Master Questions: Expert Insights & Answers

Hello fellow mechanics!

Currently, I'm at school, and I have a professor who is very knowledgeable about diesel engines. He constantly challenges us with difficult questions on the subject.

What indicator values can indicate a faulty charging system as a result of a clogged catalytic converter?

'Refers to the EDC system from Volkswagen Audi.'

Or.
Why are pressure sensors also important in turbocharged engines that use a mass airflow sensor?

'Does anyone have an answer to this? I would be very grateful.'
P.S. I have more of them.

Hi,

Why don't you include your questions in the quiz?
/quiz.php?mode=suggest

The KAT (catalytic converter) must affect the duty cycle of the solenoid valve used for controlling the boost pressure.
When the catalytic converter is clogged, the VTG (Variable Turbine Geometry) needs to be adjusted to a 'stricter' setting in order to achieve the same boost pressure.
Due to the reduced pressure difference before and after the turbine wheel of the turbocharger, less drive energy is ultimately available.

Boost pressure sensor:
[Speculation] Safety feature for the turbocharger, as a faulty high-pressure fuel module (HFM) could cause the turbocharger to overspin. Protection against excessively high peak pressures in the cylinders (due to excessive boost pressure).[/speculation]

Best regards, Rainer.

What is correct now?

The first answer is correct. I haven't found an answer to the second one yet, I'm still looking. If you find something, please let me know.
Unfortunately, I can't add the questions to the quiz because I don't know the answers myself, and the teacher isn't providing them; we're supposed to figure them out on our own.
If anyone else wants to join in the puzzle-solving, please let me know, as I have many more.

Hello Rainer:

I think your approach regarding the safety feature for the loader is correct.
However, the boost pressure sensor doesn't only trigger when the mass airflow sensor (MAF) is defective, but also, for example, during journeys at high altitudes with low air pressure. In such cases, the engine control unit (ECU) only allows a certain pressure difference to be reached, because otherwise the turbocharger would also over-rev. Logically, the measured air mass at the same turbocharger speed decreases due to the reduced air density.

Furthermore, I believe that the boost pressure control loop is an important control variable in engine management. The measured mass airflow, as determined by the mass airflow sensor (MAF), is primarily used for the correct dosing of the exhaust gas recirculation (EGR) mixture as part of the EGR control loop.
The quantity reduction only kicks in when the soot limit is exceeded; otherwise, in my opinion, the boost pressure control system is largely self-sufficient.
I could even imagine (though this is just speculation) that the actual intake manifold pressure is needed to calculate the control value for opening the EGR valve, because otherwise there could be a short circuit from the pressure side to the exhaust.

Regards,
Alex.