I think that how long it takes to catch fire is in the order of a couple of milli seconds but i would have to do some calculation on that but it varies with fuel it is called ignition delay.

Years ago they used to use diesel to start the engine but with moderm materials and method we circulate the fuel to keep it at a high temp as we preheat it before putting it in the engine. the fuel is heated to about 120 centigrade but that is an approx figure as we measure the viscosity and control on that instead of temp. That allows us to get the fuel thin enough to atomise under injection conditions and then burn effiecently

As to the effiecency that is due to many things like waste heat utilisation and long stroke engine and other factors that i am not too sure of and the turbo chargers are incredably effiecent in comparison to automotive type ones

If you can download that PDF file i pointed to it make some intresting reading.