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    Boost Req. drops suddenly during WOT

    Hey,

    sometimes i get a strange drop in power during WOT pulls in lower gears. (it's not DTC!) I can feel it and it's also clearly visible in the logs, that Boost Setpoint Factor, Boost Req. (and accordingly Boost Mean) go down in the range at about 4000 - 4500 rpm and back up again afterwards. I've marked the region in the datazap log, where Boost Req. drops nearly 200mbar (or 3 psi).

    http://datazap.me/u/rayban81/boost-r...7-8&mark=19-26

    Any ideas, what causes this behaviour?

    Best,
    Clemens
    335i N54 E91, 6MT, DP, performance exhaust, COBB

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    Are you running an OTS , ProTune or SelfTune map ?

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    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    Are you running an OTS , ProTune or SelfTune map ?
    It's basically an Stage 2 Sport Map, remapped by myself for better driveability, get rid of TC's and so on. I've tweaked WGDC Base, WGDC Spool, WGDC Adder, WGDC D-Factor, Load Target, Ign. Base (copied from Aggr.), Throttle threshold, Throttle Angle Aggr. in Overload and Driver Request map.

    It seems like that behaviour only occurs sometimes in "dynamic" situations like blip downshift, accelerating in lower gears and so on. If I do a steady pull in 4th or 5th gear boost is flat in that region.
    335i N54 E91, 6MT, DP, performance exhaust, COBB

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    Click here to enlarge Originally Posted by RayBan81 Click here to enlarge
    It's basically an Stage 2 Sport Map, remapped by myself for better driveability, get rid of TC's and so on. I've tweaked WGDC Base, WGDC Spool, WGDC Adder, WGDC D-Factor, Load Target, Ign. Base (copied from Aggr.), Throttle threshold, Throttle Angle Aggr. in Overload and Driver Request map.

    It seems like that behaviour only occurs sometimes in "dynamic" situations like blip downshift, accelerating in lower gears and so on. If I do a steady pull in 4th or 5th gear boost is flat in that region.
    Mind posting screen shots of your WGDC base and WGDC adder ?

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    np

    Click here to enlargeClick here to enlarge
    335i N54 E91, 6MT, DP, performance exhaust, COBB

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    I am not an expert or a pro, but it looks like you are "choking" the cars performance. Your maximizing your Boost Limit Multiplier but yet making things claustrophobic to perform at its optimal level obviously by trying to control overshoots

    I only have experience tuning the 335is, and some "methods" dont apply very well to the older N54s.

    Start over with whatever OTS map that matches your Mods and fuel usage.
    Revert the OTS WGDC base table back to the stock WGDC base table.
    Lower the Boost Limit Multiplier to 2.300 straight accross then gradually raise the top end "first" till you start to overshoot then back off of it. Raise/Decrease the other cell ranges in the same way. When your done you should have something that looks like this in the ATR graph:

    Click here to enlarge

    Try to "minimize" as much as spossible the overshoots that will lead to trottle closures. take your time and of course with every cell increase/degcrease you have to run logs.

    The key here is to avoid touching the WGDC base table. This should get you a starter or base map.

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    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    I am not an expert or a pro, but it looks like you are "choking" the cars performance. Your maximizing your Boost Limit Multiplier but yet making things claustrophobic to perform at its optimal level obviously by trying to control overshoots

    I only have experience tuning the 335is, and some "methods" dont apply very well to the older N54s.

    Start over with whatever OTS map that matches your Mods and fuel usage.
    Revert the OTS WGDC base table back to the stock WGDC base table.
    Lower the Boost Limit Multiplier to 2.300 straight accross then gradually raise the top end "first" till you start to overshoot then back off of it. Raise/Decrease the other cell ranges in the same way. When your done you should have something that looks like this in the ATR graph:

    Click here to enlarge

    Try to "minimize" as much as spossible the overshoots that will lead to trottle closures. take your time and of course with every cell increase/degcrease you have to run logs.

