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Hi all, im from malaysia.
I drive an Audi RS6 C6 2009 SEDAN.
Stage1 VSPERFORMANCE tune, bmc air filter and 2nd cat delete.
I have an issie with my boost cluster where its stuck at Max after wot. When that happens, theres power loss. In order for the boost cluster to work again i had to stop the car. Please help as i am clueless with this issue.
I have changed the diverter bypass valve and issue still remains.

My whatsapp +60179175735.
Your help would be very much appreciated.

This is the boost cluster i was talking about

Will only drop when car is stop.

Hi Erwan, that looks like a G71 sensor failing but I would suggest getting your car ECU fault logs read before changing anything and posting any faults back on here.

The reason I think it is the the G71 is that the G71 Intake Manifold Pressure Sender sends the combined boost level from both turbos (as felt in the manifold) to the ECU. If that stops working properly (either fails to work at all or stays high like yours) it will give the ECU incorrect information and cause problems so I'd look at that first.

There are other sensors which are used to control the Boost but these are not used for the display. These sensors are split between the two turbos so there is a boost controller, N75 for left turbo or N274 for right, and boost pressure sensor, G31 for left and G447 for right, for each turbo and all the sensors mentioned work together to control the boost like this if there is no problems -

• Both turbos spin and make "wastegate" boost levels (mechanical limit set with spring pressure).

• N75 and N274 says "I want to make more boost so I'll hold the wastegate closed to raise the boost".

• G31 and G447 measures that boost and sends it to the ECU as feedback.

• ECU looks at those two sensors readings and says "N75 and N274 you have reached the right boost level. Now hold that boost level by opening the wastegate a little bit".

• G71 then measures the total combined Boost from both turbos inside the intake manifold and sends it to the ECU.

• The ECU then uses the G71 measurement to control fuelling and timing

However, in your case it looks like the G71 sensor is telling the ECU that the turbos are always at full boost, causing the ECU to add too much fuel, which the Lamba sensors will then detect as over-fuelling (because the car is Not at full boost) and sending the car into a limp home style mode until you switch power off and reset the reading from the G71.

The G71 sensor is Item 6 on this image (middle on the far left) -



and it looks like this

What an answer, hats off to you.

Cheers

Could be completely wrong TBH, cars with so much electronics are a pain to diagnose

FrazerD wrote: ↑

Sun Nov 18, 2018 11:14 am

What an answer, hats off to you.

Cheers

+1