boost issue B6 1.8T

Alba

Newbie
Points
21
From
Australia
Car
Audi A4 B6 1.8T
Hi guys, ive introduced myself in the newbie section. I own a B6 A4, and have remapped it with Custom code. I have taken on Superchips|Bluefin as part of my business. Anyway the dram i have is intermittently the ecu turns the boost right down. Ive logged it doing so, duty cycle of the N75 turns down and the requested and actual boost reading go to almost standard. MAF reads low at the same time. Ive tried MAFs, fixed a Lambda issue, and changed all vac pipes.Anyone experienced this one????? Something is telling the Ecu to turn it all down. As a tech ive been right through the system and seems im now missing something
Cheers in advance
Alba
 

pgarner

TC ModFather
Moderator
Points
417
From
Lockerbie, SW Scotland
Car
Octy smoke machine
i take it you have changed the diverter valve ? if it is split then the boost will be leaking.

what were the requested boost against actual boost ? if the actual goes over by 300mbar then it will go into limp mode 5psi
 

Alba

Newbie
Points
21
From
Australia
Car
Audi A4 B6 1.8T
Hey i see you are from Lockerbie, im an Ayrshire lad, been over here for 10 yrs now. Anyway mate i put a brand new DV on there from a new 9N Gti. Still the same. I is dropping to around 5psi i would say,its well below std. When on song its great. When good its 2010 Mbar and crap its around 1000mbar ish. Now i havent noticed a 300 mbar difference between req and actual, so you reckon its either a spike or a leak. Very subtle spike if it is though. Only thing i havent tried is a N75.
Cheers
Alba
 

pgarner

TC ModFather
Moderator
Points
417
From
Lockerbie, SW Scotland
Car
Octy smoke machine
Nice change for you then

its definetly going into limp mode which is normally overboost.

think i stole this off VWaudi forum a couple of years ago

Limp Mode – These cars are designed to protect themselves from engine damage. If the engine boosts too much, or the engine does not get enough fuel it will go into a limp mode where boost is limited to protect the engine. It limits boost by controlling a solenoid on the wastegate line (N75), by closing the electronic throttle or by opening the DV valve. If you are experiencing a limp mode the best thing to do is get the car scanned for codes and to see what is wrong. Look at fuel trims for signs of running lean, and to look for MAF problems, or O2 sensor problems. To look for potential boost problems log Block 115 and you can see the specified Vs actual boost. If you exceed the specified then there is a good chance that you will go into this limp mode. Stock specified is a max of 14 psi for a 2002+ car.
as your doing diagnostics im guessing you have vcds (vagcom)
 

Alba

Newbie
Points
21
From
Australia
Car
Audi A4 B6 1.8T
Yeah mate i use VCDS and have a Launch Diagun palm pilot for all the other makes. Im thinking i might undo the custom code flash. I now do Superchips. I would be worth having a stab at another flash. i must check the long term trim then. It is so on and off now its hard to catch it with logs. still its the only way really. with superchips they err on the richer side for safety. I thought lean a while back actually, its catching it misbehaving on the laptop thats the killer.
Ill see how i go
Cheers, been a great help
Alba
 

pgarner

TC ModFather
Moderator
Points
417
From
Lockerbie, SW Scotland
Car
Octy smoke machine
just a quick thought maybe not over boost but loss of boost. on top of the engine there is the notiorious Y connector that is very prone to spliting
 
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