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  1. #1
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    2 out of 2 members liked this post. Yes Reputation No

    Weird stepwise acceleration (Log Files inside) Nedd help!

    So,
    I have a annoying problem with my N54.

    Everytime I accelerate with WOT from lower RPM's (everything under 3000RPM) it feels like the handbrake is pulled and then released about a second after I push the pedal to the floor. In the Moment that second of hesitation ends, when the car starts accelerating as it should, I can feel a short shrug.
    Another thing I recognized is, that the car keeps accelerating for a second, even if i lift the foot quick of the gas.
    Feels like something's not acting fast enough.
    Since I'm knew to the N54 I did some datalogging and looking forward for you to help me.

    I really want a pro tune, but I need to be sure the car is allright before Click here to enlarge

    Some Facts that might be interesting:
    135i '08, new Turbos, new plugs, inlet valves cleaned, 4 injectors and HPFP replaced some time ago by BMW, cleaned and switched the vanos solenoids today (no major difference).
    I'm running the Wagner FMIC, catless DP's, Performance Exhaust and Map is COBB Stage2+ v402 on 102Octane (I live in Germany).

    Sorry, If my english is partly hard to understand. I hope you get the plot.

    Unformated Datalogs here, some Graphs attached:
    ://dfiles.eu/files/b1vpxq5q2
    ://dfiles.eu/files/epizirojp
    ://dfiles.eu/files/wnmj1i5hk

    Since I'm not alloed to post links, you need to put the http in front.
    Attached Images Attached Images    

  2. #2
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    I don't see anything jumping out at me in the logs suggesting anything is wrong. It could just be that you're asking for to much from to low of an RPM. The small turbos build boost fast but it still takes some revs for it to start pulling. Also, the felling you describe of the throttle not reacting fast enough when letting off is normal... electronic throttle control isn't exactly all the mfgs claim it to be when it comes to throttle response.
    Click here to enlarge
    MOTIV750, MOTIV P-1000 PI, MOTIV/FUEL-IT! low pressure fuel system, AEM EMS/COBB AP, Aquamist HFS-3, ETS FMIC, SPEC stage 3+ clutch/SS flywheel, BC Racing coilovers and VMR wheels wrapped in Hankook RS3s.

  3. #3
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    What bothers me isn't the time the turbos need to spool. I can feel the boost build up, then the car is holding back shortly until a mechanical shrug goes through the car and it pushes forward.
    The other problem with the car accelerating while letting of gas can't be normal either. It' like someones pushing the gas to the floor shortly immediatly after I let off. Probably these thingshappen in a to small period of time, so it wasn't captured in the log files.

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    1 out of 1 members liked this post. Yes Reputation No
    I'm pretty sure I have the same problem. Very similar setup and running the same map.

    For me it's most noticeable at 4,000rpm, so I wouldn't say it's due to low RPM. I saw nothing out of ordinary in my logs, unfortunately.

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    I'm wondering about vanos control for the stepwise feeling, which I have experienced as well. As for the continuing to accellerate, no idea there.

  6. #6
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    @ty royaqle , did you try to run another map (like stage1 sport for instance) and see if you still have the problem. A couple of people reported the acceleration after letting of the throttle. Hell I had it but it was solved a long time ago with COBB.

    the other thing that we might want to see, is your actual timing. Post your actual timing on all cylinders. That could explain why the car has no power and suddenly wakes up...
    SOLD --'07 E90 335i, PTF COBB E50, HFS4, ER CP, ETS 7", AA DP, Vishnu Exhaust, DCI, ACT, Nitto Nt555

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    I changed to Sport yesterday and it feels much more comfortable. But after some runs it still has the stepwise acceleration problem. It's is not that hard anymore, but you can feel the boost stuck and then going up. I marked it in red on one graph where it's stuck. Is it possible, that the wastegateadjustment of my new turbos ist too tight. Because when i compare my logs i can see overshoots in the problemtaic RPM-Range. Probaly the ECU recognizes that and holds back boost for some time? Possible?
    Timing is perfect, no time correction on none of the cylinders.

    Following graphs were made running the 2+ Sport map about 10miles after flashing, so it isn't really adapted.

    ://dfiles.eu/files/zktcj8dz1
    ://dfiles.eu/files/rvhtpaxrh

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    Click here to enlarge Originally Posted by Ty Royaqle Click here to enlarge
    I changed to Sport yesterday and it feels much more comfortable. But after some runs it still has the stepwise acceleration problem. It's is not that hard anymore, but you can feel the boost stuck and then going up. I marked it in red on one graph where it's stuck. Is it possible, that the wastegateadjustment of my new turbos ist too tight. Because when i compare my logs i can see overshoots in the problemtaic RPM-Range. Probaly the ECU recognizes that and holds back boost for some time? Possible?
    Timing is perfect, no time correction on none of the cylinders.


    Following graphs were made running the 2+ Sport map about 10miles after flashing, so it isn't really adapted.

    ://dfiles.eu/files/zktcj8dz1
    ://dfiles.eu/files/rvhtpaxrh
    it's good that there is no timing correction but you also need to look at actual timing. sometimes the CPU requests less timing and that can feel like a step in power. Post the CSV from the run where you felt that
    SOLD --'07 E90 335i, PTF COBB E50, HFS4, ER CP, ETS 7", AA DP, Vishnu Exhaust, DCI, ACT, Nitto Nt555

    '10 E92 335i M, 6MT COBB v3, ER IC, ER CP, VRSF DP, Fuel-it st2
    installing soon: Mfactory LSD, , powerflex subrframe bushings

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    I have a PROcede and actually have a very similar problem, but is not as consistent. If I drive under low loads for a while, then suddenly apply a lot (70%+) of throttle in a high gear, I feel a thud, as if the engine had an immediate hesitation or switched maps real quickly. The passengers never notice, but I notice it as the driver. I can live with it if it isn't causing any harm to the car.

