NefMoto

Hi all I was wondering if anyone could shed some light on my issue?

I have been doing some tuning work with a friend after a k04 conversion on my 99 S4 and it runs really well for a while but then starts pulling the throttle back to 49% ish occasionally. The main problem I can see on vagcom is the peak maf readings of 270g/s when it should be over 320 g/s running a 400bhp spec setup..i have just tested my 4month old maf against a brand new one with the same peak results...
My initial thoughts were a boost leak but having pressure tested fine twice and fitting new 710n divertor valves just in case it still reads the same.

Its weird how the car pulls like a 400+bhp car with such a low reading, I know the fuelling needs another tweak as the long term fuel trims are at +13 but what other mapping issue could cause a low reading?

I have been logging block 3,20,115 today on vagcom but what else should I be looking at?

Thanks guys

Depends on how the tune is set up.

Could be an underscaled MAF tune.

I am using an s4 maf so should have no scaling issue there.

One question on my mind is when logging on vag com block 3 showing ignition timing, and block 20 showing timing correction. is the timing correction value being subtracted from the value in block 3?

If so I am running hardly any timing which would explain low flow wouldn't it?

No. I doubt it.

Get a proper logger and post boost/MAF/load logs.

ditch VCDS, its worthless for debugging problems like this.

Thanks, yes vcds sample rate is really poor even on its best settings.

I will post something up ASAP

Is there a link between my low maf readings and also my low requested engine load? on the logs i've dont it shows my peak engine load at 150% ish which is the same as the remapped k03 spec when it should up up around 190 now for a stage 3 s4 right? so i'm thinking the various maps that are related to this need adjusting?
Am i right in thinking its KFMIRL, LDRXN etc am i on the right lines? its a 551c that i have

any help for the new boy would be much appreciated  ;D 

requested load is used to calculate boost/throttle plate (among other things)

boost/throttle plate result in air being injested, which the MAF reads, which generates actual load

so yes, they are related, but not in the sense that the ecu calculates one (actual) based on the other (requested).

rather, actual load is calculated from sensors.

I've looked at various maps within my tuning tonight and it looks alright for requested load etc, Now I am still getting low engine load and low maf readings for a k04'd s4 on vagcom! after testing the maf voltage we are seeing max reading of 5.14v so basically saying the airflow is there to max the sensor out but showing 250's g/s and 150% engine load.

I am using a standard s4 maf and it was accurate on k03's as far as I know so could anyone shed a bit of light on this? It's driving me mad..

I forgot to ask, what effect would it have on the ecu seeing the wrong airflow and engine load?

uh, you are in the wrong region in most of your maps?

you've maxed out your MAF.

Get a larger diameter MAF and scale MLHFM accordingly.

some underscaling is fine, but you DEFINITELY do not want to hit the 5.1V on the maf.

[nyet]oh sorry, i accidentitally edited your post instead of replying to .. sorry ... and i can't edit it back![nyet]

To answer your question about S4 maf:

No, nobody uses the s4 maf housing for k04 tunes because it maxes to 5v too soon since it is very narrow.

The s4wiki contains more information about MAF scaling, both in the tuning article, and in the MAF article.

we tried to look at maf scaling tonight and have a problem with the hex address/id. in tuner pro the maf correction table is 14f71 but in our tuning software that address is the primary fueling map.. the voltage chart for this ecu crashes tuner pro as you know, but the main issue is most of the maps defined in bin/xdf's files dont tally up with whats on my ecu.

Is it actually possible to show correct load and maf on the 551c?  i can upload my tuning file if it will help?

yes/no    i currently do but that's because i want to move to the bosch rs4 setup instead of my old hitachi 85mm setup...

The majority of euro/uk tuned s4's run k04's with the standard maf no problem but i'm not sure how many of them are 551c ecu's.
there seems to be very little development on here compared to the m-box for example and as i mentioned the xdf's dont tally up with my ecu locations although the values look right

switch to k or m-box..

there is a new k-box xdf out now (thanks to prj).

forgive my total lack of knowledge on this but how would a go about running m-box software on my c-box? can you point me to any threads please while i search for info.

Unfortunately, you'll have to find a box with a 1M flash.

C-box has the 512k flash

i will keep my eye out for one, i have two 551c's  :'(

If its just a case of vagcom showing the wrong readings for maf and load i can live with that as long as it doesnt cause conflicts within the ecu, although it will still annoy me. The car drives great at the moment and not doing anything it shouldnt but would still like to get to the bottom of it