what is direct injection?

What exactly is this? allegedly porsche is already working with it for future models, and according to a recent felisa interview, ferrari may as well...BMW uses it I think on there 06 3 series...anyone know what it is exactly?

 

Direct injection means that the injector shoots fuel directly into the cylinder rather than through the intake manifold and valves.I believe that air will then be introduced through the intake valve then mix with the gas.
Go here to see how it works in a diesel http://auto.howstuffworks.com/diesel.htm

 

Mitsubishi have been diong it for a few years now on there petrol engines,
instead of the fuel injector being behind the valve it's placed in the combustion chamber like a diesel realy,

Dale.

 

thanks guys, still wondering why it works better...

 

On a diesel, the injection pressure is very high and creates a very fine mist. This allows for more complete combustion.

 

Several years ago Toyota published some SAE papers on using DI with lean-burn engines. Lean burn is using less fuel than the stoichiometric ideal for the amount of air in the cylinder. In theory DI allows you to place the fuel in the cylinder head where you want it (by the spark plug) to achieve combustion, but overall the average air/fuel ratio in the cylinder is less than would be possible with coventional upstream injection. Fuel economy and a reduction in certain types of emissions were cited as the benefit.

It has been about ten years since I read about that, though. Probably a lot more has been done since then.