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Want a common rail?
Here ya go... http://www.kfz-tech.de/Bilder/Kfz-Te...mmonRail02.gif Here's a pic of the 2.7 CDI in the Sprinter. http://i12.ebayimg.com/01/i/01/14/85/a2_3.JPG |
More, more more!!! The picture is great, but it has raised more questions. On traditional diesels, isn't timing controlled by the injection pump? What controls the timing on CDI's and if the whole rail is pressurized, what causes the injector to ejaculate at any given time?
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Computers control everything. 20K psi is what the new CDI's are pushing now through the common-rail. The CDI's are direct injection, and the computers control the solenoid operation of fuel flow. So the fuel pours through the common rail, and goes straight through the solenoid valves, out the nozzles of the injectors, and straight into the chambers to ignite the fuel by compression. Baddabing.
In a bad sense, though, if your altenator decides to quit on the highway, you're stuck. Engine stalls. I drive my old diesels because I know, once they're running, they won't stop unless I make them, no matter what. |
By electronically controlling the injection of fuel into each cylinder, injection timing can vary depending upon load, temp, rpm, etc. But the best is yet to come. The circuitry that is controlling the injection is designed so that fuel is delivered at a different pressure/rate during each injection event. This is what vastly increases output and efficiency and reduces the telltale 'diesel' knock'.
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Click here I found this site to be extraordinary. |
By electronically controlling the injection of fuel into each cylinder, thats one more electronic thing we will depend on and hope never fails. Just like our wonderful cruise control amps, climate controls, tach amps, and EDC systems.
Like DslBnz said, I think of our OM617's not using electric except to start as a safty feature. I've seen the reports of sprinters just stalling for no reason. Have they decided what costly (And probably electronic) part needs to be replaced to fix that? |
Where exactly is the solenoid that controls injection on a CDI engine?
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http://members.aol.com/jzettel73/Injector/Solenoid3.jpg |
Yeah, you can rebuild those yourself :rolleyes:
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Imagine a fifty year old CDI engine with original common rail injection system? Yeah right.:rolleyes: I saw a peagreen W115 240D the other day and he passed me at 80 + mph! I couldn't believe it! How fast do you need to go? 67 hp is enough to get you a ticket on the interstate for reckless driving. |
Do the CDI's use cylinder sleeves that can be replaced on rebuild? Are the solenoids wear items that must be replaced over time much like the older injectors? Does it have the 6ft long glow plugs like the OM606 ;) ?
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To correct an earlier post, CDI means Common rail Direct injection. These engines don't use prechambers - the fuel is injected directly into the cylinder.
They also use pilot injection - a very small quantity of fuel to start the combustion process, followed by a larger injection to provide the power. This greatly reduces the telltale Diesel "knocking." One of the manufactures (I forget whether it's VW or MB) uses up to 5 injections per combustion event. These engines have 4 valves per cylinder, not because they need the better breathing, but to allow central location of the fuel injector. Such precise injection also enables much better cold starting. For example I was able to start my Jetta TDI at 8 degrees Farenheit with less than a two second wait for glowing. The engines are also extremely efficient - the VW does not make enough waste heat to warm itself up, let alone the cabin, without a load on it. The MB E320CDI is reported to top 40 mpg, and is due here soon. The Jeep Liberty is also supposed to get a CDI engine this year. |
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