Im experiencing a wierd lean condition at WOT, after around 4500rpm the MAF reading goes down and the actual AFR leans out.

Here is a log, WOT in 3rd starts at row 480: https://docs.google.com/spreadsheet/ccc?key=0AlddzLucZT07dEU3UmYta0VKbms5TWl6b3YydFlWcUE

2002 Audi A4 1.8t, returnless:

HTA2868r Eliminator, ported
Ported BEX manifold
Ringer Racing 1000cc EV14 Single tips
S8 4.2l 3.5" MAF
Maestro 7
BSR 1.5bar Boost guage
D1 Spec catch can, -10an lines
Black anodized Evolution Racewerks Competition FMIC, custom piping 2.25"/2.5"
Custom 3" downpipe with 100cel race catalyst
Ferrita stainless resonated /w 3.5" tips
Aluminum piston type DV
ECS snub mount
Stern soft motor mounts
Stern transmission mount v2
Apikol soft rear diff mount, billet version
Clutchmasters FX400 6-puck
Clutchmasters 240mm 19lb steel flywheel

I have pressure tested the system at ~1bar, I have tried plugging all ports on the TIP(evap, ccv and plugged DV) as my first thought was air leak post-MAF pre-turbo since the boost doesnt drop, none of that helped. I had this exact symptom when I was still on stock turbo and stock MAF, rest of the setup was the same except for turbo/MAF. I was pretty sure it was my stock TIP collapsing and I never attemped to fix it since I was going to swap in my bigger turbo and MAF.

I have not verified fuel pressure yet, but to my eyes it does not look like im running out of fuel, though im not ruling it out. The fuel pump/filter is stock and was changed less than 2 years ago.

I have a feeling this could be software related, but im stuck, I cant figure out were to look.

I doubt it is the tune. If it is, you'd see it in injector duty cycle

You're running out of fuel (bad injectors, failing pump, etc)

If possbile measure block 2 for injectors duty cycle.

Wow. You're right. That is extremely odd. I don't see your MAF dropping low enough to cause that kind of injector cut.. Some thing else is going on. I've never seen that much fuel cut.

Don't forget, though, your load is supposed to taper down with rpm after peak boost (although MAF should not)

Also, please post the original CSV so I can run it through ECUxPlot...

your MAF is taking huge dive, which is causing you to go lean two ways

1) your load drops off a cliff, sending your req lamba into a low load region (lean)
2) injector drops because the MAF is dropping.

If i had to guess, i'd say its a DV problem.

DV is not leaking, pressure tested the system at 1.5bar, no leaks at all.

Did some more logging, and have found the cause:


This is my current KFKHFM:


I cant understand what is wrong?

I think you'll need somebody here to disassemble your bin to find out what else can affect fkfhm

I have noticed that this correction seems to happen when actual boost > requested boost, if anyone want to take a look I have attached two logs.

Seems strange if the ECU wants to correct boost overshoot with scaling the MAF reading down, no?