NefMoto

I'd like to be able to set a boost profile that is flat or increasing even, but I'm not exactly sure how to.

The attached log and graph is pretty much what I see every time, so I have to make odd adjustments to LDRXN and then make PID adjustments to keep the boost below the peaks and dips of the req. boost line.

How is ME7 coming up with the req. boost curve?  And how do I change it to something like a flat boost req. (or increasing)?  Is there a map that converts boost > load or vice versa?

Thanks!

I would like to know this one too!!
I had an ugly boostovershoot on mine, cousing TC, but i sorted it out with DIMX. It took me like 10 revisions, but it looks pretty good now.

KFURL/KFPRG

Are what I believe you are referring to.

I don't really have an issue with overshooting, the boost is where I want it.

what I don't understand is how to make requested boost what I actually want it to be.  I know that cam changeover, etc on the S4 plays a role in cyl filling but I still don't get why it spikes or tapers the req boost.  I'd like to run say 22 psi to red line, but to do that now I'd have to bump LDRXN in various places to make sure I can run that boost profile without overshooting the requested too much and going into limp/getting TC.

That is the conversion from load to pressure and the answer to his question, but won't help achieve his goal.

http://nefariousmotorsports.com/forum/index.php?topic=3978.msg40306#msg40306

vpsspls_w - KFVPDKSD / KFVPDKSE
fpbrkds_w - KFPBRKNW / KFPBRK

If you want a clean boost req you have to hack the req load->pressure path.

I would start by logging the 5 variables that determine requested boost pressure to determine what and why it is causing the fluctuation.

Then you can decide if you want to make a change and where it should be applied.

I'll be honest I have no idea what the 5 variables would be.

Worst part is, this (similar) issue happens to me in my 1.8T as well...

I feel I'm the only one that's having issues like this around here (that's how it feels anyway) while everyone else seems to be able to dial in a boost req. correctly, yet on 3 separate cars in the last little while (including my 1.8T) none of what is happening here makes any sense to me.  My 1.8T (w/ K04) is by far the worst offender of not doing what I tell it to.  Seemingly completely ignoring KFLDIMX, etc..

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 :)

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.

ME7 is a torque based system.
Who cares what the boost is? You are targeting a certain cylinder filling, in cold weather you need more boost, in hot weather less boost to accomplish the task. Also, you need different amounts of boost at different rpm.
The reason it is making your life so difficult, is because you are not doing what is intended.

That said, if you want to have flat boost request, just leave all the other maps, set LDRXN high and limit load through KFLDHBN (which is pressure ratio).

rlsol will still be subject to the same influences. The output gets converted to load and would then potentially become rlsol. It is then subject to the same calculation and influences en route to plsol.

CAUTION! HACK!

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

The notch is a clear indication that KFNW needs work.

True, I suppose my frustrations get the best of me sometimes.  PRJ (or anyone) if you had a min to look @ the .csv and let me know if you see anything out of the ordinary?  Or maybe that I should be changing my way on going about tuning ME7?  I'd be more then happy to email the file that goes along with that log.

I suppose my main issue with all this is there's so much going on, things can get tedious sometimes with the constant logging/reading/flashing cycle that can easily eat up a few hours of time for just a few minor revisions.  Compared to live tuned systems with live data (stand alone) that I'm normally used to getting direct results.

If fixing the notch is only about playing with the cam on/off and/or cylinder fill compensation then I will give that a try.  Otherwise I'll just tune around it I suppose.

I would be really curious on how to get ME7 to accept an increasing boost (keeping TQ flat) model as well, has anyone ever thought about it?  Of course normally cylinder filling/VE drops after peak TQ and adding boost is a fantastic way to keep an extremely linear TQ curve after peak.  I"m assuming this would require more then just having LDRXN end up at some retarded high figures?

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.

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?

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.

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.

If you don't want boost to taper, then you need to request more load.

^^ 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?

TTT, I'd like to continue this discussion :)

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. :)

Here is a better after log.

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.

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


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 :)

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..

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 :)

Technically, HBN is safer.

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. :)
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.

I would tune KFMIRL/LDRXN for desired boost profile and tune KFLDHBN so that ldrlts_w is just above rlmxko_w at sea level.

(http://i1360.photobucket.com/albums/r658/Lion_32/Chargelimit_zps5cb9df6c.png)
(http://i1360.photobucket.com/albums/r658/Lion_32/HBN_zpsab56e55e.png)

What do you make of it?
It looks good to me

ldrlts_w directly relates to my HBN???

Bump on the HBN map

This is  colant temp or IATs vs rpm axes.
Output should be absolut pressure.
Now, HBN is max pressure for altitude limitation.
I need to clear this up.

If we take 6000rpm at 100deg F or C??
Does the output value means that car should not boost more then 1.1 bar = 16 psi??
At what altitude in that case??

Everything in motronic is always C


Please, step back and do some reading on turbos :/

Specifically, pressure ratio :(

At that point it says 2.09, what does it mean exactly?
Why cant you give me a straight answer, please. It was a straight forward question.

He did. It's a ratio. If you know atmospheric pressure, you can plug it in to get maximum allowable boost.

Thank you!!!
This is what i was after.
It explains everything.
I was on to it.
Atm pressure is 983mbar here
0.983 x 2.09 is about 2.1 bar absolut, which gives us 1.1 bar of boost or 16psi.
That should be just right??

Very old thread...

I am trying to understand why my plsol is like it is. This thread does not contain useful information about 1.8t me7.5 i think.
Will try to log with vvt on/off over the whole rpm range. Maybe some 1.8t guy knows what to touch? my HBN is maxed, LDRXN is my limitation.

What do you think is wrong with it? You didnt post any logs or any rationale. Requested load is covered extensively in the s4 wiki tuning page.