Direction Fuel Injection vs. Port Injection

Today’s automotive manufacturers face tremendous pressure to deliver vehicles that are cheaper in cost and better in performance.  Auto makers must meet strict fuel emission regulations every year before their vehicles can be put on the road.  Direction fuel injection is a technology used in many of today’s cars to boost performance, lower emissions and improve fuel economy.

The question you have right now is: “what is direction fuel injection anyways?”  Firstly, there are two methods of injecting fuel into gasoline engines: the conventional port injection method, and the newer and modernized direct fuel injection method.

Both systems require precise computer control to inject the right amount of fuel into the engine at a given time.  The difference  lies in the location of where the fuel injectors are mounted at.  In port injection, the fuel injectors are mounted in the intake manifold before the intake valve where the air-fuel mixture resides.  Once the intake valve opens, it will pull in the air-fuel mixture into the cylinder for the combustion process.

In direct fuel injection, the fuel injectors are mounted right on the cylinder head, and fuel is directly sprayed into the cylinder where the fuel-air mixture occurs.  In other words, only air passes through the intake and eliminates the need of the intake valve in direct fuel injection.  This method allows more precise control of fuel air mixture into the cylinder; thus, optimizes the cylinder combustion.

With direct injection method, fuel injection can be controlled much more precisely.  In addition, because engine cylinders can reach an excess of 15,000 psi, the high amounts of pressure allows the injected fuel to synthesize and ignite almost instantaneously.

Performance doesn’t come without compromise.  Direct fuel injection costs more to manufacture.  Because the fuel injectors are mounted so close to the cylinder heads, the injector are exposed to extremely high levels of pressure (up to 14,000 – 15,000 psi).  As a result, fuel injector components must withstand much harsher environments compared to port injectors.

Compared to port injectors, the pressure introduced in the intake manifold only reaches up to 40 – 70 psi.  As a result, port injectors are much more simpler and cheaper to manufacture.  One of the draw backs of port injection is that fuel is injected behind the intake valve.  Depending on how long the fuel-air mixture sits in the intake manifold runner, fuel can leak out of the air.

With tighter fuel emission standards and increasing pressure from consumers, automotive manufacturing itself, is a competition arena.  Direct fuel injection is a perfect example of offering both increased in performance and fuel efficiency at an affordable price.  Today’s vehicles still use both methods of fuel injection, but with new technology and development introduced every year, it may not be too far in time before we see all vehicles out on the road equipped with a direct fuel injection system.

http://www.youtube.com/watch?v=qd90yHlmfS4

Sources:

1. http://thechronicleherald.ca/wheelsnews/26226-direct-vs-port-injectio