common rail diesel injectors?

I'm a computer programmer, not a mechanical engineer, so I came here to ask a couple of diesel questions. These new fangled electronically
controlled diesel engines with a common rail and direct injection... is the pressure in the rail up in the thousands of pounds, or just in the injector nozzle as it injects? Is it a mechanical pump, or electrical? How much power does it take to get that pressure? Couple horsepower? Is there an accumulator or a bypass valve, or does it just pump all the time?Are the injectors electrical? (I assume they are solenoids, right?) Wondering how much power it takes to operate them... volts, amps, watts, etc. How fast do they actuate? 1ms? 10ms? And finally, last question, if you can bang the injectors open and closed with big electromagnets, why not do that with the valves too?
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The pressure in the rail feeding the injectors is around 1200 to 1500 bar [not psi] which is around a high of 21750psi if I am not mistaken.

mechanical
How much power does it take to

Not a lot I would have thought because the volume is low.
Is there an accumulator or a

Not sure but I believe it is a variable displacement pump.
Are the injectors

Never gone in that deep but google for Bosch injectors and you will find much knowledge.
And finally, last question, if you can bang

The injectors only actuate fractions of a mm and up to five times in an injection cycle using something like piezzo actuation. Try 'how stuff works' or Google to get in-depth information.
Huw
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Thanks for the fast reply!
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Huw wrote:

FWIW, I don't know of any mass produced engines using direct electrically-operated injectors. Too bulky, too much electrical power draw, too noisy, and frankly too much non-linearity to correct for in software. A very clever approach that many manufacturers have taken is to operate the actual injector HYDRAULICALLY using engine oil pressure. A much smaller and lower-power electrical solenoid under computer control is used to modulate the oil flow that controls the injector. Its the best of both worlds- an easy electrical interface for computer control, but with manageable size solenoids and current draws since the hydraulic fluid does the heavy work.
When this system first came out YEARS ago on heavy engines, Navistar International was one of the pioneers with their "HEUI" (Hydraulically-actuated Electronically-controlled Unit Injection). So you might google around on that term for more information. Since its all kinda old-hat now (although still "new" to passenger car applications) Navistar probably isn't still bragging about it so much on the front of their website.
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Don't all these monstrous duallie pickups have electronic diesels in them? Thats what the superchip guys are messing with right? Keep squirting 4 or 5 times as the piston goes down to keep the fire burning and the pressure up?
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BobG wrote:

The Ford Powerstroke is a re-badged Navistar with HEUI (hybrid hydraulic/electronic injection), and has been ever since they started calling it "Powerstroke."
The Cummins in the Dodge has been fully electronic since about the time they converted it to the 24-valve layout, and as I understand it has a very advanced injection profile, which is what you're probably referring to. I don't know that it squirts multiple times, but it does start with a "pilot" dose of fuel and rapidly ramps up to the main shot, which is what virtually eliminated the diesel "rattle" from that engine. Its by far the quietest heavy-duty diesel I've ever heard in its latest version. It sounds more refined and less like a typical diesel than the VW TDI passenger car diesel, for that matter.
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I have no experience of big US pick-up trucks but do know that the excellent Cummins B series tractor engine is available in a Dodge. The last version used a 24 valve hi tech unit which uses an electronically controlled rotary Bosch electronic VP44 fuel system. The VP44 system controls the timing independent of speed, which is key to meeting the 1998 emissions levels. The Bosch system is electronically integrated with the electronic control module (ECM) of the Cummins engine. The ECM controls the Bosch system fuel pump. It uses conventional injectors centrally placed between the valves with a design similar to my light duty Toyota 4.2 1HDFT-E engine installed in the big Land Cruiser. Although a high pressure system it is not a system likely to survive the next series of emission regulation, confirmed by the introduction of the new 610 which has high pressure common rail injection system, probably a second generation system with around 1500bar pressure A 'common rail' fuel delivery system is one that maintains a high injection pressure regardless of engine speed, using high-pressure fuel stored in a single "common" rail or tube that connects to every fuel injector on the engine. http://www.everytime.cummins.com/every/misc/brochures.jsp#Dodge%20Ram then download from the 'medium-duty trucks' section the two first documents in the list for an engine overview. See here for an overview of the various current state of the art injection systems. http://www.boschusa.com/AutoOrigEquip/Diesel/CommonRailSystem /
Much of the technology, such as common rail, variable geometry turbochargers and cooled exhaust gas recirculation has been common practice in light passenger vehicle engines for some considerable time, even for vehicles built in the USA for export to Europe and Australasia. I am thinking in particular of the Mercedes ML270CDi and the BMWX5 3.0 diesel, both vehicles now on their second generation of engines with this technology.
Huw
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Huw wrote:

The "610" version of the B5.9 (named for its torque rating) has been the version offered in the Dodge Ram for at least 2 model years now. I forget the exact progression, but the revamped engine lineup started in about 2002 (the year of the big re-styling of the Dodge truck line). It may have been 2003 or even the '04 model year before the "new" style truck with the "610" diesel became available. As Ford does with their light trucks whenever there's a re-style, the Ram 1500 got the re-style first (with the 3.7L v6 and 4.7L v8 gasoline engine and for a time the legacy 5.9L, which was replaced by the 5.7L Hemi) and was sold concurrently with the previous-style Ram 2500 and 3500. Then about a year later they released restyled versions of the Ram 2500 and Ram 3500, which got the new 610 diesel to replace both the old Bosch-injected 24-valve diesel and the gasoline V10 options. I'd have to go look to see if they still de-rate the engine for use in front of an automatic transmission as they did for a number of years- I don't *think* they do anymore.
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wrote in message Are the injectors

