Please indulge me if I seem to be teaching people how to suck eggs, a little bit of theory behind internal combustion engines is needed here. Please forgive me if I get it a bit wrong, I'm trying to remember this from lessons I was taught many years ago with a few quick peeks at some books to try and refresh my memory
Petrol/Gasoline engines use a highly volatile fuel, they work by pumping air into the chamber and the fuel is dragged along with it creating a fuel-air mixture which is then ignited by the electrical spark causing it to basically explode for want of a better term. The resultant combustion causes pressure that forces the piston to move. The proper mix of air to fuel is important to prevent unburnt fuel from being dumped via the exhaust system or too much fuel flooding the chamber. Later engines use fuel injection, forcing an aerosol of fuel into the airstream.
Diesel engines work by compressing the air in the chamber to superheating (typically 550 degrees C or more) then injecting the fuel in very fine droplets. The heat of the air causes the fuel to vapourise. The vapour then burns and thus builds up the pressure and forces the piston to move.
Because of this, any mix of fuel can be dumped into the same fueltank and the way the engine works will ensure the fuel burns. Unfortunately if the two fuels don't mix well, a slight delay can occur in the cyclinder when changing over to the other fuel type (typically the lighter fuel gets used last as the heavier will be the first to enter the fuel line due to gravity)
Multi-fuel diesels don't use any new technology, they revert back to the original technology which was crude enough that it didn't need any changes to be made to the timing cycle to allow it to burn any suitable fuel.
Early diesels used a glowplug to start the initial combustion cycle now they tend to use electronic ignition.
From what I understand of it, the more sophisticated diesels (e.g. electronically controlled injection and electronic ignition types) are more sensitive to fuel differences and require timing changes to ensure correct piston height/compression to control air temperature and so on when the fuel is introduced.
|