NefMoto

Greetings,

I have been tuning my S3 1.8T for a while now (roughly 2 years), and converted it from the standard K04-023 to BT.  The specs of the build are as follows:

S3 BAM

8N0906018BJ
0261207752
363001

RC 750 cc injectors at 3 bar
Walbro pump in-tank (issues at 1/4 tank but that's not the problem here)
Larger FMIC (Dual SMICs ditched)
MBC (N75 is currently broken, will be purchasing a new one shortly, I know MBC is trash).  The motor is still stock, internal wise, so the delayed spool is kind of a good thing at the moment.
Mostly Not Working WMI (ancient pump)

I had no issues dialing in the RCs, KRKTE, TVUB, KVB, FKKS, TEMIN/VA and KFMRES/KFMRESK and a few other maps helped those to be dialed in nicely.  I have scaled KFMIRL and KFMIOP correctly, with the 99% column at roughly 225 load, and the KFMIOP axis extended to 225, and interpolated correctly (Using PRJs sheet).  The MAF is underscaled with KFKHFM, and fuelling overscaled with FKKVS in the boost area.  I know that this isn't the best way of doing it, but it has worked well to 2 bar plus on a Mk4 GTI that I helped tune).  The underscale is relatively minor in this case at 10% .  I am running 1.5 - 1.55 bar, but even when I turn it down to 0.9 bar, the ECU will cut boost around 6500 rpm regardless of actual load or boost. 

It's really frustrating.  I will attach logs of both cases and in both cases the requested boost / timing drop off sharply, when boost doesn't follow requested (MBC) it will react with throttle cut.

It really seems like a type of torque intervention, and is really frustrating as I intend on forging the motor and running Ethanol and over 2 bar (30 psi) boost.  I have tuned a Mk4 GTI Big turbo to over 2 bar and it never had this reaction.

LDRXN (215)
LDRXNZK (LDRXN - 15%)
KFMIRL (Raised - but same issue with stock)
KFMIOP (Raised - but same issue with stock)
KFDLULS raised
KFMLDMX raised
KFLDHBN raised
ARMD adjusted
LDRXN requesting 215 under boost (reasonable for BT out of boost)
CWBGMSZS set to 0
FWFTBTRA adjusted
EGT maps raised slightly (EGT is in the DP so this is not really an issue)
VVT maps adjusted to turn off earlier under high load
TLDOBAN adjusted
KFWZ/2 adjusted
KFZWOP/2 adjusted (for new axis)
NMAX (7100)
NMAXOG (7100)
KFSZT/FTOMN/KFTSRL for HC Limiter

All then normal maps (KFZW/LAMFA/LAMFAWKR/KFLDBTS etc have been tuned for a reasonable fuelling request under boost, and it's fairly good).  I've also tweaked a number of other smaller maps for fine tuning various parts but nothing that should cause this issue.

I have tried maxing out KFMIZUFIL and KFMIZUOF (6000+ but to no effect) It looks like Level 2 torque intervention in anycase.  I've spent hours reading through nefmoto threads to try get an idea of why rlsol_w is taking such a massive dive after 6250-6500, as it's so boost/actual load/knock/fuelling/MAF independent. Is it perhaps an issue with this binary or the S3 load-path vs other 1.8Ts?

Any help would be greatly appreciated.

Regards,

Jono

With both Stock MIRL/MIOP and edited MIRL/MIOP I had LDRXN around the 210/215 load request level, is this perhaps too high?

Is it possible that the other rpm limiters are coming into play? I.e
- NMAXDVG
- NMAXGA
- NMAXDV
- CWNMAXMD/CWDNMAX

Which are currently all stock.

I am also logging my car with the cluster fuse out, I tried the SLOW code edits but they didn't seem to allow me to connect using Me7L with the cluster fuse in unfortunately.
Perhaps gear dependent limiters like:

- KFMDBGRG ( - > MDKOL -> MDFUE) etc
- MDBGRGA

Do not max out req boost. I do not know how many times I've said it, and there are copious warnings about it in the S4wiki tuning page.

Even with the load axis scaled to above LDRXN?  So then, keeping MIRL/MIOP stock and reducing LDRXN to 190 should solve the issue then?  I've seen some other tuned files and logs for this particular binary where MIRL/MIOP had been scaled to 240/250, and LDRXN was set at something insane like 1556 (maxed to the bit limit of LDRXN), and it didn't have this issue.  Granted there were tons of other edits, so perhaps all kinds of torque interventions were disabled.

Looks like RPM limiter to me, and keep in mind the valves will float at ~7300 rpm on stock valvetrain, so don't go nuts on it.
What you're doing with your boost request is pretty stupid though. You should not ask for more than 2450mbar ever without 5120 file. Although if you have a MBC (which is another stupid thing to do), then it doesn't matter too much.
What worries me more is that you have scaled stuff so much that req load is around 200, while actual load with boost on target is at 175. That means if something happens with boost control you are likely to blow the engine up, because it won't limit anything until around 2 bar.
Another thing is, that the rods on this engine are made of paper and you will bend them eventually at 1.5bar boost (BTDT).

I can sell you 5120 for this platform if you want it ... but it seems there are other things to take care of first.

This entire post ignores why maxing req boost is a bad idea.

I do understand, as DSLOFS is still stock, so the requested value is higher than the possible sensor value, which upsets the boost PID.  Where it cuts boost, the requested has dropped below the max though.  But the point has definitely been taken and I will revert MIRL/MIOP to stock and drop LDRXN as well so that it stays on or just below 2450 mbar request.

Thanks, I will attempt to raise the other limiters which are currently still stock, namely:

- NMAXDVG
- NMAXGA
- NMAXDV

It's just odd that the limiter is so proactive and starts to drop load so early.  Also yes I am aiming for a maximum rpm of around 7000, no intention to go higher just yet until after the forged build with upgraded springs/valves/retainers etc.  I was aiming for around 1.3 bar, the 1.5 bar was during logging while adjusting boost using the N75, after a revision or 2 it became clear that the N75 solenoid was faulty and not directing boost pressure to the wastegate, so 2500 mbar was essentially the maximum.

I appreciate that, closed loop control would be perfect, but as you said, the stock motor won't last all that long on stock rods at near-to-above map limit pressures.

On further reading I suspect the issue is NMAXDV, as I am logging with the cluster fuse removed to get ME7L to work, and I have not raised NMAXDV from its stock value.  Removing the cluster fuse (as most know) divorces the ECU from the cluster and by association the VSS (Vehicle Speed Signal).

Did this fix your issue? Ive been fighting this problem for over a year. Happens reliably at 6000rpm in 1st gear, in the past it wouldnt happen in higher gears than first. My requested boost dive bombs at 6000rpm then 1ms after that the throttle cuts to like 45%. Not over-boosting at all when it happens. Started from scratch like 10 times and have spent like 100 hours trying to figure out what it could possibly be. My nmaxdv maps were at 6800rpm in this run but i usually set it at 7000. Should i set it even higher than my actual rev limit since it seems to be pre-clenching in preparation for 800rpms before the limit?

Ive even tried using an 018ch ecu and tuning that and get the same result. Starting to think its my car thats causing it (b6 a4 1.8t gt30)

Cant do much w/o an actual log

raised the rpm limits and no change. Do i need to log anything specific that im not already to figure it?

log the rest of the load vars.

Can't diagnose requested load if you don't actually log the whole path.