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Author Topic: TABGSS vs modelled EGT  (Read 22566 times)
nyet
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« Reply #15 on: April 26, 2019, 03:08:13 PM »

That approach melts the engine on a bad tank of fuel, no thanks.

But it is no different than
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With FBSTABGM 0 the entire BTS function is disabled.
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prj
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« Reply #16 on: April 26, 2019, 08:10:25 PM »

But it is no different than
Hence both are a horrible idea.
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totti
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« Reply #17 on: April 27, 2019, 04:09:38 AM »

What could be the problem when it's not reach the required boost? Is it better when the required boost under the current?

It can't reach required pressure at high rpm either.

By and large, you should not let boost deviation happen, code or no code. That way if something goes wrong, it will be reflected in deviation.
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totti
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« Reply #18 on: April 27, 2019, 04:11:24 AM »

My mechanicher wanted to run from lamfa  not from bts. That's why we would like to use bts only what the EGT is too high.
I don't see a good reason for him to do this, since he can just adjust the BTS tables to do what he wants.

The question is why the onset is delayed so far above TABGBTS
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prj
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« Reply #19 on: April 27, 2019, 04:42:25 AM »

My mechanicher wanted to run from lamfa  not from bts. That's why we would like to use bts only what the EGT is too high.

BTS should almost always be always in use, but tuned so that it only kicks in with bad fuel or indeed when EGT is high.
Killing the entire thing until a certain temperature is a really bad idea, because by then it will be far too late. BTS is there to stabilize before it gets out of hand.
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totti
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« Reply #20 on: April 27, 2019, 06:07:10 AM »

I accept this. The problem is that the tabgbts is 730 celsius from the beginning. So I will always run from the BTS table with full throttle. I will check the EGT modell parameters. I don't know what could be the difference between the current model and the real EGT.

BTS should almost always be always in use, but tuned so that it only kicks in with bad fuel or indeed when EGT is high.
Killing the entire thing until a certain temperature is a really bad idea, because by then it will be far too late. BTS is there to stabilize before it gets out of hand.
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zweistein
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« Reply #21 on: April 27, 2019, 07:23:08 AM »

Set TABGBTS to 980 , then BTS will trigger when modelled EGT is above that value
there is also TKATBTS , set this to the same.  BTS will also trigger to protect the cat.

Modelled EGT comes from  KFTATM, so  put in lower values .
But KFTATM is for lambda = 1 at optimal iginition angle, there is corrections for richer lambda in  KFATMLA (so lower by 50-100 degrees for richer lambda) and other corrections for  non optimal ignition angles (KFATMZW)

Then there are several time constants that defining the transfer of heat to exhaust pipes / cat. Those dipend mostly on the gas flow.

Best is to measure EGT and put in measured values  into KFTATM to have a proper starting point.

Good luck



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prj
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« Reply #22 on: April 27, 2019, 12:19:13 PM »

Set TABGBTS to 980 , then BTS will trigger when modelled EGT is above that value
there is also TKATBTS , set this to the same.  BTS will also trigger to protect the cat.
980C is way too late. You realistically never want to exceed 1000C pre-turbo.

I accept this. The problem is that the tabgbts is 730 celsius from the beginning. So I will always run from the BTS table with full throttle. I will check the EGT modell parameters. I don't know what could be the difference between the current model and the real EGT.
730C is not on all the time, it will be on from only longer WOT runs where you need it... log your actual tabgm and so on.

There's a lot of basics missing here, a lot of suggestions without EVER asking "why?" or "how?".

An engine's ability to heat it's cylinders is directly proportional to the amount of flow through the engine. Until you get to very rich mixtures that help to cool.
That means that at 3500 RPM you are almost never going to actually have EGT problems vs. for example 7000 RPM. This is because the engine cylinders have twice as much time to cool between two power strokes, and there is also (very roughly, depends on curve) half as much fuel burned. So literally, as your RPM's go up your EGT gain increases very quickly, and as RPM's are lower it decreases quickly.

The same idea should be applied to BTS tuning. Tune it so that at lower RPM's it only actually kicks in if there is a bunch of timing retard. This can be controlled with the base delta and KFFDLBTS.
Other than that with normal fuel lambts should be very close to output from LAMFA throughout the range. Actually as EGT heats up, backpressure of exhaust gas also increases and there is more timing pull, so having KFFDLBTS at reasonable values will richen up your mixture as the engine gets hotter.
If you want some additional safety you can set FBSTABGM to be a little more aggressive after a certain temperature. For example 1.01-1.02 at 900C calculated and 1.0 below that.

