Boost Pressure & Air Mass: Explained

Hello,

Today, I had the opportunity to log data using VAG-COM for the first time. The actual value for the mass airflow sensor is consistently much higher than the target value, but I do have a faulty EGR valve!
My main concern is the turbocharger pressure. It consistently hovers around 1,000 mbar, and only when the engine speed exceeds approximately 1,600 RPM does it suddenly approach the target value, but it never quite reaches it. Could it be that the turbocharger is stuck and only suddenly releases at a certain engine speed, and consequently also releases exhaust gases?
Unfortunately, I won't be able to upload the log file until tomorrow, as it's still on my laptop.

Thank you in advance.

Thomas

klopfer wrote:

My main concern, however, is the boost pressure. It's always around 1,000 mbar, and only when the engine speed exceeds approximately 1,600 rpm does it suddenly approach the target value, but it doesn't actually reach it. Could it be that the turbocharger is stuck and only suddenly releases at a certain engine speed, and thus also causing exhaust issues???

Hi Thomas,

If it happens when accelerating at full throttle, that could be the cause. However, in that case, I think the turbocharger would already be damaged (perhaps due to carbonized oil in the bearings...).

Another possibility is that the pressure sensor is reacting erratically. If the sensor isn't located in the intake manifold, you might be able to check this with the engine off and VAGCOM running (ignition on) by slowly introducing pressure into the hose connecting the intake manifold to the sensor using a syringe, and observing the VAGCOM reading.

Ideally, an LDA would be best -> click on my signature "the essentials" .

Hello.
I had a similar problem with my 1.9L TDI AFN engine. I then replaced the electro-pneumatic converter, and everything was fine again.
If you think it's jammed, try removing the intake or pressure line and then carefully try to turn it by hand.
Examine the adjustment rod that connects the can to the turbocharger and move it.
Either use a diagnostic tool to perform an actuator test, or manually actuate the vacuum actuator.
And be sure to check your vacuum lines and tanks to make sure a badger hasn't decided to make a home there.
I'm looking forward to seeing your LOG.

Best regards,
Ralph

Examine the adjustment rod that connects the can to the turbocharger and move it.
Either use a diagnostic tool to perform an actuator test, or manually actuate the vacuum actuator.



better:

Basic settings on channel 011. The charging pressure valve is pulsed between 0% and 100% every 10 seconds.

'Because: in my ALH, the actuator test for the turbocharger boost control only runs after the test of the shut-off valve. Haaa haaaa, Nelson would say... because then the car stalls and won't start again until you exit the actuator test. It was another unemployed physicist at work...'

CU Gremlin.

because: in my ALH, the actuator test for the turbocharger pressure control only runs after the test of the shut-off valve. 'Haaa haaaa,' Nelson would say... because then the car stops and won't start again until you exit the actuator test. It was another unemployed physicist at work..

It's only logical that you can adjust the turbocharger only when the engine is off.
Otherwise, you'll have full boost pressure at idle, which is definitely not ideal.
You will still have a certain amount of available storage space under pressure for a while, due to the many storage devices.

Best regards,
Ralph

TDI Kraft ohne Ende wrote:

It's only logical that you can adjust the turbocharger only when the engine is off. Otherwise, you have full boost pressure at idle, which is definitely not ideal.

Hi Ralph,

Almost nothing of that is correct.

1. The VTG (variable turbine geometry) is constantly being pulled to its maximum position even at idle, but no boost pressure is being generated because there isn't enough exhaust gas flow.
If the loader is running smoothly enough, it will just go around and around, seemingly bored.

2. When traveling back and forth with the VTG (since it involves the basic settings ), the VTG zero position is alternately added, and then "on average, even less than no charging pressure" is built up.

If you don't believe it, take a look at it on the "live object" .

Hello Ulf,

You are right, but there are definitely some people who might accidentally press the accelerator pedal, and that could potentially cause problems. The diagnosis is designed to be foolproof.

Best regards,
Ralph

Hello,

I logged the data for about 10 minutes, as mentioned before, but I can't post the file. Is anyone able to do that for me, or perhaps take a look at the file and give me some feedback?

Regarding the turbocharger: Does the AEL engine actually have a turbocharger with a variable geometry turbine (VTG)?

Thomas.

Hi,

As far as I know, the AEL doesn't have a VTG (Variable Turbine Geometry) charger. It seems that the charge pressure control valve is integrated, but it's not adjustable; at least, in my AEL (4/96), I haven't been able to find any adjustment anywhere.

Regards,

Olli.

You are right, but there are definitely some people who might accidentally press the accelerator pedal, and that could potentially cause problems. The diagnosis is designed to be foolproof.


Okay, and that's why the actuator diagnostics and basic settings are interrupted when the speed increases significantly.

CU Gremlin.