EcoBoost F-150 Direct Injection Explained

First, we had carburetors. Then came along throttle body injection. Port injection followed soon after and was a major success. Nowadays, most manufacturers are adopting the latest fuel delivery technique of direct injection, particularly for turbocharged applications.

Albeit, direct injection is not something particularly new to the automotive world. The concept has been around for decades and has been widely used in the diesel engine market for quite some time. However despite being a known technique, it is only recently that we have seen a noticeable and widespread shift from port injection to direct injection across all manufacturers.

In regards to the F-150, the introduction of the EcoBoost engines back in 2011 simultaneously featured the first use of direct injection in the F-150 truck lineup.

When port fuel injection first became widely adopted, it was a big deal. It was a major step forward in terms of fuel delivery, and also for automotive electronics. It signified the fundamental computer-controlled basis we see applicable to all the F-150s of today. Gone are the mechanical cables and linkages and instead we now have an engine control unit (ECU) making thousands of calculations a second to operate the engine. With the electronic injectors controlled by a computer, fuel delivery could be more precise than it ever has been before and forms a strong argument as to why engines are as reliable and capable as they are today.

It no longer mattered what the temperature was outside, or what altitude you were at; the computer would take it all into account and calculate the necessary fuel actions to make for easy starts, smooth idles, and great operation every time you turn the key. Direct injection takes everything port injection has to offer and improves on it. Better power and fuel efficiency are just a few advantages of direct injection. We'll examine it shortly.

Port injection is pretty simple. Operating at pressures between 40-60 psi, one end of the fuel injector is connected to a rail, which supplies a constant stream of gas. The other end, the nozzle, is screwed into the intake manifold runner. When commanded to by the ECU, the injector activates and sprays a mist of fuel into the manifold (for example, at 2000 RPM, the injector is cycling approximately 17 times per second). When the intake valve opens, the mixture of air and fuel whooshes into the chamber where it is then ignited. 

One disadvantage of port injection is there are some inefficiencies which translate to decreased fuel economy. For example, even though the fuel and air mixture does not stay for long in the intake manifold runner, it is still there for sufficient time for some of the heavier fuel to drop onto the bottom of the runner and consequently not make it into the combustion chamber. Multiply this by each cylinder and the number of intake valve events over the course of a mile and there is a noticeable effect on fuel economy.

Direct injection eliminates the middleman that is the intake runner and instead sprays the fuel directly into the combustion chamber. The fuel injector is still connected to the main rail, but the nozzle is no longer screwed into the lower manifold. Rather the nozzle is now installed directly into the cylinder head itself with the tip protruding into the combustion chamber. Because fuel is now sprayed directly into the chamber, there is no fuel wasted like there was with port injection, and the fuel events can be further controlled with the precision that has never been seen before.

Spraying the fuel directly into the chamber lowers the temperature allowing for a higher compression ratio, which is better for combustion and makes more power. Direct injectors operate at pressures of several thousand PSI, which produces optimal fuel atomization to mix with the incoming air charge. In short, fuel efficiency is increased (by as much as 15%) and so is overall power. Direct injection, in conjunction with the turbochargers, are a major reason the 2.7L and 3.5L EcoBoost engines are able to produce the power that they do, and also produce the surprisingly good fuel economy numbers despite having to move a ½ ton truck (which in reality, despite the ½ moniker, weighs close to 5000 pounds).

• Decreased combustion chamber temperatures 
• Increased compression ratio
• Increased power
• Better fuel efficiency 

Because the fuel is no longer entering past the intake valve, the fuel cannot act as a cleaning agent (as it does with port injection). Thus, some early model EcoBoosts experienced idling problems as carbon built up on the intake valve, most noticeable upon a cold start (where the very rich mixture needed for a cold start would wash down the cylinder walls, decreasing burn efficiency and increasing emissions and carbon buildup). Once the engines were brought to operating temperature, the problem would disappear, and thus made it very baffling for many owners.

The approaching year has some very neat features coming to the F-150. The 3.5L EcoBoost engine has been redesigned nearly from the ground up. This second generation 3.5L V6 EcoBoost will feature a brand-new hybrid fuel system composed of both port and direction injection. By utilizing both methods of fuel delivery, we get the best of both worlds. Port injection will be used for cold starts and low loads whereas the direct injection system will take over once the engine has reached operating temperature or is under high load. Although it is a more complex system (nothing gets simpler these days) the advantages are obvious. 

​Maximum power and fuel efficiency, minimal emissions and the elimination of carbon buildup. This motor, set to produce 375 horsepower and 470 ft-lbs of torque, coupled with Ford's (actually co-developed with GM) all new electronic 10-speed automatic transmission should make for one beast of an F-150.