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Discussion Starter · #1 · (Edited)
I have been doing a lot of datalogging on my truck just driving around town trying to dial in my timing for 94 octane. I noticed that my spark source is often "Base/MBT" but I also am getting active KR at the same time. I was under the impression that MBT was the maximum timing you would want to be at since its where maximum torque is produced? So why does the KR stay active while the sparksource is MBT?

Here is an example:

173304


You can see KR stays active for a while on the graph at the bottom right and throughout that entire time the Spark Source is Base/MBT but with +5 to +3 KR
 

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Why dont you check individual? It looks like you're just crusing there, so who cares. I reference the base/mbt while cruising or light driving too in my log file.

How did you get those brake tq pids? They are highighted in mine and wont let me add them.
 

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Discussion Starter · #3 ·
Why dont you check individual? It looks like you're just crusing there, so who cares. I reference the base/mbt while cruising or light driving too in my log file.

How did you get those brake tq pids? They are highighted in mine and wont let me add them.
Individual knock does not work on my truck for Cylinder 1. 2-6 work fine. So I have gone back to Global.

Just trying to understand how the PCM actually uses the MBT tables. I am not worried about it, but I am curious if the PCM uses the MBT tables as a "limiter" or does it actually switch over to the MBT table in some instances as the base spark source instead of the Boarderline tables.

In my head I always assumed that the PCM used the Boarderline table all the time, and if the Boarderline + any advancement from the OAR or KR exceeded the timing in the MBT table, it would just cap the timing. But I get the feeling that it has some kind of threashold where if it exceeds a certain timing it actually jumps to the MBT table as the base for the timing and then KR is still implemented but only positive.

They were just available in the list of PID's. I didnt have to do anything I don't think.
 

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Discussion Starter · #5 ·
And i should mention that, after looking through a bunch of my logs, the KR is only ever positive while the spark source is MBT. it never goes negative, which makes sense being that there is no point in exceeding MBT.
 

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Discussion Starter · #6 ·
BTW, I wonder if this has to do with why some of us get crappy OAR's when we are just cruising around town. The spark source jumps to MBT and then KR starts going positive since the MBT table might be more advanced than the boarderline table, and it kills the OAR.
 

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I have been doing a lot of datalogging on my truck just driving around town trying to dial in my timing for 94 octane. I noticed that my spark source is often "Base/MBT" but I also am getting active KR at the same time. I was under the impression that MBT was the maximum timing you would want to be at since its where maximum torque is produced? So why does the KR stay active while the sparksource is MBT?

Here is an example:

You can see KR stays active for a while on the graph at the bottom right and throughout that entire time the Spark Source is Base/MBT but with +5 to +3 KR
Base/MBT simply means the source of your spark advance at that moment is from the MBT Tables. For example, lets just pretend we only have 2 tables, Base/MBT or Borderline. The PCM will use the spark from whichever table has the LOWER spark amount, and the source will show which of those two in our example is being used.

EcoBoost have Mapped Points or Weighing Factors depending on the software. If you log the these Mapped Points, and let's say it says 80% on Mapped Point 14. That means 80% of the spark delivered is coming from either Base/MBT Mapped Point 14, or its coming from the Borderline Mapped Point 14.

For EcoBoost, in Wide Open Throttle areas, you will usually find in factory form, the MBT tables are way higher than the borderline, hence you will see Borderline as the spark source mostly because it's lower.

EcoBoost also have about 2 or 3 other limiting tables, such as Max Spark to Limit Combustion Pressure, Maximum Spark for IPC, and there's another one that eludes me at the moment. These can show up, usually at WOT. For example, I use the Spark Cylinder Pressure Limit table as a ceiling for my tunes, which will cause a different spark source when hit.

Also, as far as I understand MBT, it's a little different than that. MBT is a theoretical limit of the engine in regards to spark advance, at STOICH, with no boost but at 100% VE. So this would be done in a lab or through modeling I'm assuming. Once we add actual boost, heat and all the other things, MBT for a factory boosted engine usually resembles something that we would NEVER run because it's just not reasonable for the cylinder pressure a boost engine will make. If you look at a Coyote, you will see that MBT is actually very close the Borderline and you sometimes have to move MBT up out of the way.

