S3 overboost problems

[Slicker]

Hello,
i have overboosting problems with my s3. It is 210HP engine, year 2000.
This is fault code:17963 - Charge Pressure: Maximum Limit Exceeded
P1555 - 35-10 - - - Intermittent

Car isnt chiped yet, but it has FMIC, 007p DV, deleted N249, bigger intake manifold and milltek catback (decat with 2.75" downpipe). All hoses seems to be OK, i replaced LMM (maf sensor) and n75 with new OEM. I have boost gauge and it is boosting over 1.3bar, car goes into limp mode only in 5. gear at around 5200rpm. Did anyone had the same problem on standard map? I have also disconected n75, it's the same, only difference is that it goes to limp mode in 3. and 4. gear also . Boost is the same. Turbocharger has been renewed 10.000km ago, but i assume that actuator isn't properly configured or it is broken. i will be fully grateful for your help.

 

[Dani_B19]

Mines alightly more modifiedthan yours mate and running standrad map and mine boost to 16psi but never hits limp mode or throws a code up, mine is a APY engine though and does have less sensors than the amk/bam engines.

 

[<tuffty/>]

1.3bar is too much for a std map and is why you are getting that code... assuming you have the N75 plumbed in correctly I would try electrically unplugging the N75 and see what boost you get then... actuator pressure is 0.5bar... if you are getting more than this then it suggests a potential issue with the actuator...

Double check you have the N75 plumbed in correctly... as a further test try taking a pipe directly from the outlet on the charge pipe for the N75 to the actuator... this should narrow the issue down a bit...

If you are still getting high boost then it could be too much preload on the actuator, broken actuator, sticking wastegate etc... what turbo went back on? genuine std K04?

<tuffty/>

 

[Slicker]

turbo is standard k04. i have already unpluged connector from n75 and problem stays as i wrote above. i dont exactly understand what do you mean with rewiring n75 and actuator. i assume that n75 is pluged correctly. where can i get any scheme to be sure?

 

[<tuffty/>]

Using this pic of an N75...

The longer outlet goes to the TIP, the opposite outlet goes to the actuator and the one in the bottom is where the boost goes...

After a re-read of your spec its plausible that with the larger inlet and FMIC that there is a lot more flow than the std map can handle... if this is the case then arguably the only thing you can do to prevent further problems is to fit an MBC such as the Forge UNOs in parallel to cap the boost spike or get the car properly mapped...

I would also check the actuator preload in case this is too much... you can also try the test I mentioned before by connecting a pipe directly to the actuator from the charge pipe outlet for the N75... this eliminates the N75 as an issue....

If you are getting more than 0.5bar on a std K04 then it suggests there is something wrong with the actuator and/or wastegate... this could be a preload issue, faulty actuator (assuming std and not a replacement one like a Forge actuator) or it could be a fault with the wastegate sticking...

What boost pressure did you see when you disconnected the N75?

Is the turbo a genuine Audi one or one from eBay or something?

<tuffty/>

 

[Slicker]

we wanted to do a proper map, but we cant because boost goes ok to 2500rpm, then a huge hole and at 5100rpm again kicks in. turbo is oem audi. when i disconect n75 still has 1.3bar boost @ 5000rpm. tommorow i will inspect al the pipes again and n75 install. if everything is ok, think that something is wrong with turbo.

 

[<tuffty/>]

The 'hole' is due to the ECU pulling back boost because of the overboost deviation...

Like I said mate... get a bit of 6mm ID silicon tube and run it from the charge pipe to the actuator and see if it still over boosts... then check the actuator moves by applying an air line (no more than 15psi realistically)... check the preload of the actuator (I am assuming you didn't adjust the actuator at all when fitting the new turbo?)... normal preload should be finger tight with the wastegate held shut then 2 to 3 turns to tighten/add preload...

<tuffty/>

 

[Slicker]

thank you mate for you help. i will try your tips tommorow and report what i discovered.

 

[<tuffty/>]

thank you mate for you help. i will try your tips tommorow and report what i discovered.

No probs dude... hope you get to the bottom of it....

<tuffty/>

 

[Slicker]

i still have problems with overboost. i've changed exhaust manifold, which was cracked, new TIP, whick was ripper at the turbo, new n75 and i have still overboost. i am 99% sure that it is problem with the actuator. does anyone has any guide how to properly adjust it?