NefMoto

I'm tuning Golf IV VR6 Turbo. Siemens 630cc injectors, stock 3'' MAF, t3/t4 turbo.

Moded maps:
KRKTE
A little richer than original in highest loads tuned in ECM software
KFMLDMX (I had "MAF signal is too high" DTC)

I have a problem. When i was running at dyno the load at 4000rpm is about 130% and I have about 0,7bar boost, hold about 11 - 11,5 AFR. At about 4200rpm the load suddenly decrease to 90% and AFR rising to 15-16 and engine sputter. I don't have any DTC but general lambda is switched off in that moment (come down to "0" value on VCDS). What could be wrong?

Best regards

no clue. Log.

throttle cut?

Tommorow I will post logs. I think this is not throttle cut because engine want to go up. But it's like load cut caused by moving to another map in ECU because afr suddenly escalate to 15-16 in that moment. I don't know why this happens...

Have you 100% eliminated hardware as a potential cause for your cuts? Like a dead fuel pump?

I'm posting logs. Is it possible that stock 3'' maf is too small to this setup and this is the cause of cuts? Other hardware potential causes are not.

from what i see in your logs, it seems like the maf is hitting over 300g's which is like 4.7 volts? which is probably around maf limit, you sure thats 3 inch?

turn the boost down a little and see if your problem goes away, i have a feeling it will

Are you sure your fuel pressure is remaining constant throughout a pull?

The problem was genuinely with MAF. This was stock VR6 maf and it have 4.7V at about 5000rpm. I changed to S4 B6 3,5 inch and now it's perfect. :)
Thanks :)

What did you do about mlhfm?

I was surprised by this, but I didn't do anything with it. It works fine on stock mlhfm.

I'm building a vrt as we speak. I thought with that setup you would want the 4 inch maf?

Did you use the stock sensor?

It's underscaled if he's using stock MAF table.

Yes, this is stock sensor

Now I have another problem with that Golf. I don't touch the ignition maybe I done this a little and it always and still retard the ignition by knock sensor on knock corrections. On max load it can retard about 10 degrees. I have external knock sensor and I don't hear a knock. It does not help also if I put 100oct. V-Power fuel. I don't know what it could be... There was only done KRKTE, MLHFM is pull down and fueling map in ECM. Golf has 1,2 bar boost and have about 300hp now, but it should be about 310hp on 0,7 bar.

On pump you wont see more than 5*BTDC max depending on how much boost you are running and what RPM's tbh