Inconsistent boost - N54Tech.com

blackhat75 · **Inconsistent boost -** 07-05-2020, 03:56 PM

Hey guys,
I'm having an issue with over boosting. It seems to happen on any map. I have the PS2, race *****, intake/exhst, bms PI direct port meth/metal manifold, the works. I have set the jb4 to 1 under N20 sensor to achive higher boost levels. Map 1 should be 16psi. Map 2 should be 19psi. Sometimes, I'll get 20+ psi on map 1, then, after a pull or two, it comes back down to 16-17psi. Even worse, map 2 shoots up to 22-25psi! Luckily, I recently put a bunch of 105 octane in for safety. I have the JB4 boost limit set to 20psi yet it just ignores it. I'm still trying to determine whether it's a mechanical issue or software issue. Maybe a bad or cracked wastegate hose? Is there a setting in the JB4 I missed that would cause it to behave this way?

Terry @ BMS · 07-05-2020, 04:45 PM

Post up a JB4 log if you need tuning advice.

blackhat75 · 07-05-2020, 08:40 PM

Oops! Sorry T
Here's a combo log from yesterday heading home from the show. A mix of low speed and high speed pulls. I suppose this should be moved to the support sub-forum.

Terry @ BMS · 07-06-2020, 09:48 AM

Enter the default hybrid N55 turbo settings, lower FF to 60, grab another log.

blackhat75 · 07-10-2020, 01:03 PM

After disabling FF RPM gain and setting FF to 60, I tried to make some 3rd gear pulls on the way to work n back. These pulls were the opposite of what I was experiencing before. I'm not reaching the 16psi map1 level now. Take a look and let me know if you see anything I can try. I'm sure it's something simple I'm just overlooking. The car's running great regardless. You can feel when a car is happy, ya know?

Dave @ BMS/Fuel-It! · 07-10-2020, 01:21 PM

Doesn’t look like you entered our default duty bias settings.

Do that, & relog

blackhat75 · 07-11-2020, 10:02 AM

Tried uploading log(s) yesterday but the whole post disappeared

. Try this again.
-Pull 1: decent
-Pull 2: overboost, shut it down early
-Pull 3: overboost again, switched to map 4 safety
-Pull 4: map 4 still active, corrected
-Pull 5: junk
-Pull 6: decent
-Pull 7: 3-4 great
-Pull 8: 3-4 decent

Dave @ BMS/Fuel-It! · 07-11-2020, 01:17 PM

Up your PID to 25 (default)

Not uncommon after changes it takes 3-4 WOT pulls to adapt / learn.

How does the car pull now?

blackhat75 · 07-13-2020, 07:21 PM

Hey Dave,
Thanks for your continued help. I really appreciate it. Here's todays log(s) after setting PID=25. PSI was a little over but pull after pull, it felt really consistent. The 3-->4 shifts are amazing. First time I double checked my seatbelt was on and tight

Dave @ BMS/Fuel-It! · 07-14-2020, 04:44 AM

Looks very clean to me. Fun when everything starts to fall in line

MarcosFT · **Low boost after wheels spin -** 07-14-2020, 01:34 PM

Hi Terry...I have a PWG 335i F30 (big turbo, PI, MHD flashed, JB4 running on map 6). The boost is always near to target, the only exception is after wheels spin and throttle body closes. At this moment, the boost drop under target and cannot rise again, even after a gear change. It only happens when the wheels spin. Can you help me?

Terry @ BMS · 07-14-2020, 03:24 PM

I'd suggest reconnecting the diode and going back to integrated firmware, or grabbing a new V2 JB4 control board that will have the diode installed. The new int firmware provides better boost control and performance overall than the ISO you're running.

blackhat75 · 07-14-2020, 05:55 PM

Quote:

Originally Posted by Dave @ BMS/Fuel-It!

Looks very clean to me. Fun when everything starts to fall in line

Agreed. Is there a way to reduce the initial boost value at the beginning of every pull though? That's been the actual problem from the beginning. How can I level off or stabilize the boost? Can I adjust the duty bias per rpm?

Dave @ BMS/Fuel-It! · 07-15-2020, 01:15 PM

Yeah you can tweak duty bias as you see fit.

blackhat75 · 09:12 PM

Quote:

Originally Posted by Dave @ BMS/Fuel-It!

Yeah you can tweak duty bias as you see fit.

Hey Dave, so if I wanted to lower my target psi at a particular rpm, I'd lower my Dbias in increments at that rpm range, right? Or would there be a more global value to change to effect all rpm's together?

Edit: I'm re-reading the very first post by Terry in "JB4 Duty Bias & FF Tuning Info" in the N54 section. Is it safe to assume the details found there regarding JB4 functions will be the same for the N55?

Dave @ BMS/Fuel-It! · 07-16-2020, 08:03 AM

Quote:

Originally Posted by blackhat75

Hey Dave, so if I wanted to lower my target psi at a particular rpm, I'd lower my Dbias in increments at that rpm range, right? Or would there be a more global value to change to effect all rpm's together?

Edit: I'm re-reading the very first post by Terry in "JB4 Duty Bias & FF Tuning Info" in the N54 section. Is it safe to assume the details found there regarding JB4 functions will be the same for the N55?

Correct

I can help you as well... what were you wanting to change?

MarcosFT · 07-16-2020, 04:31 PM

Terry, I reconnected diode and uploaded integrated firmware and the issue remains...Please, take a look in the new log file...

Dave @ BMS/Fuel-It! · 07-17-2020, 05:49 AM

Quote:

Originally Posted by MarcosFT

Terry, I reconnected diode and uploaded integrated firmware and the issue remains...Please, take a look in the new log file...

Hey Marcos

Can you make your own thread? You are jumping in on another users active post. As courtesy to this member, I’d prefer if we weren’t talking about your car on their stuff.

Thanks