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  1. #1
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    Unhappy JB4 Question: Jerky at part throttle

    Hello,

    I have a 2008 335i sedan automatic with 19,000 miles on the car, with JB4 running map 1 with 93 octane Mobil, and the tune was installed at around 18,000 miles. I'm in South Florida (weather?)

    Question: When I give the car about 50-75% throttle, if I am in D, DS, or manual (Happens in every mode) I get this wierd jerkyness. The car feels like it's going back and forth. Full throttle, no problems at all, smooth as butter. No codes, and the JB4 boost gauge shows 3/4 of a tank so the boost is there.

    On map 0, this does not occur. Any ideas?

    Thanks guys

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    i was experiencing the same with G4 board. Terry told me to take some logs and send them to him but i never got the chance.
    07 335i AT - MOTIV 750 - MHD BMS E85 - BMS PI - JB4G5 - Okada Coils - NGK 5992 Plugs - Helix IC - Stett CP - Custom midpipes with 100 HJS Cats - Bastuck Quad - PSS10 - QUAIFE LSD - BMS OCC - Forge DVs - AR OC - ALCON BBK - M3 Chassi - Dinan CP - Velocity M rear Toe arms - Advan RZ-DF - LUX H8 - Level 10 AT upgrade
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  3. #3
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    If you wind up needing any help just email a CSV log in.
    Burger Motorsports
    Home of the Worlds fastest N20s, N54s, N55s, N63s, S55s, and S63s!

    It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please see http://www.burgertuning.com/emissions_info.html for more information on legal requirements related to use of BMS parts.

  4. #4
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    Click here to enlarge Originally Posted by E90Company Click here to enlarge
    Hello,

    I have a 2008 335i sedan automatic with 19,000 miles on the car, with JB4 running map 1 with 93 octane Mobil, and the tune was installed at around 18,000 miles. I'm in South Florida (weather?)

    Question: When I give the car about 50-75% throttle, if I am in D, DS, or manual (Happens in every mode) I get this wierd jerkyness. The car feels like it's going back and forth. Full throttle, no problems at all, smooth as butter. No codes, and the JB4 boost gauge shows 3/4 of a tank so the boost is there.

    On map 0, this does not occur. Any ideas?

    Thanks guys
    I've noticed the same thing on mine as well. Been like that since day 1. I honestly always thought it was my foot not staying in one spot. Maybe do a log and see if the pedal fluctuates when your trying to maintain a specific pedal position.

    Only 19,000 miles for a 2008, nice!
    2008 E90 335i 6MT | JB4 G5 ISO | BMS Back End Flash | BMS DCI | BMS DP's | COBB Exhaust | VRSF 7" FMIC | BMS OCC

  5. #5
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    Thank you guys for the advice.

    Click here to enlarge Originally Posted by enrita Click here to enlarge
    i was experiencing the same with G4 board. Terry told me to take some logs and send them to him but i never got the chance.
    Good to know. Thanks. I will probably just log and see where my car stands.

    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    If you wind up needing any help just email a CSV log in.
    Thanks for the help Terry. Will do!

    Click here to enlarge Originally Posted by SJ_1989 Click here to enlarge
    I've noticed the same thing on mine as well. Been like that since day 1. I honestly always thought it was my foot not staying in one spot. Maybe do a log and see if the pedal fluctuates when your trying to maintain a specific pedal position.

    Only 19,000 miles for a 2008, nice!
    That's what I thought it was in the beginning as well! I am going to have to do a log when I find the time and send to the man.

    On a side note, how do you like the BMS downpipes?

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    Click here to enlarge Originally Posted by E90Company Click here to enlarge
    On a side note, how do you like the BMS downpipes?
    I think they're great. I had no issues with fitment other than having to remove the O2 sensor harnesses from the mounting clips to give them some more slack.
    2008 E90 335i 6MT | JB4 G5 ISO | BMS Back End Flash | BMS DCI | BMS DP's | COBB Exhaust | VRSF 7" FMIC | BMS OCC

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    Try stacking a linear Cobb map with the jb4 it will smoothen it out nicely. Part of the issue is the jb adds duty cycle on the stock tune which will result in perceived jerkiness.

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    Click here to enlarge Originally Posted by themyst Click here to enlarge
    Try stacking a linear Cobb map with the jb4 it will smoothen it out nicely. Part of the issue is the jb adds duty cycle on the stock tune which will result in perceived jerkiness.
    Wish I could

    So basically this will always happen unless I go with your suggestion with COBB? Or is there something I could do to fix it, running the JB4 only?
    Thanks

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    Click here to enlarge Originally Posted by E90Company Click here to enlarge
    Wish I could

    So basically this will always happen unless I go with your suggestion with COBB? Or is there something I could do to fix it, running the JB4 only?
    Thanks
    These are all blanket statements without seeing logs it's mostly blind advice. I'd start with dropping lag fix and boost gain to 40 and 15 respectively. It may smoothen out that lurchy on/off feeling.

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    Click here to enlarge Originally Posted by themyst Click here to enlarge
    These are all blanket statements without seeing logs it's mostly blind advice. I'd start with dropping lag fix and boost gain to 40 and 15 respectively. It may smoothen out that lurchy on/off feeling.
    Oh ok. Thanks for the tips

  11. #11
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    Click here to enlarge Originally Posted by themyst Click here to enlarge
    Try stacking a linear Cobb map with the jb4 it will smoothen it out nicely. Part of the issue is the jb adds duty cycle on the stock tune which will result in perceived jerkiness.
    Actually the problem with part throttle oscillation is normally not enough duty cycle on the JB4 side, resulting in the DME going in to a oscillating duty cycle condition as it operates at the high end of its duty cycle table. It's easy to spot in logs as JB4 PWM will be sitting at 0 while DME duty cycle and throttle are oscillating. It's also easy to resolve. There is a table on the JB4 firmware that we tweak from time to time. So if the problem crops up just send a log in and we'll make a note to adjust that part of the table in the next firmware release.
    Burger Motorsports
    Home of the Worlds fastest N20s, N54s, N55s, N63s, S55s, and S63s!