    The key here is to avoid touching the WGDC base table. This should get you a starter or base map.
    Hmm...i have put days of work in this map(s) and the car performs very well with it. (except from that strange behaviour) I'll give your method a try, but I can't see the point where my tweak of the base table relates to that behaviour. As you can see the WGDC base map is tweaked everywhere. This is because my car tended to overshoot everywhere. In every rev range, on part throttle, full throttle..... The WGDC Adder is only upped in the 1200kg/h cell to compensate the upper rev range, when the base table reaches it's outer cell.

    On the other side, the N54 is a complicated machine...some things take time to understand, even if someone knows the basics. Anyway, thank you very much for your input! I'll give it a try and report!

    What do call an older N54? Based on MY or on mileage?
    335i N54 E91, 6MT, DP, performance exhaust, COBB

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    Click here to enlarge Originally Posted by RayBan81 Click here to enlarge

    What do call an older N54? Based on MY or on mileage?
    Tehcnically non IS/1M n54 cars. The P Factor tuning on the IS/1M model is completely different to their N54 predecessors. There are certain tables that are active on the IS/1M that are null on the non IS/1M N54 cars

    So non IS/1M tuning "methods" work well on the IS/1M, but IS/1M tuning that use all the tables will not work well on non IS/1M n54 cars from my expereince.

    I am surpised all the tuning gurus we have around here have not pitched in to give some suggestions...sigh Click here to enlarge

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    Am actually getting the same issues with my DCT equipped M sport model. Have recently switched from Jb4 to protune and the difference in part throttle smoothness and response is remarkable but have the similar problem of nose diving at 4000 rpms but as soon as it pasts that car pulls like a bat out of hell. Is there something we have to be careful when tuning DCT equipped cars especially on the WGDC tables?

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    Click here to enlarge Originally Posted by DevourS65 Click here to enlarge
    Am actually getting the same issues with my DCT equipped M sport model. Have recently switched from Jb4 to protune and the difference in part throttle smoothness and response is remarkable but have the similar problem of nose diving at 4000 rpms but as soon as it pasts that car pulls like a bat out of hell. Is there something we have to be careful when tuning DCT equipped cars especially on the WGDC tables?
    mine is a 6-speed manual, so the problem shouldn't be related to DCT...
    335i N54 E91, 6MT, DP, performance exhaust, COBB

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    Click here to enlarge Originally Posted by RayBan81 Click here to enlarge
    mine is a 6-speed manual, so the problem shouldn't be related to DCT...
    Noted but BuraQ seems to mention the otherwise...

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    Click here to enlarge Originally Posted by DevourS65 Click here to enlarge
    Noted but BuraQ seems to mention the otherwise...
    It has nothing to do with transmission type and or table reference to it. I have never had this happen on my car even when running the PTF E50 map.

    There is a night and day difference with the OPs tables and mine though

    You said your getting this issue on a ProTune, who Protuned your car ?

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    I haven't had much time to test in the last 2 days but at first sight BuraQ's method seems to work. No (noticeable) closures so far in daily driving and the car feels much better now overall. I'm really surprised....

    Now I'm wondering what the Boost Limit Multiplier table really effects? Is it a limitation of Boost Setpoint Factor? And if it is, why does it also seems to cure my light load part throttle closures?
    335i N54 E91, 6MT, DP, performance exhaust, COBB

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    1 out of 1 members liked this post. Reputation: Yes | No
    Click here to enlarge Originally Posted by RayBan81 Click here to enlarge
    Hey,

    sometimes i get a strange drop in power during WOT pulls in lower gears. (it's not DTC!) I can feel it and it's also clearly visible in the logs, that Boost Setpoint Factor, Boost Req. (and accordingly Boost Mean) go down in the range at about 4000 - 4500 rpm and back up again afterwards. I've marked the region in the datazap log, where Boost Req. drops nearly 200mbar (or 3 psi).

    http://datazap.me/u/rayban81/boost-r...7-8&mark=19-26

    Any ideas, what causes this behaviour?

    Best,
    Clemens
    This tend to happen on fresh flashed maps. Let it adapt and it will clear out.
    Cobb E30 / DCI / VRSF Downpipes / VRSF 7" Intercooler / Walbro LPFP / E85

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    Click here to enlarge Originally Posted by RayBan81 Click here to enlarge
    I haven't had much time to test in the last 2 days but at first sight BuraQ's method seems to work. No (noticeable) closures so far in daily driving and the car feels much better now overall. I'm really surprised....

