tool or data acquisitition software. I am fairly certain a Tech 2 shows this variable but I don't recall what it is called.

    In EFILive the variable is:
    Description: Supercharger Boost Solenoid Duty Cycle
    Caption: SCBDC
    System: Conditions
    Parameter: GM.SCBDC

    I can get you the variable and location names in HPTuners or other software if you need them in some other format.

    If this doesn't solve the problem, get us a data log of the problem happening and we can take a look at it. I can send you an EFILive PID list of variables to monitor if that helps.

    Hope this helps.


    Jason Haines

  5. #5

    Default

    EFI Live Over Boost Settings - updated

    B7006 change to 256
    B7007 change to 250

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