[CNGBiFuel]

I kinda grasp that CR is dependent on far more than fuel, combustion chamber shape and no least what the chamber can take with a full chrge of fuel and air. But it's been a long time since i read up on this stuff, I'm an electronics engineer, no motor tuner! I'm worried about hassling you but please a few more related Qs?

1) Am I correct is saying the reason LPG needs more advance than petrol, and CNG still more, is the slower flame-front.
2) Both are harder to ignite in the first anyway, correct?
3) But if this so, why am I told they run hotter, when I would expect cooler, or is it that once alight the flame is hotter?
4) In the ideal engine, one that only runs on one of the gases, removing any comprmises to run petrol, how would this 'ideal-engine' differ?
5) So a little bit of where I came in... no matter how much I thkweam and thweam, in three theoretical engines, Petrol; LPG; CNG, each optimised for its particular fuel, 'theoretically' we will never finish with the same power with the gas fuelled engines because no matter what else you do, the density of hte gases, means that per cycle the gas-engines will never able burn as much energy, simply because you've less room for the oxygen needed to burn it.