Quote:
Originally Posted by rob love
There may well be many new developements that make propane more viable. Are the new systems in union with the emmisions control systems? Does the Oxygen sensor (and the host of others in the emmision system) control the fuel's injection system? Back in the day, the propane system merely replaced a carburetor, and was not tied in to the engines' computer...
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We fit two kinds of LPG system to vehicles: a)mixer, b)VSI
a) Mixer systems we simply install a mixer ring somewhere in the air intake system. It works like a carbie in that it creates a venturi and draws LPG vapor with the air on the way through. If the vehicle that this system is fitted to has an o2 sensor, we also fit a 'stepper motor' device that uses the data from the o2 sensor to vary the amount of LPG vapor delivered.
Non o2 mixer systems use about 20-25% more gas than petrol. Mixer systems with an o2 sensor are more efficient and you can expect to use 10-15% more gas than petrol.
b) VSI (Vapor Sequential Injection) systems are something else. With this system, we fit a gas injector into the inlet manifold right next to the petrol injector. This system is superior because it uses ALL of the engine management system data that the petrol system uses, eg, MAF, MAP, o2, knock, air temp, coolant temp, etc etc. Having all of this data allows the LPG ECU to trim fuel & ignition strategies to the point where power & consumption figures on LPG mirrored petrol's performance, to within 2 or 3%.
I should note that some vehicles return better figures than others, having said that I have a customer with a 1 year old Falcon XR6 (190kw?) who gets significantly BETTER economy from LPG than petrol.
Naturally, the more efficient an engine is at the start, the more efficient it will be on LPG.