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Author Topic: Wideband LAMFA  (Read 48561 times)
nokiafix
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« Reply #30 on: June 06, 2012, 05:03:20 AM »

These are retail customer cars so the tuning is aimed more to be safe under all conditions.



I can see what your saying about cylinder filling/load boost v rpm, its like tuning OMEX ecu via MAP and TPS.

But when me7.5 tuned via LAMFA and BTS v rpm, for some reason its works 100% fine at all stages of tune.  The main thing is getting the simulated EGTs corrected and really fully understanding the hardware.


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thom337
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« Reply #31 on: June 06, 2012, 06:02:55 AM »

You basically just said exactly what I have been saying. Except RPM does not factor into the equation.
The correct measurement is combustion chamber temperature and exhaust gas temperature. The higher the combustion chamber temperature gets, the lower the knock threshold. The lower the threshold, the more timing is retarded. The more timing is retarded, the more EGT rises, as more energy is converted into heat. The fact that it occurs with higher RPM is logical, but when you have the ability to fuel off of combustion chamber temperature directly, it is much better than mapping based off of RPM, which is just a side effect of things.
The reason older ECU's are mapped via RPM, is because they don't have an EGT model, they don't have EGT measurements, there is no way to model the combustion chamber.

But the actual req fuel for best power constantly drifts, and if timing is advanced sufficiently, then it is almost directly proportional to EGT.

It's good we have discussions like this though. Perhaps it will remind people, that the ability to change a few numbers in the ECU and the ability to understand the physical processes inside an engine, and understanding *why* every change is made are completely different things.

Combustion chamber temperature and EGT are heavily driven by engine speed. For a given load, as engine speed increases the time between combustion events decreases and so does the time for the cylinder to transfer heat to the head/block/etc. This is kind of the idea i was talking about before where we must not separate our considerations for "engine time" (crank angle) and the "physical time" at which chemical reactions and heat transfer occur. Because of this heavy relationship between RPM and EGT/combustion chamber temp, it makes sense that a model and mapping strategy would be based on both load and RPM where EGT is the driving factor (ie you are using these things: speed, load, thermal mass, lambda, efficiency, etc to predict EGT because it is heavily dependent on them).

You are correct though that if you can map directly off of EGT, that is the way to go as that is what all these load/speed/etc based strategies are trying to predict. It sounded like you were saying there was no physical relationship between the two, but if I understand you correctly now you are actually saying that the influence doesn't matter because you have direct access to the EGT measurement which is the critical measurement here. With that I can certainly agree...and also wish that all 1.8T's came with an EGT sensor.  Embarrassed
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prj
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« Reply #32 on: June 06, 2012, 06:32:14 AM »

You are correct though that if you can map directly off of EGT, that is the way to go as that is what all these load/speed/etc based strategies are trying to predict. It sounded like you were saying there was no physical relationship between the two, but if I understand you correctly now you are actually saying that the influence doesn't matter because you have direct access to the EGT measurement which is the critical measurement here.
Exactly! This is what I have been trying to say from the start Smiley
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With that I can certainly agree...and also wish that all 1.8T's came with an EGT sensor.  Embarrassed
ME7 has a simulated EGT model. This simulated EGT model when calibrated correctly off of a real EGT sensor can be made to work very well without any actual sensor.

There are a million ways to tune things - I just like to model the engine as close as possible.
And the only reason I say that fixing AFR based on LOAD and RPM is incorrect, is because there are better ways available in ME7, and because it is impossible to work out the correct fueling based on LOAD and RPM alone for every situation and every gear.
You can choose a "golden middle" - and that's how almost all the older Motronic cars are mapped as well, but it will never be as good as it could be.
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silentbob
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« Reply #33 on: June 06, 2012, 06:40:00 AM »

Exactly! This is what I have been trying to say from the start :)ME7 has a simulated EGT model. This simulated EGT model when calibrated correctly off of a real EGT sensor can be made to work very well without any actual sensor.

There are a million ways to tune things - I just like to model the engine as close as possible.
And the only reason I say that fixing AFR based on LOAD and RPM is incorrect, is because there are better ways available in ME7, and because it is impossible to work out the correct fueling based on LOAD and RPM alone for every situation and every gear.
You can choose a "golden middle" - and that's how almost all the older Motronic cars are mapped as well, but it will never be as good as it could be.

Based on your statements about LAMBTS here I think you didn't fully understand how this is ment to work.

