1. Power—The LPG-Liquid-Inject System shows an increase, typically 10%, over that obtainable from the same engine using petrol as a fuel. The balance in favour of LPG can be increased by increasing the compression ratio (say 13:1 maximum), or adding boost pressure (turbocharger / supercharger) to optimise the higher octane rating (RON) of LPG. Vaporiser systems are normally 15% down on power versus petrol.
2. Torque—Figures are some 10% above the equivalent using petrol, particularly in the important low revolutions range, largely due to the volumetric effect of the phase change from liquid to gaseous (ratio 1: 243) LPG as the liquid is squirted onto the inlet valve. This very important physical principle is denied to the gaseous systems. Acts as an intercooler for turbo systems, now becoming common, or superchargers. Gas systems displace a large volume of incoming air and rarely mix well.
3. Fuel Economy—Liquid Injection is far superior to vaporiser or gas injection systems. The liquid injection kit is from 5% to 20% better. Distance travelled on LPG per litre of fuel, can equal petrol systems. A thermal efficiency figure of 40.23% has been achieved, equalling petrol. The multi-point injection system, injecting liquid LPG gives excellent fuel distribution. Again, the volumetric effect assists. The problem of moving the vapour mass (gas systems) is almost eliminated by liquid injection, as in multi-point petrol injection.
4. Variations in LPG composition—These do not worry Liquid Injection as LPG vapour pressure and temperature are read to give fuel composition. The injector pulse is altered to give the required energy input. Vapour systems cannot do this and suffer the consequences of variation.
5. Driveability of the Liquid Injection system is an excellent feature. Embarrassing backfires as on gaseous systems are eliminated. The risk of engine damage caused by premature explosion as in blowing off the engine air box is eliminated. Multi-point, liquid LPG injection sharply reduces accelerator lag. Spark timing can be adjusted to give optimum performance with Liquid Injection.
6. No petrol needed—Liquid Injection is almost the only LPG fuel system which can run permanently as a mono LPG system. Does not need to start or stop on petrol, or need petrol to offset higher combustion temperatures. The petrol tank can be removed and the space utilized.
7. Patent protection—Liquid Injection is patented and copyright is held. It will be possible to institute a constant high standard, world wide, in which motorists can have confidence.
8. Competitive Pricing—Liquid Injection kits are capable of being produced at price levels that are very competitive with the best of the vaporiser systems, or gas injection systems.
9. Plentiful supplies of relatively cheap LPG—There is adequate LPG to supply at least 20,000,000 vehicles and a maximum of 10,000,000 are currently fuelled by LPG. The world usage is growing quickly, as the environmental benefits are realised and the LPG fuel systems, such as Liquid Injection, move away from the carburettor days to multi-point injection.
10. Cost effective Infrastructure—To retail LPG is cheaper and easier to install than for instance compressed natural gas (CNG). Tanks are lighter and less bulky for the same range. The cost of compressing natural gas is high. Irritating impurities are often present in natural gas and are hard to counter. LPG is the most convenient, economic and cleanest (lowest emissions) fuel.
11. No freeze ups, easy, clean starting—The LPG is kept in the liquid state and injected in the multi-point petrol fashion, hence engine starting at low temperatures is assisted (to around minus 40 degrees Celsius). There is no vaporiser to freeze the moisture present and hence the system. The benefits of the freezing effect in the phase change are utilised to achieve a more dense air charge and hence, greater efficiency as in 2. Torque, above.
12. Sticky Injectors—As occur in the case of the petrol injectors which are idle for most of the time when gas is being used in vaporiser or gas injection systems, are not a problem with Liquid Injection. The same injectors are used to inject petrol or liquid LPG, the injector pulse being varied to give the correct energy density with the fuel being used. As the injectors are always busy they do not have a tendency to gum up. Two vehicles are said to have covered over 150,000 Km and two over 200,000 Km without any known occurrence of this problem, or any other major problem.
13 Durability—Directors are advised that in the test programs, more than 30 vehicles have been converted to Liquid Injection over six years with some 3,000,000 Km covered in road testing. The results have been excellent, with nothing more than to be expected electronic integration problems. As above, 200,000+ Km in two vehicles. Vapour systems tend to gum up the vaporiser from the heavier, gooey elements of the LPG left behind. Replacement of the vaporiser is the usual result and is expensive. Liquid Injection does not allow this, as the liquid is squirted through the injectors and they stay clean. Fine metal particles, which reduce efficiency in gas injectors, simply wash through Liquid Injection injectors.
14. Compatability—Catalysts and Liquid Injection are compatible as in multi-point petrol injection, for the same level of control is possible. Only the liquid injected is changed. Hence there is no more variation in fuel mixture than with modern petrol systems and catalyst life is not threatened.
15. Backward Compatability—Switching from Petrol as in item 6 above, Liquid Injection is the best mono LPG system. It can be, simply and cheaply, converted back to petrol by a qualified mechanic replacing the LPG filler pipe with a petrol filler pipe, then you have a closed loop system for petrol. This closed loop system for petrol is covered by an Australian patent, No: 672495.
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