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Author Topic: only manipulating LAMFA?  (Read 36209 times)
AndiS4
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« Reply #15 on: August 08, 2012, 09:12:51 AM »


egt nearly always exceed 500°C...

In all stock S4 tabgbts is set at about 500°C..

This would mean it would always run in lamBTS using kflbts.

Then Bauteilschutz isn correct as a declaration of this part of function imo.



 
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RS4boost
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« Reply #16 on: August 08, 2012, 09:59:36 AM »

I believe, you talk about two different things.

The measured 980 °C from the "TABGSS(2)" value is only the desired exhaust gas temperature for the EGT regulation.
It is the max. temperature target and not the starting point to run with LAMBTS.
If the 980°C thresold value is reached, the ECU will run additionaly the delta lambda mechanism "KFDLBTS" and "KFFDLBTS" to make a richer AFR.

At the internal modeled EGT threshold "TABGBTS" (S4= 500 °C, RS4=750 °C), the ECU runs with "KFLBTS".
The only exception is when the "LAMFAW" value is richer then the "KFLBTS".
In this case the ECU will run with KF "LAMFA" and not with "KFLBTS".

To run with a richer AFR makes sense to work against a high EGT.
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nyet
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« Reply #17 on: August 08, 2012, 10:39:57 AM »

egt nearly always exceed 500°C...

No, it DOES NOT. Please reread the EGT article. AGAIN.
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AndiS4
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« Reply #18 on: August 08, 2012, 10:58:51 AM »

I m sure rs4boost and me are right.

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nyet
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« Reply #19 on: August 08, 2012, 11:03:30 AM »

I m sure rs4boost and me are right.

rs4boost is right, you are wrong. There are two EGT temps, one is modeled, one is measured.

TABGBTS has nothing to do with the measured EGT.

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phila_dot
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« Reply #20 on: August 08, 2012, 02:49:46 PM »

If the 980°C thresold value is reached, the ECU will run additionaly the delta lambda mechanism "KFDLBTS" and "KFFDLBTS" to make a richer AFR.

This is not true.

[KF]DLBTS and KFFDLBTS are only used to offset Lambda for degraded ignition angle in BTS.

Lambda intervention from actual EGT is calculated in ATR and executed via dlamatr_w. In limp mode Lambda offset is calculated from DLAMTRNLN. During normal EGT regulation it is calculated using PID control based on TABGSS and tabg_w delta.
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RS4boost
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« Reply #21 on: August 08, 2012, 04:21:19 PM »

This is not true.

[KF]DLBTS and KFFDLBTS are only used to offset Lambda for degraded ignition angle in BTS.

Lambda intervention from actual EGT is calculated in ATR and executed via dlamatr_w. In limp mode Lambda offset is calculated from DLAMTRNLN. During normal EGT regulation it is calculated using PID control based on TABGSS and tabg_w delta.

Yes, you are absolutly right.

I have just looked up the "ATR" description at the ME7.1 Funktionsrahmen on page 406.

The additionaly delta lambda mechanism is a PI regulation (P=ATRP / I=ATRI) with an influence to lambda over dlatr_w with a maximum of LATRO and DLATRMN.
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nyet
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« Reply #22 on: August 08, 2012, 05:06:11 PM »

Thanks guys. I will update the EGT wiki entry time permitting.
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AndiS4
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« Reply #23 on: August 09, 2012, 12:12:58 AM »

Ok, great! learned a lot!

I was also wrong with the modeled EGT with beeing interpolated.
Its calculated in ATM 33.50.

When I have some more time, ill try to find out, how fast tabgm reaches the s4 treshold of 500°C.

Did anyone log tabgm?

So to the topic, regarding tabgm_w (modeled) and the point it exceeds tabgbts, gives us an area, where we have to work out a proper transition.

Imo only tuning lamfa (eg to 0,83 lambda) doesnt make sence, because while exceeding tabgbts with stock lambts table, in several areas, its too lean. Therefore "tuned"  Lamfa might be richer and as result requested AFR stays at lamfa. This would run, but efficiency (fuel economy) is messed up.   

regards
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nyet
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« Reply #24 on: August 09, 2012, 08:02:43 AM »

All of this is covered in depth in the various fueling discussions here and in the s4 wiki.

thread:
http://nefariousmotorsports.com/forum/index.php?topic=141.msg9699#msg9699

LAMFA vs LAMFAWKR vs LAMBTS:
http://s4wiki.com/wiki/Tuning#Open_loop_AFR

Did anyone log tabgm?

yes

Quote
Imo only tuning lamfa (eg to 0,83 lambda) doesnt make sence, because while exceeding tabgbts with stock lambts table, in several areas, its too lean. Therefore "tuned"  Lamfa might be richer and as result requested AFR stays at lamfa. This would run, but efficiency (fuel economy) is messed up.

I can't make head or tail of this.
« Last Edit: August 09, 2012, 08:46:51 AM by nyet » Logged

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AndiS4
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« Reply #25 on: August 13, 2012, 02:37:57 PM »

Regarding to the topic the answer makes sence. I dont know why its not clear that only changing lamfa into richer doenst make sence at an s4 with a stock lambts.

If i am wrong, i would be very interested wich positive affect changing lamfa an leaving bts stock would have except making fueling more predictable. For me there isnt any technical positive point.

Youre right by saying it is discussed in several other topics, but i just wanted to help with an answer at this topic here.

Regards



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nyet
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« Reply #26 on: August 13, 2012, 05:31:05 PM »

You answer makes no sense because it doesn't matter if modeled EGT goes over TABGBTS.

If LAMFA is leaner than BTS, that is what req AFR follows.

Please don't post misinformation!

That said, stock BTS is a bit rich in high load regions, and might have to be dialed back if you are attempting a LAMFA only tune.
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AndiS4
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« Reply #27 on: August 13, 2012, 10:55:09 PM »

What misinformation?

After exceeding tabgbts, the richer value of lamfa or kflbts will be choosen.

But eventually we only talk past each other. I consider not only the increase in power. The efficiency is also important to me. Here it is necessary to apply a good transition from lamfa to the component protection with reasonable values.  Changing only Lamfa into rich (eg 0.83),the efficiency would deteriorate significantly. But My opinion is, that enriching towards a powerful 0.83 or whatever you wich can be made nicely by using lamfa and kflbts together with a nice transition towards eachother.

And in my case modeled egt is always exceeding (in every wot pull) tabgbts´ 500°C.  (at least over 3000 and a bit rpms at 3rd gear)


 
« Last Edit: August 14, 2012, 12:33:00 AM by AndiS4 » Logged
nyet
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« Reply #28 on: August 14, 2012, 11:34:51 AM »

Here it is necessary to apply a good transition from lamfa to the component protection with reasonable values.  Changing only Lamfa into rich (eg 0.83),the efficiency would deteriorate significantly. But My opinion is, that enriching towards a powerful 0.83 or whatever you wich can be made nicely by using lamfa and kflbts together with a nice transition towards eachother.

This sounds good to me.  I couldn't figure out your previous posts, but this one gets it right, IMO.
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AndiS4
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« Reply #29 on: August 14, 2012, 11:54:50 AM »

thanks.
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