Also there are a lot of situations were you want pre-emptive enrichment to stabilize the combustion just like nyet uses it.
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prj
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« Reply #34 on: June 06, 2012, 06:44:38 AM »

Based on your statements about LAMBTS here I think you didn't fully understand how this is ment to work.
And I think the only point of this statement, as you said it was to cause personal offense.
You might as well say "I think you are an idiot", well, that would be just your opinion Wink

If you think I misunderstand something - then do tell exactly why, and exactly how you picture it. That would be called "constructive criticism". What you are doing now is called "mud slinging".

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Also there are a lot of situations were you want pre-emptive enrichment to stabilize the combustion just like nyet uses it.
I agree, and I do this as well.
FYI I don't fuel solely off of LAMBTS, I use it for additive enrichment when things start to get hot.
« Last Edit: June 06, 2012, 06:48:37 AM by prj » Logged

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silentbob
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« Reply #35 on: June 06, 2012, 08:03:58 AM »

And I think the only point of this statement, as you said it was to cause personal offense.
You might as well say "I think you are an idiot", well, that would be just your opinion Wink

Don't know why you take it this way but I have no such intentions whatsoever.

If you think I misunderstand something - then do tell exactly why, and exactly how you picture it. That would be called "constructive criticism". What you are doing now is called "mud slinging".

Set base EGT enrichment to the same at all RPM's, use FBSTABGM to enrich *based* on the EGT.

So in other words you say that the enrichment to reach a certain EGT is the same on all RPMs. This is obviously not the case like already described a few times here.

KFLBTS (together with dlambts) is the enrichment you need in steady state to limit the EGTs to a certain goal. All the dynamic stuff you described is handled with the enable conditions and the EGT modelling. This is how the function is intended to work when you use it only for component protection.

Bosch component protection is not a controller like other ECU systems that control lambda to reach a certain limit, it's all based on precontrolled lambda 






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prj
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« Reply #36 on: June 06, 2012, 08:34:11 AM »

Don't know why you take it this way but I have no such intentions whatsoever.
Because of the way you stated it, without providing any explanation on where you drew that conclusion. Because you are playing the player instead of playing the ball.
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So in other words you say that the enrichment to reach a certain EGT is the same on all RPMs. This is obviously not the case like already described a few times here.
I never said this. I don't use BTS as main fueling, I don't use EGT as the only fueling either.
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KFLBTS (together with dlambts) is the enrichment you need in steady state to limit the EGTs to a certain goal. All the dynamic stuff you described is handled with the enable conditions and the EGT modelling. This is how the function is intended to work when you use it only for component protection.
A lot easier to achieve nearly the same behavior with FBSTABGM, where you add a certain amount of enrichment based on current calculated EGT.
Of course the theoretical best way would be to have linearized KFLBTS and FBSTABGM together.

Btw, in stock tunes on RS4 FBSTABGM is not used.
Are you going to declare it useless, and "not meant to be used" as well? Wink

My point is to fuel constantly to preemptively decrease EGT. Not tune based on emissions, and then dump fuel when you reach a certain EGT setpoint, and then set lambda rich enough to hold a certain EGT limit.
If you tune for performance, not for emissions, it's just not the way to do things IMO, so obviously you end up using some things "not as intended".
« Last Edit: June 06, 2012, 08:54:45 AM by prj » Logged

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marcellus
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« Reply #37 on: June 06, 2012, 08:44:01 AM »

Not to derail the discussion, but I dont have the FBSTABGM map defined in my m box XDF   Huh  .  Could someone please post the info so I can have the map and follow along with you guys.  Sorry...

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prj
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« Reply #38 on: June 06, 2012, 08:51:51 AM »

Not to derail the discussion, but I dont have the FBSTABGM map defined in my m box XDF   Huh  .  Could someone please post the info so I can have the map and follow along with you guys.  Sorry...

0x150C2, factor 0.000031, 16 bit, LoHi, 4x1
The axis is right before it at 0x150BA, it is EGT, 16 bit, LoHi, 4x1. Factor 0.019531, offset -50

Make sure you look exactly at FR how it is used. It is a multiplier for enrichment. That means for (1-KFLBTS+LAMBTSZW).
« Last Edit: June 06, 2012, 08:55:36 AM by prj » Logged

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nyet
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« Reply #39 on: June 06, 2012, 08:53:57 AM »

Thanks. I'll add it to my next mappack release
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ibizacupra
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« Reply #40 on: June 06, 2012, 09:45:08 AM »

Load is cylinder filling. Not understanding this, is not understanding what Motronic is about.ME7 has an EGT model. If you don't have a properly calibrated EGT model, then you can't use EGT to fuel off. When the EGT model is properly calibrated, it is usually pretty damn accurate.Let's just say, GT30R+, but this is irrelevant, I was saying it tongue in cheek. You'd have to screw up pretty bad to blow up an engine on ME7 anyway. 200hp/litre is baby power for it.

