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Reload this Page Any manual trans JB4 owners having issues with bog when shifting really fast?
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Nugs Nugs is offline
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Posts: 393
Join Date: Apr 2013
Car: 2011 135i
Default 12-10-2018, 11:25 PM

Originally Posted by Terry @ BMS
If so we've got something new for you to test.

We made an interesting discovery for torque limiter based shift bog (a common issue when shifting fast) that we believe will lead to dramatically improve manual transmission shift response. Essentially, if the DME does not see the clutch press in during a shift, it appears not to trigger any torque limiters. We are getting scary hard shifts in our development cars. Completely awesome.

We plan to use the JB4 to dynamically shield the clutch information from the DME. But before we fully develop that we need a few customers who have bad MT shift lag to do a little experiment for us. You'll load special JB4 firmware, pull the clutch wire out in the DME connector, set FutureUseD bit4 on letting the JB4 know to enable the new logic, and log a few fast shifts, so we can ensure this solution seems likely to work in all applications. Once we have that data we'll get to work on further refining the logic.

To test it out:

1) Load the attached firmware (note both twin turbo and single turbo firmware attached).
2) Set FutureUseD Bit 4 on and save settings. It's called "Aquamist WMI algorithm" in firmware descriptions but that logic is now part of the WMI flow scaling.
3) Unplug the clutch wire as shown in this photo. Gray connector #18. It can just tuck out the way.
4) Enjoy must better fast shifts!

Side Effects:

1) As implemented, the JB4 is not currently reading gear, so boost by gear has been changed to boost by speed. Where 1st is < 40mph, 2nd is 60mph, and 3rd is 86mph. We've got some ideas to correct this back to true boost by gear we'll need to flush out.
2) With the DME no longer seeing the clutch position cruise control doesn't work.
3) The clutch safety start logic appears fully functional. Test and let me know if you find otherwise!
4) You'll have a shadow code stored for clutch pedal signal not active. Just ignore it.
Has anyone tested this or similar on a B58 car?
I would love to get rid of the shift bog and rev hang.
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chantura chantura is offline
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Posts: 8
Join Date: Jan 2018
Car: BMW E82 135
Default 07-16-2019, 11:47 PM

Hi, guys so i had next issue:

i have activated 2 step rev limiter and my lag is huge now... before that i haven't it almost but now i have. so i'm interested does it related to each other? i'm changing gears without take off feet from the acceleration, so after 2 step limiter its throwing me in 4 map if i'm doing like that but if im changing gear with take off feet it does not.... before that i wasn't taking feet off from acceleration and it was OK. i will take logs and will post it... i don't have back end flash but much faster than MHD stage 2+.... also in my country (Georgia) everybody is taking out JB4 and making custom tune or MHD...
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E90-STACKS E90-STACKS is offline
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Join Date: Oct 2019
Car: E90 n54 335
Angry Im experiencing this now not sure for how long because at one point it worked - 10-12-2019, 08:56 AM

Originally Posted by Terry @ BMS
The specific torque limiter we've found a work around rears it's ugly head most often when trying to shift really fast, causing RPM to spike up as you press the clutch pedal in, and lasts around a second or so post shift.
Im trying to figure out wheres the problem coming from is it mechanical or software related, When I attempt a nls the car rpm rises and slips clutch into next gear... Cdv already deleted
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