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Author Topic: How to make sense of and set a good boost profile  (Read 10154 times)
jibberjive
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« Reply #15 on: February 27, 2014, 04:38:09 PM »

For 2.7t ME7.1, this is all you need:

http://s4wiki.com/wiki/Tuning#Cam_changeover_effect_on_requested_boost

not sure about 1.8ts

NOTE IT IS A HACK.

I'm sure prj (or others) can tell you why it isn't the right thing to do Smiley

There is a list of maps, but nothing on what to do with them. If we can reach a consensus, I will summarize it and write it up for future generations.

Yeah, though those maps may have worked, there are no application notes, and those 4 maps are definitely not the consensus way to approach it (if there were a 'consensus').  I think that is one section of the wiki that could definitely benefit from maybe a little focused community effort to express the best practices with the notch.
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nyet
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« Reply #16 on: February 27, 2014, 04:53:17 PM »

Fixing the notch is easy and none of those maps need to be touched.

The notch is a clear indication that KFNW needs work.

In particular, you mean don't let the cam changover occur in areas where you don't want the req boost bouncing around?

The stock KFNW has a transition at 3600-3800 at load>=120.. are you suggesting moving the transition to a lower rpm?

or something else?
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phila_dot
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« Reply #17 on: February 27, 2014, 05:35:57 PM »

Changeover from advanced to retarded needs to be at a higher RPM.

It's obvious if you overlay logs locked in each state.

To be clear, I'm responding specifically regarding the notch.
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ddillenger
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« Reply #18 on: February 27, 2014, 05:48:16 PM »

Whenever I get a notch, I look to make sure I didn't make changes to KFPBRKNW or KFPBRK and forget about it. Making sure the last columns are the same has always been the solution I've used.

HOWEVER, I really don't think NVR was talking about a notch, but rather his boost curve tapering off when LDRXN was flat.
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phila_dot
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« Reply #19 on: February 27, 2014, 06:18:01 PM »

If you don't want boost to taper, then you need to request more load.
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NOTORIOUS VR
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« Reply #20 on: February 28, 2014, 06:15:37 AM »

^^ Fair enough, it's clear I was too fixated on boost curves instead of TQ/load, so increasing the load request makes sense.

As for the notch/bump, it doesn't bug me unless it causes and under/over boost issue (which it's not at this point), but I will say that I've been thinking of playing with the cam position since with bigger turbos you can get a little more out in the mid range much of the time.

That said, the modifier maps to correct combustion efficiency seems to be only for the cross-over point (ie when the cams are moving) is this correct?

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NOTORIOUS VR
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« Reply #21 on: March 04, 2014, 06:23:03 AM »

TTT, I'd like to continue this discussion Smiley
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chokee
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« Reply #22 on: September 22, 2014, 12:25:00 PM »

I have my cam switchover set to occur at 4400rpm via KFNW. I had a huge notch in requested boost at about 4600-4700rpm about 1.5psi drop. All around my boost would vary about 2psi between 3000rpm and 7k rpm.

I just used the hack nyet posted on my M-box for maps KFURL, KFPRG, KFPBRK, KFPBRKNW. After using this hack my requested boost notch is gone and overall my requested boost almost a straight line between 3k and 7k rpm.

Thanks.

ps. Yes, my KFLDIMX needs work. Smiley



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chokee
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« Reply #23 on: September 22, 2014, 12:29:03 PM »

Here is a better after log.

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phila_dot
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« Reply #24 on: September 22, 2014, 04:47:34 PM »

The problem with that is you are not actually fixing anything.

The notch is there because you need more boost to meet target load after changeover.
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nyet
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« Reply #25 on: September 22, 2014, 04:58:01 PM »

The problem with that is you are not actually fixing anything.

Agreed. Whether or not req boost has a notch has nothing to do with the problem you are trying to solve

Quote
The notch is there because you need more boost to meet target load after changeover.

The problem is, the VVT guys didn't talk to the PID guys -- so in reality, the idea that the PID can accurately track a rapidly changing req boost due to changing VE/CE is a fiction Smiley

And in the stock operating range the notch is almost imperceptible. At 15+ PSI it becomes noticable... and there is absolutely NO gain in moving the req boost around so much. Zero.

Now, you could argue there are other places where the VE correction is relevant, and flattening the VE tables is a bad idea... can't argue with that. Would be nice if req boost could be hacked to just ignore the VE table, while everything else stays the same.. imo varying boost really isn't relevant and only causes PID problems when the set point has large discontinuities.

All my 2 cents of course.. I could be very wrong..
« Last Edit: September 22, 2014, 05:00:17 PM by nyet » Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

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 experience.
Lost
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« Reply #26 on: September 22, 2014, 11:33:16 PM »

However if we would summaries all of this PRJs approach is easiest?
Just bump up the LDRXN and cap it with HBN?
Can it be done the other way around?

BC where I live HBN does not have any affect - at sea level.
Can't we just bump up HBN, and regulate our req load/boost with LDRXN?
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nyet
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« Reply #27 on: September 23, 2014, 09:27:43 AM »

However if we would summaries all of this PRJs approach is easiest?
Just bump up the LDRXN and cap it with HBN?
Can it be done the other way around?

BC where I live HBN does not have any affect - at sea level.
Can't we just bump up HBN, and regulate our req load/boost with LDRXN?

Either approach is fine Smiley

Technically, HBN is safer.
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ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

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 experience.
phila_dot
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« Reply #28 on: September 23, 2014, 09:54:35 AM »

However if we would summaries all of this PRJs approach is easiest?
Just bump up the LDRXN and cap it with HBN?
Can it be done the other way around?

BC where I live HBN does not have any affect - at sea level.
Can't we just bump up HBN, and regulate our req load/boost with LDRXN?

What do you mean by easiest?

How does being at sea level make a pressure ratio limit ineffective?

Both maps should be tuned. LDRXN is you max requested load that will be followed when the conditions are right. KFLDHBN is the max pressure ratio limit. This keeps thing in check with changing altitude.

The idea is for the car to perform consistently and exceptionally regardless of conditions. That is why ME7 is as complex as it is and all of these maps are available.
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Lost
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« Reply #29 on: September 23, 2014, 10:29:27 AM »

What do you mean by easiest?

How does being at sea level make a pressure ratio limit ineffective?

Both maps should be tuned. LDRXN is you max requested load that will be followed when the conditions are right. KFLDHBN is the max pressure ratio limit. This keeps thing in check with changing altitude.

The idea is for the car to perform consistently and exceptionally regardless of conditions. That is why ME7 is as complex as it is and all of these maps are available.

Easiest - most simple - you choose. Smiley
We are at see level, and there is no much altitude in Sweden at all.
Driving on e85 around the year, keeps the car in country.
I got a couple of DDs for driving outside of Sweden.
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