Another question if I may..
EGT model.. and hardware effects on it... eg: higher flowing exhaust manifold, bigger turbos K04 vs GT35, very different scenarios.  do you say the vag egt model is equally valid between very different hardware setups?

I am trying to understand more about the me7 here.. please bare with me. thx
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nokiafix
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« Reply #41 on: June 06, 2012, 10:19:45 AM »

Another question if I may..
EGT model.. and hardware effects on it... eg: higher flowing exhaust manifold, bigger turbos K04 vs GT35, very different scenarios.  do you say the vag egt model is equally valid between very different hardware setups?

I am trying to understand more about the me7 here.. please bare with me. thx

This is where understanding the hardware plays a huge part, If you know the turbo setup is going to be prone to raised EGTs and you want BTS to play a big part to keep the engine safe, then you will need to recalibrate the simulated egt maps buy using and external EGT system and lots of logging and graphing data.   

Or you can just offset TABGBTS to a temp you know and have recorded that works.  This is the way I work, its handy when you have a braked dyno and you can load the turbo upto the max and monitor the elevated egts under the most extream conditions.

With Me7.5 tuning you can try to go too much into detail thinking you have to do it right or a way eveyone says.  IMO just find your own method of tuning me7 which works and is safe.
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silentbob
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« Reply #42 on: June 06, 2012, 10:44:16 AM »

I never said this.

Sure you did. You said
Set base EGT enrichment to the same at all RPM's, use FBSTABGM to enrich *based* on the EGT.
which results in excatly what I have said.

A lot easier to achieve nearly the same behavior with FBSTABGM, where you add a certain amount of enrichment based on current calculated EGT.

What you are trying to create here is a P controler. This will not work properly.

Btw, in stock tunes on RS4 FBSTABGM is not used.
Are you going to declare it useless, and "not meant to be used" as well? Wink
Yes because that's what it is.
That's one of the reasons why it is not in later systems like MED9.
You would not believe how much useless stuff is in a current software, that was used to fix a specific problem ages ago but is not used any more.

My point is to fuel constantly to preemptively decrease EGT. Not tune based on emissions, and then dump fuel when you reach a certain EGT setpoint, and then set lambda rich enough to hold a certain EGT limit.
If you tune for performance, not for emissions, it's just not the way to do things IMO, so obviously you end up using some things "not as intended".
I'm not sure why you think that emissions have to do anything with that.
Even on a FTP75 vehicles like a RS4 will not exceed 3500 RPM or more that half load.
LAMBTS is for component protection were it is needed nothing more. That's what it should be used for. For other fueling stuff LAMFAW has enough options to suit all needs
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silentbob
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« Reply #43 on: June 06, 2012, 10:55:46 AM »

Another question if I may..
EGT model.. and hardware effects on it... eg: higher flowing exhaust manifold, bigger turbos K04 vs GT35, very different scenarios.  do you say the vag egt model is equally valid between very different hardware setups?

I am trying to understand more about the me7 here.. please bare with me. thx

If you want a accurate EGT model you have to calibrate it for you specific hardware. Backpressure, ignition calibration s.o. all have a big influence.
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prj
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« Reply #44 on: June 06, 2012, 11:42:39 AM »

Sure you did. You said which results in excatly what I have said.
No, it does not result in what you have said.
I quote:
So in other words you say that the enrichment to reach a certain EGT is the same on all RPMs.
I don't know where you are reading this out from, but it's not the case at all. You assume I want to reach a certain EGT with LAMBTS, which I don't. Also, there is ATR.
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What you are trying to create here is a P controler. This will not work properly.
And why exactly? I've logged different gears on the local airfield with this approach, and it behaves exactly the way I want to.
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LAMBTS is for component protection were it is needed nothing more. That's what it should be used for. For other fueling stuff LAMFAW has enough options to suit all needs
So tell us how exactly you are going to use LAMFAW to run main fueling on a performance oriented car.
And I mean tuning an existing software when you can't compile what is needed from source.
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