NefMoto

So the notch from NWS cam switchover has been talked about in part in different threads on here, but I haven't necessarily seen explicit input on how people have been tweaking the maps to overcome the notch in load/boost/fueling that often occurs.  I haven't seen much about what people have actually found out about this, just some vague references that they were able to work it out.  Here's some of the input that I have seen so far:

S4 wiki (http://s4wiki.com/wiki/Tuning#Cam_changeover_effect_on_requested_boost) - maps relating to this are
    KFPBRK - Correction factor for combustion chamber pressure
    KFPBRKNWS - Correction factor for combustion chamber pressure when NWS active
    KFPRG - Internal exhaust partial pressure dependent on cam adjustment when sumode=0
    KFURL - Conversion constant for ps->rl dependent on cam adjustment when sumode=0

And I will add these two maps as relevant:
    KFNW - Characteristic map for variable camshaft spread
    KFNWWL- Timing for variable cam, warmup


Phila Dot says:



NotoriousVR says:


Here's his log with the notch gone in boost, and the notch in load calmed for the most part:



As for my input, I've played around just a little bit with it with a little success, but haven't had time to iron it out and I'm not sure the best way to go about it yet.  Some things to note on my setup: GT turbos, 2.8l heads & cams.  Here is the notch in my logs as I make some slight tweaks to the cam switchover maps (the 6 maps referenced above) between revisions:

File #1 - Stock settings on all cam switchover maps, you can see the notch is in load (rl_w), MAF, injector, and in my actual AFR between 3800-4100RPM it shoots sharply down rich (I've verified that this has nothing to do with any of the MAF/fueling maps and is almost surely from NWS):

(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/CamSwitchover_Stock.jpg)
(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/GT146_2FATS_VE_OLD_20120420_043110-FuelInjector.png)
(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/GT146_2FATS_1_vs_GT146_2FATS_2_vs_GT146_2FATS_VE_OLD_20120420_043110-LoadMAF.png)
(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/GT146_2FATS_1_vs_GT146_2FATS_2_vs_GT146_2FATS_VE_OLD_20120420_043110-Fueling.png)


File #2 - On the advice of Phila_dot, I tweaked KFPBRKNW a little; in the last two load columns of the 3800 RPM row (the 140% & 170% load columns, as that is what load I was above in 3rd gear WOT, per the previous logs) I raised the value from 1.075 to 1.11.  You can see it subdued the magnitude of the load notch for sure, but it looks like it introduced a requested boost notch from 3500-4000. The actual AFR notch is helped a little.

(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/CamSwitchover_GT147.jpg)
(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/GT149_2FATS_1_vs_GT149_2FATS_2_vs_GT149_2FATS_VE_OLD_20120420_062625-FuelInjector.png)
(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/GT149_2FATS_1_vs_GT149_2FATS_2_vs_GT149_2FATS_VE_OLD_20120420_062625-Fueling.png)
(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/GT149_2FATS_1_vs_GT149_2FATS_2_vs_GT149_2FATS_VE_OLD_20120420_062625-LoadMAF.png)


File #3 - Thought I'd try to go the direction that NotoriousVR was suggesting, and set the "cam profile map" to all 1.  He said maps, as in plural, and I wasn't sure exactly which maps he was talking about, so I thought I'd give KFPBRK a try at all 1's. This didn't seem to help any. Also, don't pay attention to the boost overshoot or the lean top end AFR, those are due to other unrelated tweaks.  The AFR around 3800-4100 is still a funky shape.  There seems to be an irregularity with requested boost here as well, and I'm not sure how much of it is related to my changes in the boost stuff or the changes in cam switchover, but it looks like at least some of the weirdness around 3800-4100 can likely be attributed to the cam switchover.

(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/CamSwitchover_GT148.jpg)
(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/GT148_2FATS_1_vs_GT148_2FATS_2_vs_GT148_2FATS_VE_OLD_20120420_061037-LoadMAF.png)
(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/GT148_2FATS_1_vs_GT148_2FATS_2_vs_GT148_2FATS_VE_OLD_20120420_061037-Fueling.png)
(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/GT148_2FATS_1_vs_GT148_2FATS_2_vs_GT148_2FATS_VE_OLD_20120420_061037-FuelInjector.png)



So, here are some questions/thoughts that I have (any input/discussion is encouraged):

1. In the S4 wiki it says, "abrupt changes in requested boost near the MAP limit can make the boost PID unhappy."  I'm only boosting ~15.5 psi, so I'm nowhere near the MAP limit.  How relevant is the MAP limit to this discussion?

