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J.warasila J.warasila is offline
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Join Date: Aug 2020
Car: 2008 bmw 335i e92
Default jb4 switching to map 4 after mhd bef - 08-18-2020, 05:34 PM

first post! okay so for starters i am a 08 e92 n54 335i with a cp and bov, fmic, bms dual cone intake, recently got a jb4 and i am running map 5 with an e20 mixture. just got mhd and did a back end flash today. I was driving after i installed the bef and i notcied that on a 3rd gear pull i got a cel, misfire cyl6, brought the car home turned it off and back on and it disappeared. brought the car back out to try to get it to replicate which it didn't, but 5300 rpms into 3rd gear i got the flashes from the hazards and it switched me to map 4. turned around drove a half mile switched back to map 5 and data logged. i'm very new to tuning and I've been studying up on how to read these graphs but i figured it'd be better to show you guys and learn that way. thanks so much.
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J.warasila J.warasila is offline
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Join Date: Aug 2020
Car: 2008 bmw 335i e92
Default 08-18-2020, 06:19 PM

Also could it be that i have a boost leak on my bov because i have too weak of a spring? its a tial black bov with an 11 pound spring. If i was creating boost pressures of 15-17 would that open the valve and be causing a leaning issue? which is what im assuming is happening.
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e90n54sjs e90n54sjs is offline
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Join Date: Sep 2020
Car: 08 e90
Default 09-16-2020, 05:33 AM

Make sure under menu 4 you have it set to 2. I had the same issue after a bef. factory jb4 setting is 3. menu 4 selection 2 lets the jb4 know you have a bef.
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dmckmc dmckmc is offline
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Join Date: Oct 2017
Car: E60 535i
Default 09-17-2020, 04:33 PM

First thing is first: The purpose of the spring in a BOV IS NOT to hold your BOV closed under boost pressure!

All BOVs have a reference line coming into the top of the BOV from your post-throttle body intake manifold. Under high boost, the force holding the BOV closed is BOOST! The pressure coming through the reference line is equal to the pressure under the BOV piston. Therefore a VERY mild spring will hold it shut just fine under these conditions.

Rather, the purpose of the spring in a BOV is to hold the BOV closed when your throttle plate is closed, IE during idle and deceleration conditions.

Therefore, your goal when selecting a BOV spring and adjusting the BOV should NOT be to select a spring based on your boost level; that makes no sense. Your goal is to get the BOV to stay CLOSED during high intake manifold vacuum/closed throttle plate conditions, using the very smallest amount of spring energy possible. Using less spring energy will allow the BOV to snap open as rapidly as possible when pressure release is necessary.

Second: where are your logs? Really can offer little support without them, it would be pure speculation. Also best to post logs and support questions in the N54 Support & Log Review sub forum.


Last edited by dmckmc; 09-17-2020 at 04:58 PM..
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