Tell that to BMW, Mercedes, Ford, Fiat and many others which use common rail with electronically controlled injectors.
A very clever approach that many manufacturers have taken is

These are oil over oil injectors commonly called 'unit injectors' because they are injector pumps and injectors combined. These are fed from a relitively low pressure rail, distinct from high pressure 'common rail'. This type is used in various forms by heavy truck engines such as Volvo and Caterpillar. Also used by Land Rover in their TD5 engine and with less success by Isuzu in the now defunct Trooper [Bighorn] 3.0 direct injection engine.

I believe that Caterpillar held most patents involved with this type.
So

It may be new your side of the pond but both CR and UI are very common here, especially CR;-)
Huw
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Huw wrote:

Well, thats why I said "FWIW, I don't KNOW of..." ;-)
And are all those systems actually direct-acting solenoids, or are they hydraulically actuated but electronically controlled?

I don't know who held the patents, but Navistar certainly put it out there in big numbers before Cat did. One of the few times another Diesel maker ever trumped Cat at much of anything.

There ARE no diesel passenger cars made on "my side" of the pond at all, and only a handful sold here :-) There was a pretty long stretch of years until the TDI came along when there weren't even ANY sold here.
I do get amused at the advertising for light-duty diesel engines (car, truck, tractor, and otherwise) that make a big whoop out of things like common rail and unit injection as if they were new and wonderful. They may be new to itty-bitty diesels, but the engineers at EMD, FM-Alco, GE, etc. have to get a pretty good laugh since they've been doing things that way for decades.
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wrote in message Are the injectors

I could add GM in Europe to the above list. That is one hell of a lot of engines you don't know of. In fact around 45% of cars sold in many European countries are now diesel with the vast majority of new ones being common-rail type.

Common rail injectors are all direct acting solenoids with the latest being of the piezzo type with multiple injection stages per firing stroke.

You are wrong here. Both Mercedes and BMW manufacture diesel cars in bulk in the USA and export them to Europe and elsewhere.

European cars have used common rail from the outset of the technology. You seem distinctly foggy about how they basically work considering your last statement above. It is only comparatively recently that medium and heavy engines have caught on. Unit injectors and unit pump types have been used in heavy truck engines for somewhat longer. Only now are medium size engines catching on to common rail as recently introduced by Cummins and John Deere.
Huw
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So the 1st squirt is into 22 bar hot air. Once that lights off, the cyl pressure jumps up to 1000 bar or something, so if you want to inject again into that, you need a real head of steam behind the injector, right?
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The main impetus is to meet increasingly strict emission regulations and noise regulations combined with refinement, economy and low service demands by the consumer.
Huw
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I dont see any connection between the last two messages
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BobG wrote:

Since you didn't quote them, we don't know which two you mean. What the last messages were is entirely up to when you download them. This will be different for every reader.
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BobG wrote:

That's true of ANY diesel, because even in the most ancient injection-pump system, the fuel continues to be injected AFTER combustion begins.
With a common-rail system, it additionally means that a larger volume of "plumbing" has to be pressurized to a level greater than the engine's cylinder pressures, and has to be maintained at that pressure constantly rather than just during an injection event. The advantage is finer control over the injection profile.
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We had an interesting debate about tuning in sci.energy... got different answers on whether tuned exhaust and tuned intake would benefit scavenging and induction on a diesel. The idea was to supertune one of those 3hp chang-fa chinese 1800 rpm diesels to minimize fuel consumption at that one specific speed, and control the load on the shaft (field control on an alternator) to not load it and pull it out of its tuned speed range. Didnt get any real clever tuning ideas. You automotive types have any tuning tricks up your sleves? Does tuned exhaust do anything on a diesel?
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BobG wrote:

Tuning does the same thing on a diesel that it does on any other valved combustion engine- improves scavenging and improves volumetric efficiency at a particular speed, usually at the cost of lowering VE and scavenging effectiveness at other speeds.
Since diesels are direct-injected with no fuel in the incoming intake charge, its usually preferable to depend on positive boost pressure (either from a mechanical blower or turbocharger) to to flush a bit of fresh air through the cylinder during the valve overlap, rather than use tuned intake/exhaust for scavenging. The result is thorough scavenging over the entire operating RPM range, rather than just one speed. Over-blowing of this kind is especially beneficial (in fact, necessary) for 2-stroke diesels which rely entirely on scavenging to clear out the combustion byproducts.
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2000bar injection pressure is imminent. That's over twenty nine thousand pounds per square inch of pressure. This kind of pressure is certainly not to overcome cylinder pressure.
Huw
Huw
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huw says: This kind of pressure is certainly not to overcome cylinder pressure. ====================================================I dont understand this sentence. What is this hi pressure for again?
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