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Русский шпион Русский шпион is offline
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Default JB4 adjustments for N54 DCT cars - 10-24-2017, 08:00 AM

Hi guys.
I have Z4 sdrive35is DCT transmission with JB4.
When I go WOT on speed about 60 miles/hr the car shifts back to 4th, sometimes 3rd gear and when it just starts to pull ( the gears are fully engaged already), suddenly a boost swings occurs , one or two waves 10-18 PSI, car stalls for the moment, then pulls normally with 16 PSI of boost, and upshifts without a problem.
It happens in all JB4 maps, except map 0 (OEM map 8 PSI boost max).
It happens with all driving settings , like sport and sport + with traction off...or just traction off..
It happens when I downshift it manually and then slam my accelerator...
It does not happen if I accelerate, but do not go WOT.
It does not happen when I go WOT on a 1 gear and car does not have to downshift.
So question is... what is it and how it can be fixed?
Custom tune of JB4?
If it is a "traction control" intervention how can I turn it off completely?
Maybe it needs a transmission reprogrammation/tuning to help it handle more powerful engine by not shifting down to 3rd gear from 7th?
��

Last edited by Русский шпион; 10-24-2017 at 12:42 PM.. Reason: more details about the issue.
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Terry @ BMS's Avatar
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Default 10-24-2017, 08:31 AM

Add a JB4 log of the issue and we can look at it, but DCT power on downshifts are always a problem, as the DME is programmed for major boost reduction there to keep engagement smooth.


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Русский шпион Русский шпион is offline
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Default JB4 adjustments. - 10-24-2017, 10:47 AM

This is what I was thinking myself, it is a DME action to adjust power level for the circumstances..I would like to upgrade my turbos to stage 2 (up to 25 PSI) but if I do it the boost swings might be dangerously high on downshifts.
Can I suggest to make an update for JB4 that will enable it to take over the control of DME for this action?
Other suggestion - optional for JB4 complete traction control off.
In any case my car will go in winter hibernation this week - optional for Canada . So I will make a log of the problem sometime next year when it will wake up for the summer fun.
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Default 10-24-2017, 11:33 AM

M3/M4 cars have exactly same models of DCT and up to 18 PSI boost level. I guess their DME and/or transmission computers are adjusted for the power/torque surge on downshifting.
If you need a test car - I am all yours. I can remove my JB4, send it to you for reprogramming and test the results on my car . My Z will sleep in a garage till May 2018 anyway.
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Default 10-24-2017, 11:44 AM

The first step is to capture a JB4 log of what you're feeling so we can base any changes on actual data.


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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 click here for more information on legal requirements related to use of BMS parts.
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Default 10-24-2017, 12:34 PM

OK, will do ASAP. If you will not hear from me in a next two weeks - means I will be able to catch the log next year only.
Thank you Terry.
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Default logs are here - 10-25-2017, 10:15 AM

Hi Terry. Was able to make some pulls today with logs in a different settings (normal traction off, sport, sport+).
One log is on map4 just as a stock comparison .
Others are map 5.
Maps1 and 2 and 6(factory preset values) all do the same thing.
I will be out for a week in a vacation, so would be out of reach.
Thank you for looking.
Attached Files
File Type: csv 171025_1225.csv (14.5 KB, 48 views)
File Type: csv 171025sport_1235.csv (18.8 KB, 28 views)
File Type: csv 171025sport+_1232.csv (35.4 KB, 28 views)
File Type: csv 171025JB4_off_map4_1238.csv (20.4 KB, 28 views)

Last edited by Русский шпион; 10-25-2017 at 02:48 PM..
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Default 04-01-2019, 09:09 AM

Привет, Нашлось решение проблем?


2010 BMW Z4 35IS EUR | DCT | JB4 | AR Design *** |
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Ke93 Ke93 is offline
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Default 05-22-2019, 07:47 PM

Quote:
Originally Posted by Русский шпион
Hi guys.
I have Z4 sdrive35is DCT transmission with JB4.
When I go WOT on speed about 60 miles/hr the car shifts back to 4th, sometimes 3rd gear and when it just starts to pull ( the gears are fully engaged already), suddenly a boost swings occurs , one or two waves 10-18 PSI, car stalls for the moment, then pulls normally with 16 PSI of boost, and upshifts without a problem.
It happens in all JB4 maps, except map 0 (OEM map 8 PSI boost max).
It happens with all driving settings , like sport and sport + with traction off...or just traction off..
It happens when I downshift it manually and then slam my accelerator...
It does not happen if I accelerate, but do not go WOT.
It does not happen when I go WOT on a 1 gear and car does not have to downshift.
So question is... what is it and how it can be fixed?
Custom tune of JB4?
If it is a "traction control" intervention how can I turn it off completely?
Maybe it needs a transmission reprogrammation/tuning to help it handle more powerful engine by not shifting down to 3rd gear from 7th?
��

to my knowledge this is caused by a button on the bottom of your pedal that puts your car in an optimal gear for performance mode. id imagine this setting can be tweaked like the jb4 has the ability to disable this function.
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