What is Direct Fuel Injection and How Does it Work?


  • Direct injection is similar to the old electronic multi-port injection systems and carburetors. All the systems get vapor fuel into the combustion chamber for ignition. However, direct injection has some key differences that set it apart:      
  1.  Direct injection has a of method of getting pressurized (up to around 2000 psi of fuel pressure, according to AASA know your parts) vaporous fuel (gasoline or diesel) into anengine's combustion chamber. This is accomplished by 'directly' injecting it straight into the chamber through a direct injector that is actually inside the chamber. Neither a carburetor nor a multi-port injector can do this. They both vaporize the fuel outside of the chamber and rely on the camshaft and valve system to let the fuel inside the combustion chamber.  

  2. Direct injection has the capability to stop blowing fuel out of the exhaust (because of difference one) if the system is precisely timed. The fuel is quickly injected into the chamber, and then immediately ignited. This is done fast enough to allow both air and exhaust valves to be closed while fuel is injected when the fuel is ignited. On the older fuel systems, many engines have to keep the exhaust valve open even while new fuel was coming in. This means the engine would literally pull fuel into the combustion chamber and blow it out the exhaust without using it.
  3. Direct injectors have traditionally had issues with gumming up combustion chamber and causing carbon build up. This carbon build up becomes a large problem when the injectors stop injecting, valves refuse to close, or the engine has predetonation issues (abnormally high pressure igniting the fuel before it's supposed to).  This is actually the main reason why direct injection wasn't able to be used in the past. But thanks to recent developments in technology, engineers have lessened/solved the issues.   


direct injection sys
                       example to how a direct injection system works   
                        (http://www.autoguide.com/auto-news/2012/12/should-you-buy-a-car-with-direct-injection.html)



The History of Direct Injection            Pros and Cons of Direct Injection            Opening page            Bibliography