Help with MHD 3D boost ceiling

ddoublee

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Jul 31, 2019
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First off, I'd like to say hello, I've been lurking here for a long time, but haven't really posted yet.

Car setup - 2007 335i, manual trans, MMP1k turbos, FBO, PR stage 2.5 bucket lpfp, DI only

For the last couple of years I have been running a custom flex fuel tune from a known tuner in the community, but I won't mention any names. This tune was not very good, lots of overboosting, throttle closures, and maxxed out trims. I have experience tuning other platforms in the past, mainly Hondata, but I had a lot to learn about N54 tuning before I felt comfortable doing it myself.

I have recently begun working on fixing my tune myself, and I'm trying to learn all that I can. I began by taking my existing tune and converting it to the new MHD+ map switch base. I first worked on getting my fuel trims in line on both pump gas and e35 blend.

Once getting my trims looking better, I began working on boost control, and I was excited to try the MHD 3D boost ceiling. I turned on the feature and began working through my issues with throttle closures and overboost. I found my WGDC base table was never scaled properly, and after fixing the scaling, and working on the base tables a bit, my boost control seems to be working well. However, I am now noticing my boost target is inconsistent despite using the 3D ceiling.

My tune is flex fuel, set for full interpolation at E50, and I am currently running E35. My pump 3D ceiling is set to 18 psi and 180 load target, and flex 3D ceiling is set to 26 psi and 187 load target, so I believe both of those load targets should be high enough to not interfere. Most of the time, what I am seeing is the boost target will shoot up to about what I expect around 24.5 psi around 4000 rpm, but will slowly taper all the way to redline, being around 22.5 at 5000 rpm, and 20.5 by 6000 rpm.


Here is a log showing the taper.

Log with flat target until 5500 RPM
This log in this link was from just a few minutes prior, the same map revision, but in this one, boost target is flat as I would expect from 4000 to 5500, and then suddenly boost target drops by 2 psi and there is a small throttle closure.

I have some other logs that I won't include here because they are not very good due to wheel spin, but those logs show targets as low as 20 psi.

I'm just trying to understand, is this taper to be expected considering my load and ceilings are set flat? What can I do to adjust this behavior? Hopefully this post makes sense, as I have a tendency to ramble, but if I can provide an clarification or more detail, please let me know. I'd be happy to post my bin file if anyone cares to look over it.
 

JohnDaviz

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Jan 6, 2019
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First Post here shows some relevant tables:

How do your tables look like?
 

ddoublee

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Jul 31, 2019
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First Post here shows some relevant tables:

How do your tables look like?
1701019255941.png
 

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JohnDaviz

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Jan 6, 2019
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I have set all cells in both tables to 1.012. Try that.

Also you are hitting the Load Target from 4900 rpm to the end nearly. Increase the Load Target limit also to clear that as a restriction also.
 

ddoublee

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Jul 31, 2019
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First Post here shows some relevant tables:

How do your tables look like?
After doing some reading on the thread you linked, it very much seems like this is where I need to be looking.

And yes, I can't believe I didn't see that I was hitting load requested ceiling, thank you for mentioning this. I was thinking load ceiling should have been 187 but I forgot I'm not fully interpolating into the FF table.

What about BRO, BLM and Boost ceiling? Should I adjust those?
1701022999880.png
 

JohnDaviz

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I have BRO at 84 on all cells. But i have this since i started in 2018 so i have absolutely no knowledge about this table as it never was a topic for me.

BLM and Boost ceiling look fine.

About Boost ceiling.. My Boost Target is always 0.5psi lower than what i put into the cells. Maybe this comes from the BRO tables.. But i don´t care.
 

ddoublee

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Jul 31, 2019
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Thanks for the info, I'm first gonna raise the load target a bit higher, and then I'll work on the BPTM tables.
 

KClemente

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Nov 26, 2019
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Both boost pressure target modifiers need to be set to 1.0 across the board.

keep your boost request offset stock too. It's been a while since development, but I don't think we had them set to 1.0 during flash, but they will definitely influence targeting
 

JohnDaviz

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Both boost pressure target modifiers need to be set to 1.0 across the board.

Don´t set it to 1.0. I thought this is also posted in the other thread. With 1.0 you should always be below your boost target as otherwise you will get throttle closures. But stronger than the "normal" throttle closures one may experience.
 

KClemente

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Nov 26, 2019
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Since he is using 3D ceiling I think he still needs to set them both to 1.0. Here's a quote from Jake from back when I was testing MHD+ for him.

3D boost target should give proper throttle closure for overboost now. the target will be effected by the pspld eco/dyn tables though so I would set them to 1.0 flat.

Not saying you're wrong though but I've had mine set that way for years now and get consistent boost targeting.
 
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JohnDaviz

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Jan 6, 2019
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Then my apologies :)
I experienced that issue before MHD+ so my information is outdated as it seems! Great!