Hi Tony it was based on profit as butane is lower down the refining process than propane. The higher octane lpg ron was 110 when it was mostly propane it has not been on sale for about 10 years . The main reason for lower performance on lpg is it has a lower calorific value as in it does not have the same bang per gram as pertrol so more is used for same energy output. You used to get around that by lifting compression to use higher octane rating but no longer possible ask engine builders about unhappy streetmachine owners wanting money back on dead high comp lpg motors .
Thanks for that explanation, Its nice to hear from someone with factual reasons that support my decision to walk away from LPG.
I have used it for years on a variety of cars and trucks (And even a ride on mower) and Ive always kept good fuel consumption and mileage records on all my cars regardless of what it ran on and LPG started to run close to fuel prices 4 or 5 years ago when I still had access to the suburban discounting cycles.
I noticed the LPG quality fluctuations when I was running an old 1973 International Acco with a 345 Cu Inch petrol engine, the old girl had 2 x 220 lt (180 lt usable) and id fill her 2 or 3 times a week depending on where she was filled.
I started filling at a Taxi depot Id worked at and suddenly it was mileage perfect for fill's at 3 tank fill's per week which was half what I was using.
Even at 29.9 cents per lt it was nearly $150.00 cheaper using the taxi gas on an old lpg system.
I don't have reliable consumption figures for an M117 4.5lt on LPG but my trip from Horsham in light traffic in my Brown 450SE called for 4 stops to fill the tank with LPG and I know id have done the same trip in less than a tank of Pulp.
I have seen and used Gas Research systems on a Val I used as a daily for 18 months and their throttle body system was far better than the dual fuel system that came off the car even though id spent money prior to the new system with Scorcher getting my Dizzy remapped and the car dyno tuned, ran 8mm leads, NGK Gas plugs as recommended and a whopping Echlin coil with after market electronic (CDI) ignition.
2 years ago I removed the system and sold the lot (Falcon scuba LPG tanks retained) and dropped a 4 bbl carb with Bosch pump and reg on the engine and went back to running a breaker point distributor on the 4 litre 6 cylinder engine with better economy results even running BP Ultimate ULP @ $1.55 per litre compared to 0.69 cents per litre for LPG also sourced at BP.
More grist for the mill I guess.
