In the general diesel forum, a few guys were mentioning that our 7.3 was a common rail system. I didnt think so, but I did realize Im not very schooled about it.

Anyone have some good info or reading about this?

(heres the thread I was referring too if anyone is interested https://www.ford-trucks.com/forums/8...-source-4.html)

 

Here's a brief explanation of what "common rail" means. http://www.swedespeed.com/news/publi...inter_272.html ''Common rail" generally refers to the fuel being compressed at a high pressure in a rail, shared by all, before the injector, where as the fuel is compressed, individually, in each injector of the powerstroke.

 

Not a common rail like the Cummins, but each head does have a common rail for the fuel to feed the injectors.

 

Our trucks are NOT common rail. The dodges and Chebbys are. Also the 6.4 PSD's are too. It is a more efficient method of injecting fuel into the motor.
We use an HEUI. hydraulic electronic unit injector. Basically we use high pressure oil to squirt the fuel into the cylinders and Common rail uses high pressure fuel.

This is the way I understand it. Please correct me if I am wrong.

 

I thought it meant that a common rail fuel system didn't dead-head; which causes trapped air and low pressure at the end of the fuel line. That's why I thought some of the regulated returns were making our fuel system a "common rail" by linking to the two rails together. It's also why I thought some of the mods that link the two injector oil rails together...to balance/equalize the rails. I assume there's two rails: oil and fuel.

I knew the Cummins was a common rail, because it is an inline design. The Power Stroke is a V, therefore needs two of everything.

...I could be all wrong about this and adding to all the internet myths and lore.

 

Just a note, fuel as a liquid can't be "compressed", but pressurized.

Common rail injection systems are more responsive and can typically flow better. I think some of the differences are that in a CRI, there is an electronic or otherwise actuated injector right at the head. It only meters fuel to the cylinder. All the injectors are fed from a high pressurized and pressure modulated fuel rail.

Other systems use a poppet type injector at the head and the fuel is distributed directly from an injector pump through an individual fuel line. Or in the case of the 7.3/6.0 a large hydraulically boosted injector. The heui is slow, and has limitations, and flow restrictions. The 6.0 is a little more responsive because of it's on and off solenoid vs. the 7.3 poppet style on only solenoid.

The limitations on the injection pump system is overcoming the poppet in the injector, poor flow and poor response/control (relatively speaking). Pressure has to build in the line for every injector every time the cylinder fires. The HEUI is a large unit with a lot of internal mass that places control of the fuel closer to the cylinder and reduces the need for lots of high pressure connections and lines external to the engine, but still doesn't have enough response. CRI and the latest in the 6.4 uses a highly responsive electronic injector and gives much more precise control over the injection event (or multiple injection events per firing). It's volume is probably only limited by nozzle size. Fuel should flow as long as it's commanded open, unlike the HEUI which has a limited injection stroke.