Prins AFC Compact / VSI-2 calibration – MG ZS 1.5 DVVT-i (P0420 issue on LPG)

Hi everyone,
I’m looking for technical support regarding the calibration of a Prins AFC Compact / VSI-2 system installed on a MG ZS 1.5 DVVT-i (engine code 15S4C, 2022, 106 hp, naturally aspirated).

Since the installation, the car runs well on LPG under load, fuel trims look acceptable, and gas pressure is stable.
However, I constantly get a P0420 “Catalyst efficiency below threshold” fault when running on LPG.
With petrol driving the alarm goes back.

On petrol, the downstream O₂ sensor is stable around 0.6–0.7 V (no oscillation).

On LPG the downstream O₂ drops to 0.1 V and stays low for a long time, which triggers the P0420.
Do you have a basic setup (calibration) to start setting the parameters with? Do you have a guide? Thanks.

 

Ciao,
i share you the log file (test driver petrol and lpg) and the configuration parameters.

• Car Type: MG ZS 1.5cc 106hp natural charge 2022
• Engine: 15S4C DVVT-i
• LPG injector type: KN-9 63cc (orange)
• Nozzle (jet) size: 63cc (orange)
• Gas changeover temperature: 40c
• Engine power on LPG compared to petrol: you can check in the attached file
• Upstream lambda value / voltage in LPG operation: you can check in the attached file
• Short-term and long-term fuel trims on petrol vs. LPG: you can check in the attached file
• pressure reducer type: eVP-500

You can see parameters in the file "prins_IDs_report_modified".
i set also the MAP and the gas pressure is variable. i put the picture in the file.

Thank for your support, I really need support.