Not using BTS at all or not using KFFDLBTS is a great way to melt the engine on part throttle on the autobahn when you are going fast, but you are not triggering LAMFA and running lambda 1 with a bunch of boost. Or if you get some bad fuel.

To do these things correctly at least some knowledge about the internal combustion engine process is required. I've seen outright ridiculous "advice" posted in this thread, which really makes me scratch my head...
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totti
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« Reply #23 on: April 27, 2019, 02:06:43 PM »

Thank you a lot for this summary. What is the diff between tabgm and tabgbts? I've just realized now that I'm log only the tabgbts value currently. Which is the trigger value for BTS table?

980C is way too late. You realistically never want to exceed 1000C pre-turbo.
730C is not on all the time, it will be on from only longer WOT runs where you need it... log your actual tabgm and so on.

There's a lot of basics missing here, a lot of suggestions without EVER asking "why?" or "how?".

An engine's ability to heat it's cylinders is directly proportional to the amount of flow through the engine. Until you get to very rich mixtures that help to cool.
That means that at 3500 RPM you are almost never going to actually have EGT problems vs. for example 7000 RPM. This is because the engine cylinders have twice as much time to cool between two power strokes, and there is also (very roughly, depends on curve) half as much fuel burned. So literally, as your RPM's go up your EGT gain increases very quickly, and as RPM's are lower it decreases quickly.

The same idea should be applied to BTS tuning. Tune it so that at lower RPM's it only actually kicks in if there is a bunch of timing retard. This can be controlled with the base delta and KFFDLBTS.
Other than that with normal fuel lambts should be very close to output from LAMFA throughout the range. Actually as EGT heats up, backpressure of exhaust gas also increases and there is more timing pull, so having KFFDLBTS at reasonable values will richen up your mixture as the engine gets hotter.
If you want some additional safety you can set FBSTABGM to be a little more aggressive after a certain temperature. For example 1.01-1.02 at 900C calculated and 1.0 below that.

Not using BTS at all or not using KFFDLBTS is a great way to melt the engine on part throttle on the autobahn when you are going fast, but you are not triggering LAMFA and running lambda 1 with a bunch of boost. Or if you get some bad fuel.

To do these things correctly at least some knowledge about the internal combustion engine process is required. I've seen outright ridiculous "advice" posted in this thread, which really makes me scratch my head...

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totti
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« Reply #24 on: May 12, 2019, 11:39:59 AM »

Hi,

What is the difference between the tabgm and tabgbts? I've logged these and there is 150-200 celsius difference. Which is the input for BTS tables?

Thanks
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nyet
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« Reply #25 on: May 12, 2019, 07:18:57 PM »

I kept telling you this over and over again.

Not sure why you ignored me.

https://s4wiki.com/wiki/Tuning#LAMBTS
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totti
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« Reply #26 on: May 13, 2019, 01:30:48 PM »

Thanks. So tabgbts_w is the input. But what is the difference compare to tabgm_w? I don't have EGT sensor at my car but tabgbts values are very high. I've checked tabgm and it shows more realistic values.

I kept telling you this over and over again.

Not sure why you ignored me.

https://s4wiki.com/wiki/Tuning#LAMBTS
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nyet
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« Reply #27 on: May 13, 2019, 06:34:02 PM »

Your question really should be what is the difference between tabgm_w and tabgkrm_w, since SYTURBO and CWLAMBTS.2 select which one ends up in tabgbts_w

I don't know what the difference between the two EGT models are. The FR has more details but I've not looked more closely.

Looks like kr stands for "Krümmer". No clue what elbow that is referring to.

TABGKRM_W ATM AUS Abgastemperatur im Krümmer aus Modell
TABGM ATM AUS Abgastemperatur vor Kat aus Modell
« Last Edit: May 13, 2019, 06:40:59 PM by nyet » Logged

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totti
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« Reply #28 on: June 30, 2019, 08:23:01 AM »

Hi,

I've tried to find a lot about BTS tables. proj said that FBSTABGM 0 disable the BTS. I've checked my original software and FBSTABGM is 0 at 920 celsius. Does it mean that until 920 celsius the BTS is disabled?
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nyet
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« Reply #29 on: June 30, 2019, 03:33:28 PM »

Hi,

I've tried to find a lot about BTS tables. proj said that FBSTABGM 0 disable the BTS. I've checked my original software and FBSTABGM is 0 at 920 celsius. Does it mean that until 920 celsius the BTS is disabled?

Yes
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Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
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