Problems while mapping the car - boost drop after 5500 rpm

[Jonas_R]

Ok,

This is one for the ECU mapping guys or someone with a good insight or just anybody

I was up at my local tuners, but while they where mapping the car we had some problems with the N75 valve. We were trying to boost 1.5 bar on my hybrid turbo, but between 4900-5500 rpm the boost dropped all the way down to 0.5 bar boost.

I dont have a stiffer WG spring, but can this cause that the car cant hold a higher boost value upto the redline? I have just bought a 1 bar wg spring, should this be ok for 1.7 bar boost?

We then tried using a bleeder valve instead, and that gave a nice linear curve and there were no problems with boost drop out. So does anybody have any suggestions to what can cause this problem?

The tuners did not know the V-map 3bar mapsensor that Iam using, but asfar as I know this should be a direct replacement and should not cause a problem?

Any other inputs to what can cause the problem?

Also I have bought a RS2 turbo, what boost values can I run on this?

/Jonas R.

[newsh]

I had an N75 that leaked where the tube goes into the solenoid, that caused a few problems.

[Jonas_R]

Sadly it aint leakings since it can hold 2 bar pressure, when i pressure tested the system

[Faheemo]

Jonas funny u mention the problem, I just logged on to see what i can find on the same problem !!

I was battling the entire night with this problem.
My car hits 1.9 bar boost, holds till 5500 rpm them falls to 0.6 bar or so.
Dont bother trying a stiffer wastegate spring, i doubled my springs up to give a combined 1.5 bar and even added shim but boost still drops.

wher did you install the bleeder valve ?

[Jonas_R]

Faeemo:
The bleeder valve is installed instead of the N75 valve, so the 8mm hose from the turbo goes to the input of the bleeder valve. Then the 8mm hose from the WG is connected to the output of the bleeder valve.

/Jonas R.

[kwlw]

Faeemo:
The bleeder valve is installed instead of the N75 valve, so the 8mm hose from the turbo goes to the input of the bleeder valve. Then the 8mm hose from the WG is connected to the output of the bleeder valve.
/Jonas R.

Is your turbo capable to flow such amount of air, that you are trying to get?

Sau

[Jonas_R]

Well that could be the problem, we did have to turn down the boost to 1.3-1.4 bar when we were using the bleeder valve.

But would the problem not be the same using the bleeder valve? Problem only seem to happen when using the N75 valve.

/Jonas R.

[Faheemo]

ok going to try the bleeder valve setup, something with the current setup is just not holding the boost.
Anybody else with some insight ? would like to keep the N75 if possible.

[prosty]

leaking bov or something? might be on the higher revs that the bov starts to leak.

[Jonas_R]

Dont think anything is leaking, because system was pressure tested and nothing leaked there. And it does not throw any fault codes at all. But else I can do some more pressure testing just to be sure.

/Jonas R.

[Faheemo]

Same this side, no fault codes, no leaks.
it almost seems that the ECU is intervening to limit something.

[Faheemo]

Are you using standard motronic ECU jonas ?

[Jonas_R]

Yup standard motronic with a Vmap-D 3 bar mapsensor.

[Faheemo]

This is getting ugly, problem is not sorted.
Bleed valve or tap to limit boost does not work.
Car just hits 5k to 5.5k and looses all power and boost !!
I have ruled out the wastegate , DV and boost leaks as possible problems.
I suspect this issue has something to do with airflow (MAF) or the RPM.
Can the MAF flow the qty of air at the high boost and rpm of the GT30R ?
or Could it be that the ecu is cutting timing cause of some event that it deems excessive like MAF reading or knock ? Any ideas ?

Jonas please point me to the list of modifications you have on your car.
I need to find the common denominator to get to this problem.
need to log some data with VAGCOM also.

[Billman]

Yup standard motronic with a Vmap-D 3 bar mapsensor.

this is probably the Motronic going into safe mode.