2. Has anyone played around much with KFNW/KFNWWL, and what has been your results (Julex?)?  We can't look into the RS4 files for any insight into 2.8 cams or bigger turbos, as they have a completely different KFNW/WL scheme, with many maps we don't have.

3. NotoriousVR, which maps specifically are you setting to 1 to cure the requested boost part?

4. If fnwue dropping from around 1 to around 0 is indicative of it being a cam switchover issue, what behavior would fnwue ideally have?  It's got to drop to around 0 when NWS is activated, no?

5. Obviously the load notch and requested boost notch are related, but it seems that what fixes one may not necessarily fix the other.

6. KFPBRK/NW have pretty poor RPM resolution up around where the notch is for my turbos (3000, 3800 and 5000 are the RPM rows, whereas down lower in the rev range the rows are separated by 250-500 RPM). Any thoughts on possibly changing the axis for better resolution up there, or bad idea because the resolution is needed down low?

7. The biggest question of all, WHAT SPECIFICALLY HAVE YOU DONE TO FIX THE LOAD AND/OR BOOST NOTCH IN YOUR OWN FILE?  WHAT HAVE YOU FOUND WORKS, OR WHAT HAVE YOU FOUND DOESN'T WORK? (and make note of what setup you're running)

I have modified ONLY the maps mentioned in the s4wiki, and i don't have a notch for req boost, act load, or req load.

However, with those maps STOCK, my car was not exhibiting the notch you see in MAF.

I think the notch in your MAF readings are the source of your issues.

All four KF maps you grouped below are used to calculate amount of residual cylinder pressure dependent on NWS state and is directly then used to calculate load and (I think) maf voltage to g/s conversions. Log MAF sensor voltage and you will see that there is no notch there....

To be honest I don't exactly remember what I did but it was hackish. I would like to see if anybody has ideas on that. Oh... and this doesn't show when you run underscaled maf.

Hi jibberjive.

This is an interesting thread from my perspective because this notch is (and always has been) clear in my logs/dyno trace pre- and post Revo remap and I recall speculation on it in the context of camshaft switchover from the TT Forum. Since nobody there (except the odd tight-lipped pro-tuner) had any knowledge of those maps and constants that influenced NWS, I always wondered what was truly causing it. For me, the trough is at approximately 3,250 rpm but the 'pulse width' of the notch spans roughly 3,000 to 3,500 rpm give or take 100 rpm.

Because I don't tune, my contribution is limited to some thoughts based on 1.8T engine variants: In the case of binary adjustment, the factor fnwue governs continuous switching between the maps KFZWOP and KFZWOP2, so clearly a binary adjustment is likely to be relatively abrupt if there is any 'abrupt' change in the optimal ignition angle between KFZWOP and KFZWOP2. There is some difference between engine speed points 3,000 and 3520 on my stock tune (12 to 17 degrees at zero load decreasing to only 0 to 1.5 degrees difference at load points 155%, 175 and 191%) so not enough at higher loads to constitute an 'abrupt' change, I suggest.

Also, there is some correction being applied via KFPNRKNW which I suppose you could dial out by setting it it to 1 but it seems to me that the dip I observe is large enough to be considered sufficiently gross to consider increasing KFMIRL in that region to try to offset it? In fact, when I examine my stock KFMIRL, I see an increase at the intermediate speed point 3520 rpm for the requested torque range 45% to 90%. Could this be evidence that the OEM calibrator has indeed tried to dial out this phenomenon by increasing KFMIRL (but not enough?)

TTQS

The factor fpbrkds_w for the calculated combustion chamber pressure prb_w is calculated from KFPBRKNW and KFPBRK.  pbr_w is the main input for rl_w.

fpbrkds_w is (1 - fnwue) * KFPBRK + (fnwue * KFPBRKNWS).

In my opinion, smoothing this transition will correct this.

The other maps that have been mentioned regarding this are not actually influenced by cam changeover. The bit b_nwvs is set if SY_NWS > 0.

If the notch was the result of a torque function (i.e. KFZWOP(2)) it would manifest in target load not actual.

So for my application, how would you suggest going about smoothing that transition, considering that where the notch is there's very little RPM resolution (3000, 3800, 5000)?  I raised KFPBRKNW in 3800 RPM in the two highest load rows in file #2 graphed above, and you can see it tamed it a little, so maybe raise it a little more there and lower it a little in the the 3800 RPM/high load columns in KFPBRK?  What do you think about the requested boost notch that that introduced when I raised KFPBRKNW?