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    Click here to enlarge Originally Posted by Ty Royaqle Click here to enlarge
    The other problem with the car accelerating while letting of gas can't be normal either. It' like someones pushing the gas to the floor shortly immediatly after I let off
    That sounds to me more like the DV's are sticking, maybe due to a blockage in the vacuum lines somewhere.
    They should open immediately when you let off the throttle. If the inlet remains pressurized it feels just like yo describe.
    There are two theories to arguing with women. Neither one works

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    I'm having the same *exact* issues you're describing. Both occur together - there's a slight shrug once you go WOT, then a swift kick as it seems to slip back into a normal mode. Letting off WOT, I get basically two pressure blow-offs / diversions which seem to indicate one of the DV's is sticking.

    I'm thinking this is a stock DV issue, leaking then sealing at first, and likewise sticking shut then opening late once off WOT.

    Note - I didn't feel this all winter on a Stg2+ sport OTS map, but once I went back on an E40 map with a little more boost, the issue started immediately. I guess I'm 85% DV issue, 10% tune issue, 5% no clue at all.

  12. #12
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    Time for an open/inspect/clean/reassemble of the DV's.

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    Chenged the DV's. Feeld quite allright now with the Stage 2+ Sport OTS map! Will keep you up to date!

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    Good stuff! One of my DV's was loose in the collar (the little grey twist lock was in the open position) and I finally popped the sucker out like a shotgun slug between shifts. Not sure if the guys at my local BMW forgot to tighten it back down after playing with it last week.

    OP, did you go with OEM's or forge/aftermarket?

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    I've had some issues with my Forge DV's; I believe they may have some unfavorable tolerances between the piston and the valve body. The DV's not functioning properly definitely causes a very noticeable issue.

  16. #16
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    Addition to the above; car was acting cranky tonight, and I noticed that after I got off throttle, heard one DV release... then a split second later the other one (quieter). I'll be pulling them apart tomorrow (again). Sent in a request to the vendor I purchased them from that they put in a word for me with Forge, perhaps I can get at least a rebuild kit for no dollars, since they're <2 mos old.

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    Click here to enlarge Originally Posted by r0nd3L Click here to enlarge
    I'm pretty sure I have the same problem. Very similar setup and running the same map.

    For me it's most noticeable at 4,000rpm, so I wouldn't say it's due to low RPM. I saw nothing out of ordinary in my logs, unfortunately.
    Did it do it when stock? Have you tried other tunes?

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    Click here to enlarge Originally Posted by SCGT Click here to enlarge
    Addition to the above; car was acting cranky tonight, and I noticed that after I got off throttle, heard one DV release... then a split second later the other one (quieter). I'll be pulling them apart tomorrow (again). Sent in a request to the vendor I purchased them from that they put in a word for me with Forge, perhaps I can get at least a rebuild kit for no dollars, since they're <2 mos old.
    I have similar double blow off with HKS SSQV. I wonder if I should try instlaling stock charge pipe with stock DVs and give that a shot.

    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Did it do it when stock? Have you tried other tunes?
    I bought the car modded, so not sure. I should try different map, just been lazy.

  19. #19
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    Click here to enlarge Originally Posted by r0nd3L Click here to enlarge
    I should try different map, just been lazy.
    Um ya, you should.

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    Same issue. Cobb Stage 2+ Drive map and running Forge DVs.

    I thought it was a DV also so I took them apart, cleaned them, and added some Mobil 1 grease. But I still have the issue.
    I was thinking about going back to the stock DVs to see what happens.

    Second thought was VANOS. Mine are old and have over 90K miles on them. Haven't replaced them though.

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    Click here to enlarge Originally Posted by stangorang Click here to enlarge
    Same issue. Cobb Stage 2+ Drive map and running Forge DVs.

    I thought it was a DV also so I took them apart, cleaned them, and added some Mobil 1 grease. But I still have the issue.
    I was thinking about going back to the stock DVs to see what happens.

    Second thought was VANOS. Mine are old and have over 90K miles on them. Haven't replaced them though.
    When I dissassemble/clean/reassemble the Forge DV's the problem seems to be absolved for a few days. I contacted Forge and they're sending me a rebuild kit in the event that something is out of tolerance. I'll keep this thread updated if that ends up being the cause.

    I also was suspicious of the VANOS solenoids. That'll be next on the list to at least remove/clean/reinstall, which isn't a bad idea with 80k on the odometer.

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    Click here to enlarge Originally Posted by r0nd3L Click here to enlarge
    I have similar double blow off with HKS SSQV. I wonder if I should try instlaling stock charge pipe with stock DVs and give that a shot.

    The double blow off is due to the throttle plate angle staying open momentarily between shifts. I've seen it in logs where boost will equalize between shifts long enough to give you the "double" sound you speak of.

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    Click here to enlarge Originally Posted by Tzu Click here to enlarge
    The double blow off is due to the throttle plate angle staying open momentarily between shifts. I've seen it in logs where boost will equalize between shifts long enough to give you the "double" sound you speak of.
    That makes complete sense. I thought it will have something to do with throttle body. I will run some logs once it stops raining here (if it ever will). Would you say it's pretty normal?

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    Yea it's normal. Probably for shift softening. It's only 1/10th of a second or so.

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    Did a log last night, not 100% sure I captured the event, but I logged vanos and it was pretty close to dead on (req/act).

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