    It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please see http://www.burgertuning.com/emissions_info.html for more information on legal requirements related to use of BMS parts.

  12. #12
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    I notice it to. I just havent logged it. Was going to one day and it wouldnt do it.I notice it on 1/2 to 3/4 throttle accelerations. Also hear synapse bov holding and releasing until i apply more throttle or back out.This is holding throttle at a steady position.Seem to notice it more on the first acceleration of any more than 1/4 throttle when leaving after warm up.

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    I actually thought it was a issue with my car because i had not seen anyone post about it. I upgraded to a synapse bov because i thought it was a issue with the crappy z-shift that was on there.lol Love the charge pipe but that bov is junk.

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    Click here to enlarge Originally Posted by jzeee037 Click here to enlarge
    I notice it to. I just havent logged it. Was going to one day and it wouldnt do it.I notice it on 1/2 to 3/4 throttle accelerations. Also hear synapse bov holding and releasing until i apply more throttle or back out.This is holding throttle at a steady position.Seem to notice it more on the first acceleration of any more than 1/4 throttle when leaving after warm up.
    Thanks for letting me know I wasn't going crazy and feeling things, lol Click here to enlarge. Seems like a normal thing then.

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    Yeah i guess so. Do you notice it more when you first accelerate when you get in it for the day? Mine actually seems to not do it as bad after that. Also do you hear your bov or diverter release and the hold over and over until you change throttle input?

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    My car was being jerky at part throttle on the highway and 3rd-4th gear 60+mph.. Wouldnt happen on map 0, I updated my firmware and it went away.
    Send a log in, Terry will def. help you out.
    ///M5 LCI
    "It's like the F10 is the 911 Turbo to the E60's GT3" -Pistonheads (M5 feature)

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    Click here to enlarge Originally Posted by 5soko Click here to enlarge
    My car was being jerky at part throttle on the highway and 3rd-4th gear 60+mph.. Wouldnt happen on map 0, I updated my firmware and it went away.
    Send a log in, Terry will def. help you out.
    Cool, likes a firmware upgrade is necessary for those experiencing this.

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  18. #18
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    Click here to enlarge Originally Posted by jzeee037 Click here to enlarge
    Yeah i guess so. Do you notice it more when you first accelerate when you get in it for the day? Mine actually seems to not do it as bad after that. Also do you hear your bov or diverter release and the hold over and over until you change throttle input?
    What you said is exactly what i'm experiencing

    Click here to enlarge Originally Posted by 5soko Click here to enlarge
    My car was being jerky at part throttle on the highway and 3rd-4th gear 60+mph.. Wouldnt happen on map 0, I updated my firmware and it went away.
    Send a log in, Terry will def. help you out.
    I just recently updated to the latest firmware but it's still happening. I actually thought the update would have fixed it so that's why I held off asking this question until I updated it. What version are you on?

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    Click here to enlarge Originally Posted by E90Company Click here to enlarge
    What you said is exactly what i'm experiencing



    I just recently updated to the latest firmware but it's still happening. I actually thought the update would have fixed it so that's why I held off asking this question until I updated it. What version are you on?
    Im on the latest 8/21.. Try messing with the lagfix maybe? But def contact Terry and get some logs in.
    ///M5 LCI
    "It's like the F10 is the 911 Turbo to the E60's GT3" -Pistonheads (M5 feature)

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    Click here to enlarge Originally Posted by 5soko Click here to enlarge
    Im on the latest 8/21.. Try messing with the lagfix maybe? But def contact Terry and get some logs in.
    Yea, I'm going to log for sure. Thanks

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    Click here to enlarge Originally Posted by E90Company Click here to enlarge
    Yea, I'm going to log for sure. Thanks
    sorry to bump an old thread, but did you guys figure out the issue? I really have to get around to running the wire to my glove compartment, I need that special T8 screw driver or w.e it is, blah

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    FWIW, not sure if its the same issue but I've literally, over the last few days, dealt with something similar on a number of cars (@VNeBLOB42, @blisstik, @enrita, @marv85, and a couple other cars) and managed to fix it entirely and people have reported butter smooth stock like performance after the fix...the issue was reported as slight jerking while cruising in the say 2k rpm range and slight touching of the accelerator pedal as if the car would want to accelerate then back off sporadically...WOT was always no problem, just part throttle...
    Click here to enlarge

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    Click here to enlarge Originally Posted by dzenno@ProTUNING Freaks Click here to enlarge
    FWIW, not sure if its the same issue but I've literally, over the last few days, dealt with something similar on a number of cars (@VNeBLOB42 , @blisstik , @enrita , @marv85 , and a couple other cars) and managed to fix it entirely and people have reported butter smooth stock like performance after the fix...the issue was reported as slight jerking while cruising in the say 2k rpm range and slight touching of the accelerator pedal as if the car would want to accelerate then back off sporadically...WOT was always no problem, just part throttle...
    Yes that sounds like the issue. What did you do?? Can I fix it with the JB4?

  24. #24
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    I'm not sure if it can be fixed on the piggy side to be honest. Its calibration of part throttle management that needs refinement basically especially as you up boost/timing in the tune.
    Click here to enlarge

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    in for where this goes.. same issues for me usually limited to the first few minutes of driving after start up. and i do have the most recent firmware as a few others have stated.

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