I don't actually think it matters much if there is a notch in actual load on cam changover. In fact, it may be accurately modeling load anyway (which is probably what you want).

Unless, of course, you are logging fueling numbers you dont like (via wideband, not IDC or on time) ... as in the OP, who was seeing some odd wideband numbers near the cam changeover point.

My issue (as described in the wiki) was a notch in requested BOOST, which (as I said) was very problematic for the PID near the MAP limit, and particularly in the region where there is the most amount of wg change activity (peak boost)

If we do solve the fueling problem, somebody remind me to update the wiki :)

After looking again, KFPRG and KFURL are affected by cam changeover and effect rl_w.

I'll see if I can get some of these variables to log.

What do you think about my situation, where a notch in requested boost was introduced when I have 0% WG DC and am well below the MAP limit?

If your turbos spool sufficiently slow enough in ALL situations (i.e. you never see peak boost before cam changeover), then I don't think its an issue, unless you find your req boost aesthetically displeasing :)

ETA:

Also, if you are running openloop WGDC (to run over the MAP limit) then obviously a req boost notch means nothing :)

I was hoping more for some input on your thoughts of how the notch correlates with the MAP limit/WGDC, as my file takes those out of the equation. Trying to figure out the base cause and solution of the notch in general.

It affects requested pressure since residual pressure remaining in the combustion chamber WHEN NWS IS ACTIVE must be taken under consideration when stuffing more air in. Basically, with NWS active, there is some air left in the combustion chamber after the cycle. Requested pressure/air amount is then lowered by this remaining air in chamber. This lowered air coming in plus what's left in the cylinder will add to the amount of air (and therefore boost pressure) the system would request with NWS inactive.

I remember what I did in my tune. I disabled NWS at the highest load point for two last RPM thresholds it is active in stock tune. The other way to go about it would be to massage conversion tables you listed above, after studying FR naturally, so that the system doesn't change perceived load and adjusts boost accordingly when NWS is indeed active.

Which brings us to this:

On cam changover, it appears as though there is a discontinuity in the MAF readings. I am assuming that is because the amount of air being injested REALLY does change at that point.

So there are probably two different corrections that are happening

1) correct rl_w as calculated from MAF based on cam position
2) correct plsol as calculated from requested load on cam position

Is it possible to override 2 (deliberately) without screwing up 1?

AND

Is there an additional requested load correction based on cam position?

How did you go about that, with KFNW/WWL?

And the notch at 4k is even visible here in APR stage 2 logs: http://www.audizine.com/forum/showthread.php/482031-devils-own?p=7520007&viewfull=1#post7520007

On a side note could this Cam switch over be related to surge in anyway? I ask this as I can induce/ get surge without any problem below 4k, above 4k regardless of boost, surge just isn't present or a problem. Oddily when looking at my logs the Surge always goes at the same point it's as though a switch is turned and the surge goes around 4k. Now I'm having to hold back the boost to 18psi till 4k then I can ramp it up to what ever in need, having read this thread it just got me wondering if this camchange over is related or coincidence.

How much change over degrees occur?

Forget now but 18 or 21... A lot.

correct. 1 = active, 0 = inactive for a given rpm/load point.

Wow 18-21 degrees? That's major!

I hope you're not confusing timing advance with change in intake cam phase :).

When NWS activates, the intake cam advances forward causing the intake valves to open sooner but at the same time close sooner as well. In that state, the intake cycle overlaps exhaust cycle by quite a lot causing some exhaust gas to remain in the cylinder.

Timing advance is completely unrelated to this and stays roughly the same regardless of NWS active or not.

Ha ha no not timing advance, that would be crazy. I'm was referring to valve over lap.
18 degrees is a lot of advance when you consider normal turbo cams have no overlap.

Have you not looked at KFZW/KFZW2?

Yes I am familiar with the maps and I know what they are used for. I was referring to the fact that ignition doesn't advance by 18/21 (whatever the real cam advance is) degrees. Thanks for picking on it :)

Notice there is no notch in req load.

APR is most likely running a stock KFPRG/KFURL

I know, just picking. :)

I try to keep things clear for those that don't know.

I have no notch in requested load in mine either.  Also, I'm running a stock KFPRG/KFURL.

