Weak AHU Performance: Troubleshooting Guide

Hello,

I have the feeling that my AHU (engine) isn't pulling as well as it used to. It's possible that I'm just imagining it and everything is fine. I did a logging session and would like to ask you to take a look at the data. What I noticed from the log is that the manifold absolute pressure (MAP) starts to drop around 3600-3700 RPM, and it's entering the soot limit. The engine has been tuned to approximately 110 horsepower by Rainer.

Here are the logs.

Hi,

Standard deviation of the air mass sensor?

Best regards, Rainer.

For me, it looks more like a "weak turbo."

While the LMM (likely referring to a lambda sensor or air mass meter) might show a slight decrease in performance at high RPM, it's not significant enough to cause the engine to shut down or reach its limits.

It only improves my initial acceleration because the turbocharger isn't building boost properly. And with the AHU system, it might be due to the wastegate turbocharger, which isn't a variable geometry turbocharger and therefore doesn't respond as well at lower RPMs.

m;

Hi,

Quote:

The LMM (lambda measuring module) may give in at high speeds, but not to the extent that it would cause the Russian border to close.

Yes, but it's questionable whether the approximately 2% power loss at 4000 rpm is really noticeable...

Best regards, Rainer.

To me, it looks more like a 'weak turbo'.

Me too.
because the target load (LD_Soll) is not reached until 2200 rpm.

Please check the vacuum supply to the pressure sensor and the N75 valve.
There might be something wrong here, which is preventing the bypass from closing properly.

Best regards, Jochen.

@ Jochen:
OVERPRESSURE... it's a waste!

@ Rainer:
I only argued based on the graphics. Yes, there's a minimal "clicking" sound, but then it continues beyond the rotational speed limit.

m;

Okay, then it's probably just my imagination. I just wanted to make sure nothing is broken. I had a car accident, and oil spilled onto the mass airflow sensor (MAF). It might also be due to the spark plugs, which have 180,000 km on them.

But thank you for your help.