Intake leaks

[mbagge01]

On my 2004 cayenne turbo with evom tune, I notice that my timing is being pulled under heavy boost and car feels like it has no power but it reads proper boost. I found that the drivers side intake pipe to the turbo has some play in it, which is likely a bad o-ring which I plan on replacing. Could I be leaking air from this area, and enough for the car to be pulling timing under boost. I have already replaced all the other obvious issues like coils, spark plugs, fuel pumps, etc.

[hahnmgh63]

I would think if you had a air leak then it would have less boost and there would be no reason for the ECU to pull timing? Overboost is the usual reason for the ECU to pull timing.  The Cayenne has ME7.1.1 which happens to be the same version Motronic as your RS6. Overboost usually will throw a code and run it into safe mode but underboost due to a small leak rarely throws a code. A leak prior to the Turbos which causes un-metered air to bypass the MAF's will usually throw a lean code. Have you checked for fault codes yet?

Worst case is detonation due to overboost or impending knock will pull timing. Almost always, 99.9% of the time the knock sensors will sense the vibration of impending knock and lower boost and/or pull timing depending on the severity of the sensed Boost. The ECU and sensors are smart enough that they can pull timing by individual cylinder. How is the fuel quality your using?

Bad Knock sensor (two installed) can be a cause, air intake sensor/map sensor (located on Y-pipe), water temp sensor, to name a few culprits. And yes, you can have a bad air intake sensor or MAP sensor that reads out of range but doesn't fail enough to throw a code.

Edited November 3, 2016 by hahnmgh63

[mbagge01]

The best fuel I can get in Portland is 92octane which I use. If I am loosing just small amounts of air from that pipe that exits the turbo and connected to the intercooler, which is pressurized air, could that small amount of air lose be enough to throw off the air fuel ratio and cause timing to be pulled as this would be air lost that would be expected to be still there that was measured when it initially came into the system at the MAF. Also could it be that if it was a small leak it might not necessary cause much drop in boost pressure. I know how these cars are very sensitive to extra air or lose of air in the system, even if small when the ecu is making precise calculations for air fuel. My car does not read out any codes.

[ekstroemtj]

On 24.12.2014 at 6:44 AM, hahnmgh63 said:

I would think if you had a air leak then it would have less boost and there would be no reason for the ECU to pull timing? Overboost is the usual reason for the ECU to pull timing.  The Cayenne has ME7.1.1 which happens to be the same version Motronic as your RS6. Overboost usually will throw a code and run it into safe mode but underboost due to a small leak rarely throws a code. I leak prior to the Turbos which causes un-metered air to bypass the MAF's will usually throw a lean code. Have you checked for fault codes yet?

Worst case is detonation due to overboost or impending knock will pull timing. Almost always, 99.9% of the time the knock sensors will sense the vibration of impending knock and lower boost and/or pull timing depending on the severity of the sensed Boost. The ECU and sensors are smart enough that they can pull timing by individual cylinder. How is the fuel your using?

Bad Knock sensor (two installed) can be a cause, air intake sensor/map sensor (located on Y-pipe), water temp sensor, to name a few culprits. And yes, you can have a bad air intake sensor or MAP sensor that reads out of range but doesn't fail enough to throw a code.

 

 

Mark...

 

just read your old post.  I am hunting for my overboost reason.  You mention water temp gauge can be a culprit. I bad thermostat too?