KFPRG/KFURL introduce the notch in req boost, not req load.

Your post that I quoted said "notice there's no notch in requested load,"  so I was just commenting that there's also no notch in my requested load, and I'm running those same stock maps as well.  It doesn't seem that my issues have much to do with requested load. 

So are you saying that after one fixes the load notch somehow, to fix the boost notch they should try massaging the KFPRG/KFURL? Any thoughts about how you would attempt to massage those if so (possibly raise the values slightly in the 3800RPM columns in the 18 and 30.5 degree rows)?

Taken from your first post, how, specifically, did you edit those maps that you mention?

Has anyone (besides Julex, and Nyet [but not with the MAF notch]) honestly never had this notch and overcome it?  If so, how did you go about it?  I remember seeing more than a few comments around of "yeah, we figured out the notch," but it seems like those people aren't interested in posting in this thread.

KFNWSE -Map for cam change over intake

This map runs from -4 below 4750 to 18 above is this the actual cam angle?

Another random thing I noticed, in KFNWWL there seems to be a discontinuity in two of the higher load columns where it goes from active (1) at low RPM's, to 0, then back to 1 at mid RPM's.  See the 110% and 135% rows that I circled in the pic below. Is there a reason for this, or do you think it's just an oversight by the factory, and those 0's in the middle should be 1's? If you look at the rest of KFNW/WL, there's a pattern of solid blocks of staying on, then switching off, not this on-off-on.

(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/CamSwitchover_Stock-1.jpg)

(http://i297.photobucket.com/albums/mm235/jibberjive/Logs/Notch/CamSwitchover_Stock.jpg)

honestly i think all of these tables in debate need to be stitched together to replicate what the ECU actually sees.  for instance, KFZW+KFZW2+KFNW = zwgru?  or whatever it is...     i asked this question before and there wasn't a very good answer.  how do the actual transistions occur?

is the 0-1 turned into a step function?  or is it a hard 0-state 1-state.   at what exact point does this transition occur relative to KFNW?
i think we need to take the s4 and rs4 zwgru and compare them.  all of the tables are vastly different.  i bet you'll see the timing reflects a physical change in the torque curve.  and now we're back to the torque model...

someone needs to take the tables we have and create an excel or matlab model of the expected torque curve, resultant horsepower curve, approximate fueling curves and optimal ignition curves.  this stuff is all linked and we are talking bout changing tables in isolation...

Physically the cam tensioners are only capable of two positions, "1" which expands the tensioner. It then presses on the chain and advances intake phase. Position "0" puts cam tensioner into default "retarded" position. AFAIK the ECU has no ability to modulate that into any intermediate phase. It is either, ON or OFF.

In the advanced "1" phase, the intake valve phase overlaps exhaust valve phase by a considerable amount.  Normally I believe it is only 2 deg as measured here http://www.audizine.com/forum/showthread.php/297064-Cam-profile-data-for-all-factory-cams (http://www.audizine.com/forum/showthread.php/297064-Cam-profile-data-for-all-factory-cams). Add 18 deg of cam advance and suddenly you're overlapping 20 deg, which essentially leaves door open for either exhaust gas to back into intake or intake to exhaust. Due to air inertia though I believe that some clear air pushes exhaust gas out with some fresh air inevitably just escaping through that path. That's the secret behind improved economy and torque on cam advance.

The result though is that engine effectively consumes more air than it is really using for combustion, which would result in AFR inbalance if not corrected via these "helper" tables.

This would also explain notch in MAF readings. Engine is using more air with NWS active than with NWS inactive and when NWS inactivates you see the drop since the venting is not taking place anymore. The engine is using less air now per piston than before.

Thanks for a good explanation julex. I'll update my tuning guide with discussion from this thread, so if I ever get Revision 2 out you might recognise some of the words.

TTQS

Here's a good quote from prj in another thread regarding this (reposting here for future reference of something to try):

I have a notch!

This is after setting KFPRG and KFPRGNW to like values. I've never gotten a notch before, so I wanted to post it :P

Will you throw in WGDC to that chart please?

Kind of irrelevant as it's a notch in requested, not actual :P

But sure. I will a little later.

I'm interested in how much change in WGDC there was during the notch is all.

0 change.

The issue was in KFPRG fwiw.

Fastes way to get rid of this boost req drop? But to keep NWS active

KFPBRK and KFPBRKNW  al to 1?

Had a notch in requested boost at 3880 rpm. That exactly solved the problem. Thank you for that!