Boost reduction using JB4

[Hacksaw907]

For those using the jb4 to reduce boost levels of an ECU tune, what bits do you have enabled? And are you using the map6 boost settings, or the FF/Wastegate values? Or a combination of both?

Been trying to reduce my boost by 4-5 psi on the tune I have, but it's causing some weird behaviour at wot, so just curious what others have done that worked for them.

 

[ChaneRZ]

Bits 0, 5, 6 then JB4 map 6. Set 1500 map6 boost to 0 psi.

 

[Yves998]

Don’t ever think about EWG and ecu tune. Just set 1500 rpm to 0 then all the other valves are reduction.

 

[Hacksaw907]

Don’t ever think about EWG and ecu tune. Just set 1500 rpm to 0 then all the other valves are reduction.

So you start the boost reduction right at 2k? Also, I have EWG cables installed, but I have bit 5 on, which should disable them to my understanding. Have you encountered issues with boost reduction even with bit 5 on?

 

[MFNTRBO]

So you start the boost reduction right at 2k? Also, I have EWG cables installed, but I have bit 5 on, which should disable them to my understanding. Have you encountered issues with boost reduction even with bit 5 on?

I have the same problem. Hit 27 lbs of boost. Ended up installing BMS Back-end flash and my boost doesn't go above 21 now but the BEF tune overrides the Sxth map. Only one map at a time can be run, I've discovered.

 

[rpoffen]

Don’t ever think about EWG and ecu tune. Just set 1500 rpm to 0 then all the other valves are reduction.

If you set 1500 to other than 0, then the rest of the values would be added boost?

 

[Terry@BMS]

Whether or not you want to use EWG to further reduce boost depends on the situation/flash.

 

[Yves998]

If you set 1500 to other than 0, then the rest of the values would be added boost?

Yes.

 

[Hacksaw907]

Sorry for the thread necro, but just a quick update on my efforts to reduce boost. Disclaimer: I'm running a lap3 2.5+ tune, so this may not apply to those running other tunes or a stock ecu.

If you are running EWG wires, reducing the ff/Wastegate Adaption settings from the default 50 values will reduce your boost curve. For me, a value between 30/35 cuts about 3.5 lbs of boost across the range.

If you don't have EWG wires, or want to have more minute control on how much boost is reduced, I found that trying to reduce it with the map 6 boost settings will only work well if bit 6 (high boost flash loaded) is set to Off. If you don't disable bit 6, your car will jerk as it's rapidly cutting boost and not. Granted, this may not be the case for everyone, but I found it was the only way for me to get the map 6 boost reduction values to work smoothly, so this tip is for those who are having issues with it.

 

[ExtremePowerHouse - MIke]

Thank you for your insights.

I would caution against changing the JB4 settings independently. Modifying a single setting might achieve your immediate goal but could affect other aspects.
I strongly advise checking with BMS directly, especially since Terry is a member of this forum. He is the most reliable source for any JB4-related question.

 

[Hacksaw907]

Thank you for your insights.

I would caution against changing the JB4 settings independently. Modifying a single setting might achieve your immediate goal but could affect other aspects.
I strongly advise checking with BMS directly, especially since Terry is a member of this forum. He is the most reliable source for any JB4-related question.

100% agree to consult with Terry first and foremost, especially if you're not experienced with looking at logs to make sure it's doing what you want it to. I've seen my fair share of issues as well where people fiddle with settings that they aren't supposed to, so it's sound advice.

For this particular issue though, my efforts to ask around about it hasn't resulted in a clear solution, so I'm posting what worked for me.

 

[mikegt2]

And Terry responds very fast ! i just sent him some logs couple days ago and within minutes he e-mailed me back and told me how much boost to reduce and at what rpm .

 

[ExtremePowerHouse - MIke]

And Terry responds very fast ! i just sent him some logs couple days ago and within minutes he e-mailed me back and told me how much boost to reduce and at what rpm .

+1 he responds in no time