TFSI low specified boost?

[BoostedGogre]

Hi Boys, i am fresh owner on B7 TFSI and i have boost problems, last week check car for error codes and found "P0299 - 002 - Control Range Not Reached" , N75 valve duty cycle was 0%, so i decided this valve is the problem. I bought new N75 valve and new diverter valve last revision, replace them, membrane on my old diverter valve was heavely damaged. Car working good, idle was stable, rev good, clear old errors no new one, but specified boost pressure is to low and duty cycle on N75 is 0.0%, and no boost?
Any suggestions???

720 /min Engine Speed (G28)
99.0°C Coolant Temperature (G62)
14.3 % Engine Load
2.06 g/s Mass Air Flow Sensor (G70)
2.06 g/s Mass Air Flow Sensor (G70)
6.3 % Cam. Adjustment Intake Bank 1
89.5 % Engine Load (spec. corrected)
0.0 % Boost Pressure Control (N75)
270.0 mbar Boost Pressure (specified)
890.0 mbar Boost Pressure (actual)

2880 /min Engine Speed (G28)
100.0°C Coolant Temperature (G62)
13.5 % Engine Load
7.61 g/s Mass Air Flow Sensor (G70)
7.61 g/s Mass Air Flow Sensor (G70)
39.2 % Cam. Adjustment Intake Bank 1
127.1 % Engine Load (spec. corrected)
0.0 % Boost Pressure Control (N75)
230.0 mbar Boost Pressure (specified)
920.0 mbar Boost Pressure (actual)

[EvolutionArmory]

How are you collecting that data?

Your second group says you’re only getting 7.6 Gs on the MAF at 2800 RPM unless I’m reading the info wrong. Do you even have the gas pedal floored? Are you coasting or something?

[BoostedGogre]

How are you collecting that data?

Your second group says you’re only getting 7.6 Gs on the MAF at 2800 RPM unless I’m reading the info wrong. Do you even have the gas pedal floored? Are you coasting or something?

VCDS. You are correct on MAF. Engine is reving to max rpm, my log is on 2800 but pedal is not floored, just save log on 2880 RPM. Car is parked when data is recorded.

[EvolutionArmory]

Ok. Your car is not making any boost at idle. None of ours do. The pressure you are seeing as actual is the atmosphere being registered by the sensor. And your N75 duty will be at zero because....well....you’re parked in your driveway 🤣

Do don’t do boost logging while you're at idle bud. You aren’t making any boost.

[BoostedGogre]

Ok. Your car is not making any boost at idle. None of ours do. The pressure you are seeing as actual is the atmosphere being registered by the sensor. And your N75 duty will be at zero because....well....you’re parked in your driveway 🤣

Do don’t do boost logging while you're at idle bud. You aren’t making any boost.

Yes car is parked but no boost on 3000 RPM? Same as 6000RPM? You mean with no load on engine in any RPM, ECU don't require boost on turbo?

[EvolutionArmory]

Exactly. Well, you might be able to build a PSI or 2 but the real answer is no. No boost.

It’s good that you’re exploring how to use VCDS. The bad part is your test isn’t telling you anything.

There is no such thing as low REQUESTED boost. The ECU dictates how much boost the car wants. You can have low ACTUAL for a number of reasons but not low requested. The reason why actual is higher than requested at idle is because at idle, the car doesn’t need boost but the MAP/boost pressure sensor is still registering the atmosphere, about 14.7 PSI, give or take depending on where you are located (elevation)

[BoostedGogre]

I hope you are right. Today i will make some logs on the road and see what happens.

[EvolutionArmory]

Only log acceleration in 1 gear. 2nd or 3rd from 1500-redline and it has to be with the pedal down to the floor for the entire log.

[EvolutionArmory]

And I know that I’m right. The boost sensor always measures atmospheric pressure on top of the boost you’re making. That’s why you’re seeing an actual of 890 mbar at idle. Atmospheric pressure will usually register between 900-1030 mbar depending on what elevation you’re at. The higher up from sea level you are, the lower the number will be.


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[BoostedGogre]

Exactly. Well, you might be able to build a PSI or 2 but the real answer is no. No boost.

It’s good that you’re exploring how to use VCDS. The bad part is your test isn’t telling you anything.

There is no such thing as low REQUESTED boost. The ECU dictates how much boost the car wants. You can have low ACTUAL for a number of reasons but not low requested. The reason why actual is higher than requested at idle is because at idle, the car doesn’t need boost but the MAP/boost pressure sensor is still registering the atmosphere, about 14.7 PSI, give or take depending on where you are located (elevation)

You are absolutely correct! When car is parked and no engine load ECU don't require boost on any RPM, but when car is moving everything is fine, N75 start to working and requested boost go higher than atmospheric pressure, up to 2000mbars! Actual boost are very close to required so case is closed.
Thank you very much!

[EvolutionArmory]

Yeah buddy, science is cool. You're in Vienna so you're at elevation which explains why your boost sensor is reading 890 mbar at idle. If you were at sea level it would read 1000 or more at idle. Mine reads between 1000-1030 mbar but I'm usually somewhere close to sea level. Maybe only 200 feet above at the most.

Just remember that in your case you have to subtract 980 mbar from your log to see what actual boost really is. So if you saw 2000 mbar that's really only 1020 of additional boost over atmosphere, or 14.8 psi of boost.