AFN Turbocharger: 2 Bar Boost, No Limp Mode?

AFN, chip tuning, VTG17 turbocharger, normally 1.2 bar boost pressure, limp mode activated above 1.4 bar!

My wife told me today that the engine wasn't producing any power on the highway. So, on the way to the cinema, I gave it some gas, and to my shock, I saw the boost pressure gauge rise to 2 bar. I immediately took my foot off the accelerator.

Lifted the hood and roughly checked the vacuum hoses ----> OK.
Disconnected and reconnected the vacuum hose from the VTG (Variable Turbine Geometry) control unit ----> VTG control rod operating correctly.
Driven without the vacuum hose connected ----> Boost pressure increases to 0.5 bar at 4,000 RPM.

'I'm concerned that it's not going into limp mode. Could it be that the boost pressure sensor in my engine control unit is faulty? However, everything works perfectly fine when the accelerator pedal is pressed up to about 1/3 of its range!'

A faulty boost pressure control valve usually manifests as too low boost pressure, right?

Great, I have to drive 300km tomorrow. But thanks to LDA (Linear Dynamic Adjustment), I can control the boost pressure with my foot.

Regards,

Manuel.

Manuel Thomas wrote:

I'm not worried that it doesn't go into limp mode. Could it be that the boost pressure sensor in my control unit is defective? However, everything works perfectly fine with accelerator pedal positions up to 1/3! A faulty boost pressure control valve usually manifests as too low boost pressure, right?

Hi,

Regarding the LD (boost pressure) sensor: You'll be able to determine if it's defective by examining the parameter measurements (log data). This will show you the actual LD value and how much the solenoid valve is still being activated. An error may not appear immediately due to the adjustment phase, which introduces a delay. It depends on how long the boost pressure was too high and whether the engine control unit (ECU) detects it.

The actuator may also have other defects. If the valves at the outlet no longer allow significant vacuum, it is usually because the control nozzle is clogged with small foreign particles, which is the most common defect. Furthermore, the supply line for atmospheric pressure may be blocked, or the anchor of the magnetic coil may be stuck due to contamination.

With this information, you should be able to narrow down the source of the error. It's also possible that the LDA is displaying incorrect values.

Okay, the problem seems to be resolved. It appears that the VTG (variable transmission gear) was jammed in the lower position due to the short-distance operation for 7 weeks.

After 150 km, the oversteer became much less pronounced, and after 200 km on the highway, everything was back to normal.

Regards,

Manuel.