LPG +petrol

Novel idea adding lpg to engine that is already using it's own fuel source, however if you are thinking of adding this idea to your own vehicle DON'T bother it will only cause heartache and ultimately a loss of money to your back pocket, lpg is a very volitile substance and can and does damage engine's .. to gain power and save money? does not work!! as more power requires more fuel (more money ) to be more fuel efficient less fuel less power (less money ) the 2 do not not equate , so we have to make a happy medium and ultimately be happy with what you have got..the best suggestion i can give is to maintain your engine to be the best it can be.. .. the tried and proven way's of better power and better efficiency comes in the forms of 1/ get the old exhaust out,get it flowing! extractors/ larger diameter exhaust systems ,mandrel bends,full flow mufflers, larger bore catalytic convertor if possible.. 2/ get it to breath !! open up air inlet system buy a K&N air filter, fit a snorkel,fit an aftercooler / intercooler , open up or fit larger bore throttle body's..
these things alone cost a little however they work !! they do not cause adverse reaction to the engine and do give you noticeable power and increased fuel economy without major modification

no thats not what i ment. what i mean is why cant you make an engine run off petrol but using compression ignition. btw i have a real diesel but at around or over 10:1 compression petrol engines ping, so they are igniting off compression so why the spark plugs?

I can't remember the fugures, but I think it goes something lke this - petrol and lpg require about 550deg to ignite, wheras diesel only needs about 380. The lpg injection on diesels does not get hot enough on compression to ignite, but it is hot enough to ignite the diesel which in turn ignites the lpg. If you have a high enough compression to consistantly ignite petrol or lpg, your egt's will go through the roof, with engine parts through the bonnet soon to follow.

My figures are guestimates, but I think the logic is correct

Cheers andrew

yes. i actually thought pinging was when the compression of an engine is too high and the fuel egnites early trying to force the piston against the engine. This is why we have high octane fuel, as the high octane has ( i suppose) high egnition temp so the compression of the engines gas does not set it on fire. So from this line of thought you could have a diesel engine running petrolium. I would love to know the answer to all this. Funny, you think you understand hoe engines work!!

Sadly i am old enough to remember Water Injection for petrol engines,,,, that was a total failure also!! Michael