    Now I'm wondering what the Boost Limit Multiplier table really effects? Is it a limitation of Boost Setpoint Factor? And if it is, why does it also seems to cure my light load part throttle closures?

    I have always understood it to be a Setpoint for boost (as reflected in logs) but calibrations will differ depending on what sea level (SL) you are at. It doesnt play a role by itself as it is also factored in with other calculations for load.

    So in other words it is a boost SP limitation for load, IMO. For example 190 LD + Baro(*SL) + 2.3 SP = 17 PSI, but 170 LD + Baro(*SL) + 2.3 SP may not = 17 PSI - which can make the system unbalanced hence overshooting load target. Balancing out the system first should be a priority without having to touch the WGDC Base table

    When all done you will see the WGDC Base table is a last resort as there are other tables to control boost and "minor" throttle closures.

    I used the word "choke" as you were telling the system to target a SP but yet limiting it in another place will cause part throttle closures IMO instead of it being proportioned.

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    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    It has nothing to do with transmission type and or table reference to it. I have never had this happen on my car even when running the PTF E50 map.

    There is a night and day difference with the OPs tables and mine though

    You said your getting this issue on a ProTune, who Protuned your car ?
    a friend of mine is a local cobb dealer that normally tunes GTR's but have never tuned bmw's. just wanted to gather more information for him as he has tweaked the WGDC table thinking that it should help with the spool.

    Maybe you can chime in here for me to tell him what not to do. Funny thing is that he managed to run boost up to 19 psi but I suspect that glitch at 4000 rpm visile on dyno is throttle closure. You mentioned the WGDC table need not be touched at all?

    thx in advance.

    dixon

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    Click here to enlarge Originally Posted by DevourS65 Click here to enlarge
    a friend of mine is a local cobb dealer that normally tunes GTR's but have never tuned bmw's. just wanted to gather more information for him as he has tweaked the WGDC table thinking that it should help with the spool.

    Maybe you can chime in here for me to tell him what not to do. Funny thing is that he managed to run boost up to 19 psi but I suspect that glitch at 4000 rpm visile on dyno is throttle closure. You mentioned the WGDC table need not be touched at all?

    thx in advance.

    dixon

    WGDC base table should be "last resort".... after, blancing out the system to reduce as much overshoots and major throttle closures with the BLM table "IF" your using Cobb's OTS map as a base start.

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    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    WGDC base table should be "last resort".... after, blancing out the system to reduce as much overshoots and major throttle closures with the BLM table "IF" your using Cobb's OTS map as a base start.
    @BuraQ pls

    do u miss me yet
    - Proven Power Tampa built 6466 ST -
    - N54 6AT WR 711whp 637wtq-
    -N54 WR 1/4mile trap: 133.57mph- -

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    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    WGDC base table should be "last resort".... after, blancing out the system to reduce as much overshoots and major throttle closures with the BLM table "IF" your using Cobb's OTS map as a base start.
    I took a log today on the highway with an OTS aggressive stage 2 map and lowered BLM, but the behaviour was exactly the same as with my own modified map + some serious TC's.

    http://datazap.me/u/rayban81/3rd-gea...=0&data=3-8-10

    One finding in that:

    You will get driveability problems on lower part throttle, if you set the WGDC Base map too low, because PID kicks in often an aggravates things. I drove my own map for many weeks and it was good to get a reference again with the stock Base table.

    However...boost req. decreases but load is stable...doesn't make any sense to me...
    335i N54 E91, 6MT, DP, performance exhaust, COBB

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    Click here to enlarge Originally Posted by RayBan81 Click here to enlarge
    I took a log today on the highway with an OTS aggressive stage 2 map and lowered BLM, but the behaviour was exactly the same as with my own modified map + some serious TC's.

    http://datazap.me/u/rayban81/3rd-gea...=0&data=3-8-10

    One finding in that:

    You will get driveability problems on lower part throttle, if you set the WGDC Base map too low, because PID kicks in often an aggravates things. I drove my own map for many weeks and it was good to get a reference again with the stock Base table.

