Benz Common Rail

[JoshPeters]

Good stuff! I just finished my update training. We spent almost an entire day on this engine. Lots of interesting stuff. I would immagine that Cummins uses some of the same logic.



The system can use up to 3 pulses to inject the "required" ammount of fuel. If it uses one or 3 they will all add up to the same ammount.



There is a fuel pressure regulator, and a fuel quantity control valve to control fuel pressure.



If the fuel temperature rises, it will lower the fuel pressure till it returns to normal. If the temp doesn't lower it will reduce injection quantity.



It has a Mass air flow sensor, but it is only used for EGR control.



The EGR has a gas to liquid cooler to help lower the return gas temps.



It is a Direct injection system



It uses glow plugs in the cylinders





The glow plugs only glowed for approx 2 seconds at 45 degrees! They us an initial spike of 12 volts to get them started but drop back to 6v within about half a second.



Just thought I'd share some of my learning expierence with you guys. Especially since there was a write up on the 320CDI in the last TDR mag.



Josh

 

[Wayne M.]

Would I be safe to say that that engine uses Bosch Common Rail? And that this system is the same in all applications with the difference being the amount of cylinders and other particular items like glow vs. heat grid? Of course I am refering to the 3G engine. Whenever I see a Bosch CRD system I always see that fuel manifold next to the cylinder head, regardless of engine.

 

[rbattelle]

If the fuel temperature rises, it will lower the fuel pressure till it returns to normal. If the temp doesn't lower it will reduce injection quantity.

That is a very interesting fact. I wonder if the 3rd gen truck's Bosch system does the same thing.



-Ryan

 

[JoshPeters]

Would I be safe to say that that engine uses Bosch Common Rail? And that this system is the same in all applications with the difference being the amount of cylinders and other particular items like glow vs. heat grid? Of course I am refering to the 3G engine. Whenever I see a Bosch CRD system I always see that fuel manifold next to the cylinder head, regardless of engine.

It is a Bosh system for the most part, but like Dodge, Cummins or Benz I'm sure Benz said they wanted the program "this" way. All the parts we looked at had Mercedes part numbers on them, so I am not 100% on that one. Bosh could build them and put Benz numbers on them.



On the 3rd Gens do they have a fuel pump in the tank? This particular car uses almost a gasser type set-up with the pump in the tank pressurizing the system up to around 40psi.



Josh

 

[David Oxland]

I read recently that, new on the design table for Bosch, is that they are developing a common rail injector that uses the piezo principle rather than electromagnetic for piloting the injector. Was this by any chance involved with the MB?

 

[CChase]

On the 3rd Gens do they have a fuel pump in the tank?

The 05's do. The 03s and 04s did not.

 

[JoshPeters]

I read recently that, new on the design table for Bosch, is that they are developing a common rail injector that uses the piezo principle rather than electromagnetic for piloting the injector. Was this by any chance involved with the MB?

That may be very possible. They did mention at school that this engine will be around for a while with a couple changes to come. They would not tell us anymore about what the changes are. A piezo set-up would be much more accurate. Right now they are basically using a solonid to change the passageways in the injector so it opens. Trying to explain this without the pictures is tough. The injector has passages around the pintle that goes down to the nozzle. Around the pintle is a spring with a TON of tension (I don't remember the spec. . I have it written down) With the passage blocked to the bottom side of the injector it can not open, but there is fuel at the tip. When the solonoid opens the passageway it uses the help of the spring to push the pintle up and allow fuel through. There is a bit more to the solonoid part of that, but that is the basic function. They told us "If there is a problem with the injector, remove it and replace it. DO NOT take it appart. "



Josh