i have a vs 5L in my hz ute and im getting it converted to lpg. now im told by the gas bloke that i can not convert it to straight lpg as the eng needs fuel to start. this seems strange? i would have though it would be possible. i want to get rid of the petrol tank and fuel filler and also not run any cats. so straight gas would be the go! any ideas?
It depends on the particular gas set up. One issue is that the vapour hose takes time to fill if the convertor is mounted some distance from the gas carb. This will result in an extended crank time as the air is replaced with LP vapour, but can be fixed by including a vapour lock off solenoid in the vapour hose at the carb, trapping the volume of gas in the hose. Starting on petrol avoids this. There may be some issues with poor LPG vaporisation with very low temperatures but it's not a problem with temps above zero (or not much below). You don't give a location but in Aust. you will still have to run a cat and closed loop fuel control on straight gas as the engine must comply with current regs. The original HZ engine, being pre ULP/cats, converted to EFI would not.
I believed the cat was not necessary on gas only cars due to the very low emission levels, I may be wrong. The builders of kit cars eg AC Cobra Replicas have always run straight gas to avoid having to fit a cat and other pollution gear plus the benefit of more power on gas than petrol.
Search 'AS1425'. It used to be the case that a formal emissions test was not required on LPG conversions. For conversions post Jan 2004 on vehicles meeting ADR 79/00 (Euro III?) on, LPG conversions must be submitted for type approval testing ie. a full 'shed' test for an example of the conversion as it will be installed.
ah ok cheers for the info! the lock off valve ill mention to the gas installer. he told me there is no way of doing it! the eng is vs with vn computer and chiped to around the 190. also its chiped to suit straight gas so it will be good to get it on as it runs a bit roungh at the moment being on fuel. =). i didnt use the old red block and bolt on the efi gear as it was just heaps easier to use the complete eng and not worry about it. cheers! jason
