What is Common Rail Injection?

[Briman]

Can someone give me a brief tutorial on how it works. Does it use a VP44? Is it better than the previous 24v setup? Does it use the same lift pump? Thanks for your input.

 

[bighammer]

Instead of a pump acting as pump AND distributor, the common rail system has a pump that pressurizes a tube (common rail) that feeds all the injectors with an eqaul pressure all the time. The computer triggers the injectors to open and close to control timing and duration of injection.



This is my understanding of it anyway. I'm sure there are some folks who know a lot more than I do.

 

[Briman]

Is it a mechanical pump mounted where the vp 44 was located? If there is a mechanical pump is it still fed by a lift pump (it sounds like it when I turn the key)? Are the injectors electrically activated like on a gasser. Are the electrical connections for the injectors under the plastic cover on top the valve cover? What else can you all tell me... . ?

 

[jwilliams3]

Your 03 Cummins has a Fuel transfer pump located next to the fuel filter canister, it is black and about the size of a roll of silver dollars (maybe a little bigger).



The Bosch Common Rail Fuel Pump CP3 is located in the same area of the VP44. It is mechanically driven but not timed to the engine.



The reason for the black plastic vanity cover is for shelter of the crankcase breather bottle which resides under it.

One tube returns oil to the crankcase (small one) the other is the air tube for releasing air pressure (blowby).



The electrical connections for the injectors are located at three points on the fuel side of the engine.

Look at the aluminum platform above the Head and you'll see 3 electronic plugs, one in the middle of every 2 cylinders.



Any more questions?



--Justin

 

[jlevesque]

fuel comes from the tank to the lift pump, to the filter, to the two

stage high pressure pump( first stage approx 200 psi to second stage 5000 psi at idle up to almost 26000 at full throttle full load,

to common rail, to ecm(computer) controlled injectors that operate

at up to 90 volts. the system uses numerous inputs to determine

injector pulse with and timing, crank sensor, cam sensor, apps,

fuel rail pressure sensor, inlet air temp/pressure sensor, intake air

temp/pressure sensor, coolant sensor. 70% of fuel supplied to the

injectors, returns to the tank for cooling purposes. there is a fuel control actuator, mounted on the high pressure pump( cp3) that

controls the amount of fuel to the high pressure side of the pump,

which = amount of pressure to rail.

the ecm used is manufactured by motorola and operates at 40 mhz, this is the fastest computer chrysler currently uses.



hope this helps, if you want more detail etc, let me know?



James

 

[jimnance]

I'm confused. On another thread about the Edge EZ they said the EZ worked by boosting the fuel pressure. If the fuel pump is mechanically driven then it seems like the Edge must be working by altering fuel timing and duration via the ECM??

 

[bighammer]

I think the pressure of the common rail is also controlled by the ECM.

 

[jimnance]

If that's the case Big Hammer, then it seems that much more performance and economy can be achieved when they get a handle on altering the fuel timing and duration.



I'm sure the stock timing and duration is a compromise between performance and the need to meet emissions standards.



With my old EZ I saw about a one MPG increase in mileage. I doubt by just boosting rail pressure they will enhance economy. Seems like those improvements will come in later versions of the Edge or other performance enhancement box.

 

[jwilliams3]

jimnance,

Raising fuel pressure in the fuel rail will increase fuel delivery.

This is done by fooling the ECM into thinking rail pressure is low.

Then the ECM tells the pump to increase delivery, and if injection and duration stays the same fuel delivery will increase.

If I remember right one of the connections of the EZ's wire harness connects to the common rail pressure sensor.

Of course its not all as simple as it sounds.



--Justin

 

[bighammer]

Thanks Justin. I thought I had heard that from somebody (maybe you?)

 

[waterdonkey]

So the injectors are fired and controlled by the 90V current. Is it safe to compare the high pressure fuel rail to a EFI system in a gasser with just higher pre injector PSI in the rail?



I just want to know if it is completely different from the Ford PSD with the oil pressure fired/controlled injectors.

 

[rbattelle]

Rest assured, it's QUITE different from the Ford system.

 

[Parshal]

Originally posted by jwilliams3

jimnance,

Raising fuel pressure in the fuel rail will increase fuel delivery.

This is done by fooling the ECM into thinking rail pressure is low.

Then the ECM tells the pump to increase delivery, and if injection and duration stays the same fuel delivery will increase.

If I remember right one of the connections of the EZ's wire harness connects to the common rail pressure sensor.

Of course its not all as simple as it sounds.



--Justin

Also, Bryce, at Edge, said that the ECM will alter timing as well with the change in rail pressure due to the EZ.