For your tune file, it seems like where you are at in that spot and mapped point, you have enough spark added to Borderline and maybe some other adders, that it hits MBT.

One last thing to possibly confuse you. It seems like in HP tuners, they have two knock retard pids. I'm not sure which one is which, but they read OPPOSITE. Yeah I know, dumb. I dont think they did that by design, its probably Ford. The easy way to figure out which way your pid reads, is go to the Knock Advance table and 0 it out for a test. Now your knock sensor cannot add timing, so if you see any movement, you know it is pulling timing. Then you can set your advance table back and you know which way it goes for adding and retarding timing.

Hope this helps.

-BoostKing
 

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Base/MBT simply means the source of your spark advance at that moment is from the MBT Tables. For example, lets just pretend we only have 2 tables, Base/MBT or Borderline. The PCM will use the spark from whichever table has the LOWER spark amount, and the source will show which of those two in our example is being used.

EcoBoost have Mapped Points or Weighing Factors depending on the software. If you log the these Mapped Points, and let's say it says 80% on Mapped Point 14. That means 80% of the spark delivered is coming from either Base/MBT Mapped Point 14, or its coming from the Borderline Mapped Point 14.

For EcoBoost, in Wide Open Throttle areas, you will usually find in factory form, the MBT tables are way higher than the borderline, hence you will see Borderline as the spark source mostly because it's lower.

EcoBoost also have about 2 or 3 other limiting tables, such as Max Spark to Limit Combustion Pressure, Maximum Spark for IPC, and there's another one that eludes me at the moment. These can show up, usually at WOT. For example, I use the Spark Cylinder Pressure Limit table as a ceiling for my tunes, which will cause a different spark source when hit.

Also, as far as I understand MBT, it's a little different than that. MBT is a theoretical limit of the engine in regards to spark advance, at STOICH, with no boost but at 100% VE. So this would be done in a lab or through modeling I'm assuming. Once we add actual boost, heat and all the other things, MBT for a factory boosted engine usually resembles something that we would NEVER run because it's just not reasonable for the cylinder pressure a boost engine will make. If you look at a Coyote, you will see that MBT is actually very close the Borderline and you sometimes have to move MBT up out of the way.

For your tune file, it seems like where you are at in that spot and mapped point, you have enough spark added to Borderline and maybe some other adders, that it hits MBT.

One last thing to possibly confuse you. It seems like in HP tuners, they have two knock retard pids. I'm not sure which one is which, but they read OPPOSITE. Yeah I know, dumb. I dont think they did that by design, its probably Ford. The easy way to figure out which way your pid reads, is go to the Knock Advance table and 0 it out for a test. Now your knock sensor cannot add timing, so if you see any movement, you know it is pulling timing. Then you can set your advance table back and you know which way it goes for adding and retarding timing.

Hope this helps.

-BoostKing


I’m going to have to re-read that a couple times…


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2021 Powerboost Platinum FX4 Kodiak Brown
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I’m going to have to re-read that a couple times…


Sent from my iPhone using Tapatalk
Not me!

There are things that I NEED to know because I will be..... unfulfilled(?) until I have my head around it. Until I am qualified to manage decisions regarding.

Then there are things that I see like this ^^^^ and I tell myself THAT is something THAT man was put here to master. And then I simply put my faith in his good hands.

Remarkably generous to share with me (us) the information, but I don't think I will ever ask for more. That's enough for me to know what I don't NEED to know. :)

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Discussion Starter · #10 · (Edited)
Base/MBT simply means the source of your spark advance at that moment is from the MBT Tables. For example, lets just pretend we only have 2 tables, Base/MBT or Borderline. The PCM will use the spark from whichever table has the LOWER spark amount, and the source will show which of those two in our example is being used.

