N54 Exhaust Burble XDF Tables

carabuser

Sergeant
Oct 2, 2019
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Z4 35i & 335i
I posted this on the "other" forum but seems there's a lot of discussion about custom tuning here so thought I'd repost here too.

I've defined some extra tables that would be useful for people that want exhaust burbles that don't use MHD, or people like me that use MHD but like having full control over their custom tune or want the ability to "send it" with the exhaust burbles.

I'll upload the XDF definitions for:
I8A0S
IJE0S
INA0S

The INA0S XDF is a cleaned up version of my personal XDF. It's just the public one that also has the full throttle correction definitions added and a few other small changes.I'm open to any feedback or bug fixes, defining tables between multiple ROMS leaves plenty of room for copy paste errors. I've tested the XDF tables for INA0S since that's what my car run on. Someone with I8A0S tested the burble tables and said everything worked well.


Here's some values for a guide. These are the only three that really need changing. The duration tables define how long between taking your foot off the accelerator and fuel injection being cut. As you can see the stock values are very short for most cars, but for the Z4 they were increased to give us a more sport exhaust sound.

The timing table is not something I fully understand, I read the MSD81 technical specification which has a section on "minimum ignition angle" and found that this is the table responsible for the ignition timing during overrun but it's not as simple as just targeting the angle entered in the table, it is influenced by other factor and differential tables. The axis in this table is mg/stk, our engine sits firmly in the 75mg/stk area during overrun so just work on that area.

Stock values for INA0S car (335i)
Stock 335i.png

Stock values for INA0S car (Z4)
Stock Z4.png

My current values as a starting point, somewhat comparable for the MHD "medium" setting.
Modified.png
 

Attachments

  • Fuel Cut XDF.zip
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chrisdfv

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Aug 29, 2017
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I messed around a little with these today, but it definitely seems like we are missing tables for the timing target.
 

Asbjorn

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Mar 10, 2018
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This is super informative and explains alot.

So just to clarify, the values for normal apply to the dsc=off mode as well right? I always use dsc=off on track, and would really love the exhaust burbles to be 100% gone in that environment. On the other hand it would be nice to have the sport burbles in normal mode, as I never use sport mode.

BTW has the steering response tables been defined for Z4 35i and 35is? They say 35is is different from 35i. I can also feel that dsc=off steering is similar to sport.
 
Last edited:

carabuser

Sergeant
Oct 2, 2019
422
270
0
UK
Ride
Z4 35i & 335i
I messed around a little with these today, but it definitely seems like we are missing tables for the timing target.

I don't think there is a timing target for this engine mode. There is a lengthy calculation that uses that defined table as an offset during trailing throttle (PU) engine operation. If decreasing that offset table doesn't change your timing target in trailing throttle then there are some toggles that may enable it that I came across. They looked to be enabled on all ROMs by default though.

This is super informative and explains alot.

So just to clarify, the values for normal apply to the dsc=off mode as well right? I always use dsc=off on track, and would really love the exhaust burbles to be 100% gone in that environment. On the other hand it would be nice to have the sport burbles in normal mode, as I never use sport mode.

BTW has the steering response tables been defined for Z4 35i and 35is? They say 35is is different from 35i. I can feel that dsc=off steering is similar to sport+, whereas sport is similar to traction and normal is different from all of those, and only really great for parking and cruising.

These values will apply whenever the car goes into PU or PUC engine mode. The only thing that takes precedent over those modes during no throttle input are stability control activation, misfires and a DCT gear shift. All of which have their own torque reduction and fuel cut timers. If you're in sport or sport+ mode then it'll use the sport table for duration, if you are in normal mode but with DSC off then it should use the normal table.

I'm not aware of a difference with the steering response between 35i and 35is but if there is any it'll be in the module that handles the steering. The DME has toggles for cariations like electronic steering which I think are just used for torque loss and idle management tables as a way of modelling increased engine load from the steering system.

I made a clumsy attempt at defining all the differences between a 35i and 35is ROM, see the screenshot below. The 35i bin that I used had a manual transmission so a few of the tables are related to that.
Untitled.png
 
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chrisdfv

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Aug 29, 2017
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I don't think there is a timing target for this engine mode. There is a lengthy calculation that uses that defined table as an offset during trailing throttle (PU) engine operation. If decreasing that offset table doesn't change your timing target in trailing throttle then there are some toggles that may enable it that I came across. They looked to be enabled on all ROMs by default though.

Interesting. I took a few logs of no burble, mhd burble and it's various settings.
Then I tried my own table values, but find that even with very negative table values, I don't have same amount offset in timing during decel, nor does it stay at the value like MHD's settings.
 

carabuser

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Oct 2, 2019
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Z4 35i & 335i
Interesting. I took a few logs of no burble, mhd burble and it's various settings.
Then I tried my own table values, but find that even with very negative table values, I don't have same amount offset in timing during decel, nor does it stay at the value like MHD's settings.
What does your timing table look like and what do the logs show?
 

carabuser

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Oct 2, 2019
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Z4 35i & 335i
Yes. burble toggle in MHD is disabled at flash time.

I contacted the chap who tested the tables on his I8A0S car and he said he used tweaks to the main table.

