Hi,
I am the owner of an Audi A6 2.5 TDi avant, engine code AAT, which have PP764 nozzles and the stock turbo K14.
After several tunes here and there, I came up with a pleasant file.
The PP764 had to be a little tamed down because they´re powerful and K14 is wastegated , so it takes a little more to spool up (don´t like too much smoke).

However, despite the requested boost is 2183mbar (about 1,2bar), I never never had stable boost. It peaks at about 1,3@2500rpm and then slowly goes down to 1 bar@4000rpm. This is annoying. Looks like something is taking the boost back.

Question : if there was a SVBL (some say it is 8-bot around 2100mbar, some say it is in 16-bit hilo 1990), my requested boost could not be bigger than SVBL, right? If vag-com tells me requested = 2183mbar, then, SVBL is higher or it doesn´t exist.
I have no idea where SVBL is...

I have enough exhaust energy to spool 1,2 bar for sure. Req boost map hits 1,2 bar and boost limit map is maxed to 8-bit "255" which should be +/- 1,6bar.

Has anyone ever had this problem ? I know K14 is an old turbo, but there are Audi A6 owners (AEL or AAT) that don´t have this problem.

I have one old log i´ve made that shows the problem. Despite I´ve changed nozzles (old ones were leaking), it still doesn´t hold boost.

Hope someone can help me.

Now this will sound funny but I want to share it will others.
I had same problem with one case and it was driving me crazy.

Had 1.5boost setup from 2000-3500rpm but boost dropped at 3000 and at 3500was only 1.2. at 4000rpm only 1bar...

I taught it is a leak so i pumped complete system to check out where is the leak. I have pumped it up to 2bar! No leak...
Than i started thinking what the hell can be wrong.

By the coincidence i replaced old clutch and here was the solution :)
clutch was slipping very very little and that can be seen at boost drop if there is no leak or turbo regulation problem.
The tune was extreme,

So very funny but quite logic when you think further.

cheers

Very funny and actually it came to my mind as it happened with my ex-Audi A4 AFN while at torque peak, because the clutch was old and already shaking at traffic or slipping if torque was high. I solved it by controlling torque delivery very smoothly.

In this case, the A6 must have a good clutch (less worn), because just for fun I did an hardcore tune with my current PP764 and If I did WOT in 3rd gear at 2000rpm or so, after turbo was full, the torque delivery was brutal but it never slipped a little bit ! Only felt a litte shake in steering wheel from mass flywheel abuse...

Currently it is way softer, for economy purposes.

So, it doesn´t feel to be slipping at all during torque peak, and wouldn´t be likely to do so after that. :crazy:

I am thinking :

-Maybe SVBL ? but where is it?
-Maybe N75 map? but where is it?
-Maybe turbo is mechanically tuned to 1 bar at wastegate spring.
-Maybe wastegate is corroded - not closing properly - and therefore lets gases bypass when they shouldn´t.

..out of ideas, really. :roll: Been around this for 2 years already.

Btw... the cluth must not be slipping, because RPM don´t go up at torque peak without increasing speed. It seems solid, really :cry:

Tested again yesterday..blarg.. same problem :roll:

With more or less fuel... the effect is the same. Obviously, with more fuel, the boost drop is slower, but that because exhaust gases are working harder on turbo.

Does anyone have a clue where is N75 and SVBL in this turbo+timing eprom ? :think:

I was wondering...
When I had A4 AFN 110hp, I didn´t change the N75 map o get desired "stable" boost.

Maybe I need to change this map in my A6 2.5 TDi ? But, where is it ?

If the turbo is mechanically wastegated i think you will not find map to adjust, just a single when it will detect overboost problem and enter limp mode.

I bet you better will need to go and adjust the wastegate rod to hold some more presure before open and release.

Nice day
cml

I understand your suggestion and I´ve thougt about doing it already. But I haven´t done that yet...

I have N75 valve ! This is the only reason I haven´t adjust wastegate yet. And some AEL owners (same car with 140hp) have desired boost just by adjusting turbo maps in ECU. Why doesn´t it happen with me too ?

Maybe adjusting N75 map will do it ? But I don´t know where is n75 map. I have attached the original turbo file.

cml wrote:If the turbo is mechanically wastegated i think you will not find map to adjust, just a single when it will detect overboost problem and enter limp mode.

I bet you better will need to go and adjust the wastegate rod to hold some more presure before open and release.

Nice day
cml

Guys... anyone know where is N75 and SVBL ?

I have turbo file attached. :roll: Please...

Hi,

What map is this ? N75 ? It is 8x13 and is located at address 0779B in "turbo" file I have posted in the beguinning of this thread.

It looks like N75...