[rader1]

Here's a bit of information I came across that's a really informative/interesting read.

Credit is due to dzenno

Just wanted to share a VERY interesting find that I came across while learning about the flash fuel control and fuel tables as it relates to the ever so interesting and many times discussed lean AFR at onset of WOT (as you get on it) and post shift. I've harped about this countless times before my ban on e90post indicating this as an issue/limitation with the piggyback fuel control which resulted in an eventual ban.

This has always baffled me and always weirded me out on both the popular piggyback tunes (procede and the jb). I've talked many times about it with Shiv back in the day, not sure if I mentioned it to Terry, but basically my questions arose post-install of RBs while trying to dial in low RPM high load AFRs. No matter what you'd do on the procede OR on the JB the initial low RPM AFR with the RBs would almost always be higher than 13.5, 14 or even leaner. This is also the case on stock turbos (not as noticeable) and also noticeable on Shiv's latest Procede AFR logs (see FBIS' procede logs).

Basically the reason the N54 is so hard to richen up below a certain RPM down low is due to a special fuel mode it runs there. It is called lean spool mode, very common thing on many platforms. Therefore, going WOT while actual boost is significantly lower than target will make the DME switch from normal fuel mode to lean spool fuel mode. DME purposely, because of its stock programming, will make AFR run in accordance to a special fuel table while turbos are spooling to speed the spool up, up to a certain RPM where lean spool mode won't be allowed.

If any of you have ever wondered why we see lean spikes at the onset of WOT with the piggies, or post shift for that matter, its the DME intervening and going into LEAN SPOOL fuel mode prior to the boost reaching target

Is this lean spool mode a problem with the piggies? I think DI is the saviour there and its obviously working out fine. Is it better to have direct control over it? Definitely a cleaner approach BUT if you can get around it with a piggy then as far as the motor is concerned it doesn't care how you provide it with the fuel as long as fuel is there. All in all, no drama, just really glad to have come to the root cause of this N54 behaviour.

Cheers

Here's the Former_boosted_is datalog from the 654whp single turbo run. Notice the AFR funkiness at WOT onset?




Here's a log from my car with RBs when I ran the procede, older procede version but same issue back then, this time only 13psi:

http://i835.photobucket.com/albums/z...ull1-13psi.png

Another one off my car back in the day:
http://i835.photobucket.com/albums/z...ull5-13psi.png

Here's what a pigyback tuner had to add.

Most tuning systems have "tip in" fuel enrichment and I'm sure the MSD8X is no exception. But the issue with post shift and spool up fuel trims (if you consider it an issue) is a little more fundamental. The starting point for fueling is the open loop tables. Those are extended up to 34% via learned fuel trims. Then the piggyback further extends it with a fuel pressure bias. But the starting point is the open loop tables. During spool up and post manual shift load reported back to the DME is very low. So the open loop tables call a relatively small amount of fuel. Low starting point means even with the additive for fuel trims and bias we just can't get as much fuel as we might like in those instances. When the DME thinks its making 1psi and its actually making 7psi there is only so much you can do.

But generally speaking I don't see fueling as much of an issue for 480-500rw with meth, even with the leaner tip in. Beyond that I think having a flash loading that corrects the open loop tables the right way is the way to go.

[Jake@MOTIV]

The greatest part about the lean spool table is that certain tuning companies allow you to set the max rpm that table can be active if conditions are met or simply change the table to reflect the targets you would like for actual values being reported instead of fake ones.

[onesuperboi]

Thanks for the info. It's always refreshing to have some technical information discussed in this section of the forum.

However, I have a feeling this thread will be closed soon so read it while you can.

[BES335xi]

Thanks for the info, too bad alot of the tech guru guys were banned from here and its become alot more like which intake/fmic should i buy..

[OpenFlash]

AFAIK, there is no "lean spool" feature active in the MSD80/81. At least not in the traditional sense. I believe what most people are seeing is the partial load/low RPM AFR targets (which are considerably leaner than high load/high RPM AFR target) and the time it takes for the closed loop fuel control system to reach them during a dynamic load swing.

FWIW, here is the AFR table in a stock DME:

[klipseracer]

Originally Posted by BES335xi

Thanks for the info, too bad alot of the tech guru guys were banned from here and its become alot more like which intake/fmic should i buy..

Definitely getting banned for that comment.