MHD only manipulates the Timing (Main) table with the burble slider since Jake mentioned that they didn't know about the other table.

I had a look for the toggle that enables/disables the use of the timing offset during trailing throttle and it appears in the MSD81 IKC0S Damos but not in the MSD80 I460S Damos so it's possible that the logic that deals with differential timing during trailing throttle was added in MSD81.

If I drop the timing in the minimum ignition angle table by 1 degree I see exactly the same behaviour in my logs. I'd be interested to see if someone with IJE0S also sees the same behaviour.
 

chrisdfv

Corporal
Aug 29, 2017
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I contacted the chap who tested the tables on his I8A0S car and he said he used tweaks to the main table.

MHD only manipulates the Timing (Main) table with the burble slider since Jake mentioned that they didn't know about the other table.

I took logs with the burble slider set to "stock" and the timing values during decel corresponded with the trailing throttle timing table, not my main timing table.
 

AzNdevil

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Nov 4, 2016
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This is super informative and explains alot.

So just to clarify, the values for normal apply to the dsc=off mode as well right? I always use dsc=off on track, and would really love the exhaust burbles to be 100% gone in that environment. On the other hand it would be nice to have the sport burbles in normal mode, as I never use sport mode.

BTW has the steering response tables been defined for Z4 35i and 35is? They say 35is is different from 35i. I can feel that dsc=off steering is similar to sport+, whereas sport is similar to traction and normal is different from all of those, and only really great for parking and cruising.

steering response table is in ncsexpert instead of dme map IIRC

I contacted the chap who tested the tables on his I8A0S car and he said he used tweaks to the main table.

MHD only manipulates the Timing (Main) table with the burble slider since Jake mentioned that they didn't know about the other table.

I had a look for the toggle that enables/disables the use of the timing offset during trailing throttle and it appears in the MSD81 IKC0S Damos but not in the MSD80 I460S Damos so it's possible that the logic that deals with differential timing during trailing throttle was added in MSD81.

If I drop the timing in the minimum ignition angle table by 1 degree I see exactly the same behaviour in my logs. I'd be interested to see if someone with IJE0S also sees the same behaviour.

i think other tables might need to be changed to make use of the PU maps for burble especially "Exhaust gas temperature protection - Minimun ignition angle limitation"
 
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carabuser

Sergeant
Oct 2, 2019
422
270
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UK
Ride
Z4 35i & 335i
I took logs with the burble slider set to "stock" and the timing values during decel corresponded with the trailing throttle timing table, not my main timing table.

So you can manipulate the trailing throttle timing using the new table? or am I reading that wrong?

i think other tables might need to be changed to make use of the PU maps for burble especially "Exhaust gas temperature protection - Minimun ignition angle limitation"

You're correct in that there are other tables that reference calculated exhaust temp to limit the timing but those shouldn't interfere in these circumstances. I did declare the other two correction tables on the ignition map for PU mode but they both reference coolant temp and once it gets above 180 they have no influence on the values.
 

KClemente

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Nov 26, 2019
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For me, i've had the best luck by manipulating both Main at trailing throttle ignition angles. Trailing throttle will only work when moving, and the main ignition angle is a supplementary map for inducing burble or pops on a standing rev and keeping the timing retarded on quick shifts.

Its safe to say that there are more than 100 maps controlling any part of the ignition, and I don't think many of them are even used. There are factors, deltas, bases, and optimal maps.
 
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KClemente

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Nov 26, 2019
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I took logs with the burble slider set to "stock" and the timing values during decel corresponded with the trailing throttle timing table, not my main timing table.

Did you not uncheck the burble setting? If it's set to "stock" and not unchecked, MHD will still overwrite whatever you have set on the main timing table (I'm pretty sure)

Looking through the maps, at 950 degrees celsius (EGT), the minimum ignition angle is only -15 degrees. At 1000 degrees celsius, the minimum ignition becomes 0 degrees. Everything else below 950 degrees linearly goes down to -80. Though I don't know anyone crazy enough to retard timing all the way to -80 degrees, it's possible.

Without an egt gauge or knowing how the DME calculates EGT its hard to know if we're hitting the limitation.
 
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chrisdfv

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Aug 29, 2017
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So you can manipulate the trailing throttle timing using the new table? or am I reading that wrong?

When the slider is set to " stock" timing values reflect those in the trailing throttle table no the values in my main timing table. How ever if I retard the timing angle in the trailing throttle table, the timing value during decel doesn't match up. It's negative, but no where near the values input in the table and it's not a constant value.
 

iminhell1

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Jun 17, 2018
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So I don't care about burbles,
What I'm curious about is if these tables can affect the down rev? When you free rev the car it takes too long to come back to idle. I'd like that to be faster.
 

KClemente

Corporal
Nov 26, 2019
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E90 335i
So I don't care about burbles,
What I'm curious about is if these tables can affect the down rev? When you free rev the car it takes too long to come back to idle. I'd like that to be faster.
From my understanding, you would maybe have to advance timing a little bit in the main ignition map because shifts don't trigger trailing throttle mode (PU). Also you would have to define some icv airflow tables and cut some air out between shifts.

Also the mechanical stuff like lightweight flywheels and such.