    However...boost req. decreases but load is stable...doesn't make any sense to me...
    There are couple of things I am seeing not right here. Did you lower the load for the OTS map ? The load request looks lower than what the Cobb OTS load table is set for, unless I am missing something ?

    Load request should be targeting 190 on stage 2+ aggressive. Load Req on that log is target about 180. Load req should not be that far off from the load your trying to target

    Load needs to be raised. This is the load table I am seeing for both IS and non IS for OTS stage 2+ aggressive

    Click here to enlarge

    If your table is lower than that, then, thats a start for you. There are two tables, one for MT and one for AT, change both to be identically the same.

    Second thing, your shifting at almost red line, I am not sure why you would be doing that on this car since after 6k RPMs everthing starts to go down hill on stock turbos. Its like trying to catch breath again after the air has been exhausting in your lungs. Next time try shifting before 6300 RPMs

    Most of your throttle closures are due to "load overshooting" the load req, raising load from 1550k-6k RPM range on the load table will deminish most of this and you should see less trottle closures (TC)

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    Click here to enlarge Originally Posted by Ak335i Click here to enlarge
    @BuraQ pls

    do u miss me yet
    Talk about strangers, of coruse I do, we need to have a meet soon, waiting on you to get things cleared up on your end

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    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    Talk about strangers, of coruse I do, we need to have a meet soon, waiting on you to get things cleared up on your end
    ill be home 4/11
    i have my car its running perfect and strong on wastegate (just keeping it tame until the tranny swap) but yea
    we should do some rolls, me u and preezy
    - Proven Power Tampa built 6466 ST -
    - N54 6AT WR 711whp 637wtq-
    -N54 WR 1/4mile trap: 133.57mph- -

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    @Bura: I'm driving the standard stage 2 aggr., not the one for FMIC cars. All tables are standard, except the BLM

    But generally: Raising load to the limits of the turbos will mask the overshoot problem, not cure it. As i said: My own WGDC Base map cures the overshoots in 95% of all cases, but thats not the answer to the swinging boost request from the ecu.
    335i N54 E91, 6MT, DP, performance exhaust, COBB

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    Click here to enlarge Originally Posted by RayBan81 Click here to enlarge
    @Bura: I'm driving the standard stage 2 aggr., not the one for FMIC cars. All tables are standard, except the BLM

    But generally: Raising load to the limits of the turbos will mask the overshoot problem, not cure it. As i said: My own WGDC Base map cures the overshoots in 95% of all cases, but thats not the answer to the swinging boost request from the ecu.
    Then I dont know what else to say, other than to go with the flow, feel out what the car wants not what it needs. What I see is that the car wants Load to be raised. I dont see this as masking the issue. If so, then chopping down the WGDC base like it was before would be considered masking the issue also

    I paid very close attention to how BMW tuned the IS and non IS cars and compaired every single table stock for stock. They did not hack down the WGDC base, they "barely" touched it for increasing boost on a car from 8 PSI to 13.5 PSI, in fact they raised it.

    I think you should approach this more than one way. You already have one map made just make another based on the contrary method and see how the car does.

    Its too early at this point cause the car's performance has not been proportioned yet

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    Sorry, I didn't want to offend you. I do appreciate your help and participation very much! I get your point and sure it doesnt make any sense to raise the Base table to make boost, as the table is a function of Setpoint and Airflow. If you raise load, the ECU will raise the setpoint and you'll reach higher cells in the base table. No need to change anything. In theory no one needs to touch the base table, as long as you are not getting to the axis-limits or as the p3/p4 ratio changes. (which changes when installing downpipes, but obviously not that much, as COBB didn't alter the base table for stage 2 cars)

    Josh@Cobb thinks that my WG's are "overtight" and therefore my Base table needs to be lowered that much. But I didn't find a setup until now, which makes the car run perfectly. It's a headache and a trade off between overshoots and response time. Slight issues remain until now. But that is another problem and in my opinion has nothing to do with the dropping boost request from the ECU. It's just that I'm not able to find ANY reason (in the maps and the logs) why the car first raises boost request after going WOT, then lowers it and afterwards raises it again. It's a miracle for me and I just want to understand, what is going wrong.

    Best,
    C
    335i N54 E91, 6MT, DP, performance exhaust, COBB

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