An increased computing capacity of STAG controllers opens new opportunities for them, for instance an ability to integrate inside them devices that necessary for proper operation of LPG-fuelled engines.
The STAG QBOX Plus and STAG QNEXT Plus controllers are integrated with FLE – Fuel Level Emulator. This is used in cars where the fuel level in the tank is calculated based on the amount of petrol dosed by the injection system.
Please remember that in sequential gas injection systems the signal of petrol injectors is just the basic control signal that controls gas injectors after being appropriately processed. The petrol controller is working in the LPG mode as on petrol, thus controlling petrol injectors. However, it does not "recognize" that it controls gas fuel supply in fact.
The controller algorithm continuously counts the petrol dosage, thus, decreasing the petrol level. Therefore, the petrol level in the tank is seemingly decreased, although the car is fuelled with LPG.
To prevent it, petrol level emulators are used to restore real readings on the dashboard. Such emulators are used in the LPG STAG QBOX Plus and STAG QNEXT Plus LPG controllers.
They are used primarily in French cars (PSA Group) and Renault, although the phenomenon of apparent petrol level decrease is observed also in some models of Honda, Mercedes and Chevrolet cars.
The same device (FLE - Fuel Level Emulator) is used also in the STAG QMAX Plus controller designed to control LPG system in more powerful (5-, 6- and 8-cylinder) engines.
However, this does not close the list of additional devices integrated into the QMAX. Beside the fuel level emulator, also the FPE (Fuel Pressure Emulator) was used in cars where a fuel pressure sensor is installed in the fuel injection rail.
It is known that when the engine is switched to LPG, petrol supply is cut off by switching petrol injectors off. The fuel pump is working all the time, thus building up pressure in the petrol injection rail.
Such pressure rise is detected in cars fitted with a fuel pressure sensor and interpreted by the petrol controller as an error. The fuel pressure emulator emulates the correct pressure sensor signal, so no error is recorded by the petrol controller. Fuel pressure sensors may be encountered in some models of Volvo, Ford, Opel, Chevrolet and Jaguar cars.
As announced by the AC representatives, this does not close the integration of various, so far independent devices, into LPG controllers. Maybe ignition advance angle processors will become soon a part of controllers.
The integration of additional devices into LPG controllers is forced by market demand for reliable solutions easy to install and use at an affordable price. All these requirements are met by integrating new functions into controllers. It is easier to connect the controller. Emulator cable packages are included into the controller cable harness, thus it is easier to connect the emulator (no power supply and plus ignition connections are required). All of these improvements were made to simplify the installation, thus to reduce costs that to a large extent decide on the selection of autogas system brand.