EcoBoost have Mapped Points or Weighing Factors depending on the software. If you log the these Mapped Points, and let's say it says 80% on Mapped Point 14. That means 80% of the spark delivered is coming from either Base/MBT Mapped Point 14, or its coming from the Borderline Mapped Point 14.

For EcoBoost, in Wide Open Throttle areas, you will usually find in factory form, the MBT tables are way higher than the borderline, hence you will see Borderline as the spark source mostly because it's lower.

EcoBoost also have about 2 or 3 other limiting tables, such as Max Spark to Limit Combustion Pressure, Maximum Spark for IPC, and there's another one that eludes me at the moment. These can show up, usually at WOT. For example, I use the Spark Cylinder Pressure Limit table as a ceiling for my tunes, which will cause a different spark source when hit.

Also, as far as I understand MBT, it's a little different than that. MBT is a theoretical limit of the engine in regards to spark advance, at STOICH, with no boost but at 100% VE. So this would be done in a lab or through modeling I'm assuming. Once we add actual boost, heat and all the other things, MBT for a factory boosted engine usually resembles something that we would NEVER run because it's just not reasonable for the cylinder pressure a boost engine will make. If you look at a Coyote, you will see that MBT is actually very close the Borderline and you sometimes have to move MBT up out of the way.

For your tune file, it seems like where you are at in that spot and mapped point, you have enough spark added to Borderline and maybe some other adders, that it hits MBT.

One last thing to possibly confuse you. It seems like in HP tuners, they have two knock retard pids. I'm not sure which one is which, but they read OPPOSITE. Yeah I know, dumb. I dont think they did that by design, its probably Ford. The easy way to figure out which way your pid reads, is go to the Knock Advance table and 0 it out for a test. Now your knock sensor cannot add timing, so if you see any movement, you know it is pulling timing. Then you can set your advance table back and you know which way it goes for adding and retarding timing.

Hope this helps.

-BoostKing
Is this why some of us get crappy KR and OAR under light load? Is it because it jumps to using the MBT tables and the KR goes positive since they are more aggresive than the Boarderline?

Also, the MBT tables have loads up to 1.8 i think on my 2014 tune. wouldnt that mean they assumed there was boost when they built them?
 

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Is this why some of us get crappy KR and OAR under light load? Is it because it jumps to using the MBT tables and the KR goes positive since they are more aggresive than the Boarderline?

Also, the MBT tables have loads up to 1.8 i think on my 2014 tune. wouldnt that mean they assumed there was boost when they built them?
Great questions, and keep in mind, I can only speculate with some of this. Ford will never share this information so we as calibrators do our best to make sense of what a bunch of engineers decided was best.

For your first part about jumping to MBT, well it can't, UNLESS the MBT table is LOWER than the Borderline. (not yelling). The PCM always uses the lowest value between the two, so it wont jump UP, it will only stay to which ever is lower.

That said, you are right, the MBT tables do have load values above 1.0, hence they are intended for boost, but I would tend to believe this was modeled some how. I mean running stoichiometric combustion at 1.8 load with 19* of spark advance seems a bit dangerous on a higher compression turbocharged motor. Though I really dont know how they achieve the values they do.
173394


Truth is we may never know exactly why the MBT tables are the way they are, or how they are. I just know that in the logic, the PCM will always choose the lower of the two. It's common practice in even GM and Dodge stuff as well.

I dont believe your knock issue is because it is jumping from Borderline to MBT. Think of it like this if you may, your Borderline table let's assume is at 7*, and assume for that same load and RPM and such, your MBT is now at 6.5*. The PCM is going to switch to the MBT, which in this case and as always this is the lower of the two spark values....

I think in my experience, most of the time people have crappy OAR and have KR under light load is two things, poor quality fuel, or too much boost down low with too much spark. Most want the boost because it really makes that low end torque feel good. It can be as much as an extra 2-3 psi down low with the same timing from the factory. I like to combat this with using the tip in retard table to take more spark out during tip in and slowing the addition of spark. It's a balance act for sure.
 
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