The ones I drove were conversions. That was (and is) quite normal here. Only a few years ago did the 'factory' Bi-Fuel cars become available. (strange rules in the vehicle laws meant that you could not legally sell LPG cars from the factory..)

Volvo here usually has a deal with Vialle for their LPG systems, so any installations done through the dealer are Vialle systems most of the time.

All modern systems are multi-point and support sequential injection. Most systems 'piggy-back' on the normal engine management and splice into some sensors and injector circuits.

So the normal engine management computer is still operating as it did before (inlcuding full closed-loop running with lambda control). Only difference is that it's now (through an add-on computer) triggering LPG injectors instead of petrol injectors.

This system also takes care of the initial startup, which is normally done on petrol, and then it gradually switches to LPG once it's running. Because of this the petrol injectors are used regularly, so they do not gum up.

The fuel gauge also shows either the LPG or petrol amount in the car, depending on if it's running on LPG or petrol.

Bye, Arno.