[rader1]

Originally Posted by shiv@vishnu

AFAIK, there is no "lean spool" feature active in the MSD80/81. At least not in the traditional sense. I believe what most people are seeing is the partial load/low RPM AFR targets (which are considerably leaner than high load/high RPM AFR target) and the time it takes for the closed loop fuel control system to reach them during a dynamic load swing.

FWIW, here is the AFR table in a stock DME:

If that's the case then why would there be a user adjustable lean spool table?

It doesn't make a lot of since to me that it would go into a low load fuel table when it sees a high requested load and actual load ramping up.

[OpenFlash]

Originally Posted by rader1

If that's the case then why would there be a user adjustable lean spool table?

It doesn't make a lot of since to me that it would go into a low load fuel table when it sees a high requested load and actual load ramping up.

Not sure what user adjustable table you are referring to. Nor do I fully understand your second statement.

[Lulz_M3]

Subscribed, and extremely interested. I haven't logged fuel modes on Cobb but I know it is one of the parameters.

[Ilma]

This is extremely interesting stuff.

I have noticed for quite some time that my timing will flatline post shift more readily the higher my open loop value is set to.

I seem to be able to manipulate the timing drop by using a smaller value for the open loop user adjustable.

This in turn makes my fuel trims rise higher......but this configuration seems to work better for me most of the time.

Does anyone know if the open loop setting adjusts the fuel pressure or injector pulse cycles?

[Lulz_M3]

Originally Posted by shiv@vishnu

Not sure what user adjustable table you are referring to. Nor do I fully understand your second statement.

Cobb has referenced in their materials that the DME has various fuel modes, one being "spool mode."

[Jake@MOTIV]

Shiv - just because you don't have everything unlocked or found doesnt mean it doesnt exist. This is why you have that spike. Here is a screen shot I took of that option for you. Sorry for blocking out all the other tables but its not my place to show more things you may have not been made aware of yet.



Disclaimer - I am not hating. Your single kit is great and you do tons for this community. The flash software you have is just a bit outdated as it was on display here years ago. Cobb has completely decompiled the DME - I know I'd love to see what you could do with a flash tune that was fully capable. You show that one table but I have more fuel tables than the fingers on my hand when making custom maps for my AP.

[Joshboody]

There's no leaner afr during spool... Dme just has leanish afr in low and mid range. You can confirm this by logging cobb map0 requested afr, fuel pressure and idc. It will be a smooth transition with potentially an addition fuel add table during spool. I could be wrong, but doubt it.

Ilma, piggies bias fuel pressure only. At first i thought this was only increased fuel pressure, but depending on your fuel correction, dme may not be able to reach target pressure so it compensates with ipw.

This is a good subject.

[Jake@MOTIV]

Originally Posted by Joshboody

There's no leaner afr during spool... Dme just has leanish afr in low and mid range. You can confirm this by logging cobb map0 requested afr, fuel pressure and idc. It will be a smooth transition with potentially an addition fuel add table during spool. I could be wrong, but doubt it.

Ilma, piggies bias fuel pressure only. At first i thought this was only increased fuel pressure, but depending on your fuel correction, dme may not be able to reach target pressure so it compensates with ipw.

This is a good subject.

Incorrect. If you would like I will discuss it with you privately off e90 in casual conversation. I posted a screen shot I took above but thats the extent I will go into it on here.

[Joshboody]

Cant see the table FL, rich or leaner targets?

[Jake@MOTIV]

I removed all values. I simply left the title of the table showing its there. You can also adjust the max RPM that spool mode is able to be used. So if you wanted it gone you could lower the RPM or simply copy your primary bank 1 / 2 fuel tables into the spool mode and youd could avoid it all together.

I really don't want to go into detail much on this publically. Arguing with Shiv is a bit tedious because he has a vast knowledge of a lot and is a salesman at the same time. I respect him twice over but its just something not worth my time because publically he will hold a position and the people who follow him will believe it. I am not saying he lies to people at all. Just internet arguements on here will not be something I feel like engaging in. I have fact and evidence as I have software in front of me with maps and tables.

I really don't want to go into more detail on here. I just came in to provide a screen shot showing the table that does exactly what me and dzenan were talking about. Shiv may not have access to these parts of the dme with his flash software as its older and cobb has spent far more time than the creators of what he is using did, but it is there, and is the reason he has those lean spikes. It's programmed right in the factory table for that condition specifically - lean spool.

[OpenFlash]

Originally Posted by FlyLow335i

Shiv - just because you don't have everything unlocked or found doesnt mean it doesnt exist. This is why you have that spike. Here is a screen shot I took of that option for you. Sorry for blocking out all the other tables but its not my place to show more things you may have not been made aware of yet.



Disclaimer - I am not hating. Your single kit is great and you do tons for this community. The flash software you have is just a bit outdated as it was on display here years ago. Cobb has completely decompiled the DME - I know I'd love to see what you could do with a flash tune that was fully capable. You show that one table but I have more fuel tables than the fingers on my hand when making custom maps for my AP.

I think you are many too many assumptions about what tables we have defined and what we call them. Judging by the size of the table you posted, we have that as well. But we don't refer to it as a Fuel Spool map because that is not exactly how it works. Then again, this is just based on my testing.

Also, the "age" of my tuning interface is a irrelevant. It is an open source ROM editor which requires a user defined XML file (one for each dme software version). It's a tool, not a fashion accessory. It's really not worth starting a debate on how the dme works on the Internet. I'd rather show what we can do with it on the dyno, street and track.

[Joshboody]

I have logged many parameters on map0 and didnt see evidence of leaner targets during spool... Although i wasn't looking for this specifically. This is not the reason piggies show a leanish spike in the logs though as the OP stated.

[Jake@MOTIV]

The size of the table is irrelevant. They are all adjustable. That is just what the axis were set to. All of the tables can change resolution based on what the person who has the coding abilities wants it to look like. I can change the scaling and load values to represent different ranges etc. I am not trying to teach you anything or prove you wrong in anyway. Simply discussion. I know you are used to fighting with people on here and always having to go on the offensive or defensive but assure you I have no issue or case to prove. I was just providing information. Its obvious you know these things. Your table screen shot'ed above has the same axis as the one i screen shot'ed. Thats because its just the unscaled / unchanged table decompiled from the dme. That can change based on what is needed for what table for any one of thousands of reasons.

Anyways - I am passing out. I just wanted to reiterate im not trying to argue with you. I was just posting up something because earlier you said:

AFAIK, there is no "lean spool" feature active in the MSD80/81. At least not in the traditional sense. I believe what most people are seeing is the partial load/low RPM AFR targets (which are considerably leaner than high load/high RPM AFR target) and the time it takes for the closed loop fuel control system to reach them during a dynamic load swing.

FWIW, here is the AFR table in a stock DME:

Anyways - I am looking forward to customer reviews of your single kit. It is a work of art and will be a lot of fun come fall when customers starting hitting the track with favorable DA's. I can't wait to see what poeple run. Congrats!!

[Dave W.]

It's good to see that BMW is still using code features that are similar to the older Bosch code. The fuel tables posted above have a similar layout to the tables in my 1987 Porsche! Now I'm really curious to see a stock ROM!

BTW the table is labeled 'FUEL (SPOOL)'. It doesn't say it's 'lean spool' unless all of the values are lean? I'm not asking to see the table, I'll take your word for it if it's leaner than the stock fuel maps.

[Ilma]

Originally Posted by Joshboody

Ilma, piggies bias fuel pressure only. At first i thought this was only increased fuel pressure, but depending on your fuel correction, dme may not be able to reach target pressure so it compensates with ipw.

This is a good subject.

Seems that way

I can strongly correlate that I get better post-shift timing recovery when fuel trim values are high, so maybe that causes the DME to use more IPW.

If having a high OL value = higher fuel pressure, then my engine doesn't seem to like this as much as lower pressure and more IPW.

[OpenFlash]

Originally Posted by FlyLow335i

Shiv - just because you don't have everything unlocked or found doesnt mean it doesnt exist. This is why you have that spike. Here is a screen shot I took of that option for you. Sorry for blocking out all the other tables but its not my place to show more things you may have not been made aware of yet.



Disclaimer - I am not hating. Your single kit is great and you do tons for this community. The flash software you have is just a bit outdated as it was on display here years ago. Cobb has completely decompiled the DME - I know I'd love to see what you could do with a flash tune that was fully capable. You show that one table but I have more fuel tables than the fingers on my hand when making custom maps for my AP.

I think you are making some unfair assumptions. My only point that I have been trying to make from the start is that it is not a conventional "lean spool" table as it has been described (and apparently named in your Cobb software). But the name of the table is irrelevant if you know how it works. Here's the table I believe you are referring to in my rom editing software. The values in the table will be different from what you have in yours I'm guessing: