Reprinted verbatim from the safety section of the Vialle LPI technical manual (edition 2013):
"Under no circumstances should the LPG system be activated if the petrol system has a leak. The LPI ECU monitors engine stability; if misfire count exceeds 5% over 1000 revolutions, the system shall force switch back to petrol and disable the LPG pump. Do not bypass this interlock."
The manual also details the crash safety protocol: Upon a deceleration pulse (airbag ECU signal) or engine stall with ignition ON, the LPG pump must stop within 500 ms. Testing this requires a specific resistor load (manual provides the circuit). lpi+vialle+technical+manual
| Error Code (Manual Ref) | Meaning | Fix (From Manual) | | :--- | :--- | :--- | | Err 12 | "Pressure build-up timeout" | Replace LPG filter (Vialle P/N 80-00-0015). Bleed air using manual priming routine. | | Err 27 | "Injector rail temp >95°C" | LPG is too hot. Check cooling loop; ensure engine coolant flows through the vaporizer (even LPI has a small heat exchanger). | | Err 44 | "CAN bus heartbeat lost" | Verify wiring between Vialle ECU and petrol ECU. Manual specifies pin 6 (CAN-H) and 14 (CAN-L) at OBD port. | | No comms | PC cannot connect | Loopback test: short pin 2 & 3 on serial cable. Timing: Manual requires 9600 baud, 8N1. |
The Vialle ECU is a "master-slave" unit. It connects to the vehicle's original petrol ECU via the OBDII port or by intercepting injector signals. Reprinted verbatim from the safety section of the
The LPI pump must maintain a net positive suction head (NPSH) > 1.2 bar. If the tank pressure falls below 3.5 bar (e.g., at -15°C ambient), the liquid flashes inside the pump. The manual states: “Cavitation is detected by a sharp drop in fuel rail pressure and high-frequency noise. Immediate switch to petrol is mandatory.”
To understand the contents of a Vialle technical manual, one must first understand the problem the company solved. "Under no circumstances should the LPG system be
Traditional LPG systems (first and second generation) used a "vaporizer." Liquid LPG was heated by engine coolant and turned into gas before entering the intake manifold. While effective, this caused two main issues:
Vialle’s LPI (Liquid Petroleum Injection) system bypassed this entirely. The technical manual outlines a system where liquid LPG is injected directly into the intake ports, just millimeters from the intake valves. Because liquid is dense, it displaces almost no air. Furthermore, as the liquid gas evaporates inside the cylinder, it absorbs heat, cooling the intake air and increasing density—a phenomenon that often allowed LPI engines to produce more power than they did on petrol.
A Vialle technical manual dedicates significant space to diagnostics. Common issues addressed include: