Talk:Common rail

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Fuelling a Common Rail Diesel[edit]

So, does anyone know if it is possible to run such an engine using uk domestic heating oil, without needing any modifications or causing other engine problems?


Gordon Brown

I take it this is a joke question? Heating oil is a much different thing from diesel as far as I'm aware. Much heavier and thicker for a start. Unless you are actually running on light paraffin or kerosene. In which case you'll need a pre-heater, but otherwise it'll probably be ok...?
Oh yeah and you'll probably have to keep a fairly hefty envelope full of cash with you at all times whilst driving in case a police or revenue officer stops you and checks what you have in your tank. I presume you're asking because heating oil is a great deal cheaper than automotive fuel, partly because it isn't subject to the same level of punitive taxes - and is therefore totally illegal to use as motor fuel without a specific exemption being granted. (talk) 13:43, 29 January 2012 (UTC)

Peugeot 908[edit]

I think the Peugeot 908 LMP1 is something worth noting in this article. Unfortunately I don't QUITE have all the details on it and even then I'm not certain how much of it would be suitable to insert in this article. What does everyone else here think?

Bolt Crank

TDI and CDI[edit]

Dear Author,

Volkwagen TDI is not a common rail diesel. Volkwswagen will probably be starting to build common rail diesel engines from 2007. Source: volkswagen Holland. Regards, Elias

And that's what the article says, Elias... (talk) 09:54, 27 May 2008 (UTC)

How about Mercedes' CDI? They use it in many of their diesel cars.

  • DCI is already inthe article. See DaimlerChrysler.

ACamposPinho 23:25, 16 July 2006

Fuel rail[edit]

What is a fuel rail ?. --Mac 11:08, 28 June 2006 (UTC)

Main pipe carrying fuel.

And I believe the common rail was designed long before 1960 as there were Doxford engines were operating with common rail.

Common Rail vs. Unit Injectors[edit]

The first part of this article does not describe a common rail system as the term is used in the engine industry, but a unit injector system. A common rail system is an injection system where the fuel rail is held at injection pressure (1000 bar or higher) and the injectors do not perform any internal pressurization. A unit injector system does have a "fuel rail" but it is merely the passage that carries low pressure fuel to the injectors to be pressurized there. Calling this a common rail system to an engine designer will only lead to strange looks.

I don't know - probably no stranger than describing a gasoline direct injection (GDI) engine as running petrol...Jmdeur (talk) 17:57, 8 July 2009 (UTC)

leaky pump on the common rail[edit]

"""They were cam driven and injection pressure was proportional to engine speed. This typically meant that the highest injection pressure could only be achieved at the highest engine speed and the maximum achievable injection pressure decreased as engine speed decreased. This relationship is true with all pumps, even those used on common rail systems; with the unit or distributor systems, however, the injection pressure is tied to the instantaneous pressure of a single pumping event with no accumulator and thus the relationship is more prominent and troublesome."""

maybe it has a leaky pump on the common rail

Wdl1961 (talk) 18:43, 8 July 2009 (UTC)

I think the point is maybe more that as the CR system is capable of so much greater pressures, and includes leak-back regulators and the like, this is not so much of a problem. The pump may be capable of producing a peak pressure of 4000 bar at the engine's governed rpm (say, 5000). If the system is regulated to maintain a relatively constant 1000 bar at the injector inputs, then much of that will bleed back to the fuel tank instead. The effective pressure will only start to drop when rpm dips below 1250 (assuming a linear rpm:pressure relationship, which is probably false), which is well below the speed at which a typical CR diesel (turbocharged or otherwise) is producing it's maximum torque, let alone power, therefore it wouldn't be able to make use of the maximum fuel pressure in any case. If the engine idles at a rather low 625rpm, there will still be half the maximum pressure/flow rate available to the injectors, and a good quarter at start-up if the starter motor cranks the engine at 312rpm.
An older system which connects the pump directly to the injectors may not have this facility. The maximum pressure will have to be capped a bit lower (as the injectors are having to handle whatever comes out of the pump; CR ones can be engineered to not need to deal with more than whatever the regulated pressure is)... let's say 2000 bar at governed speed, of which the injectors may only be able to "use" 1000? Which means by the time engine speed falls below 2500rpm, the pressure and flow rate are already falling below the peak, and at the lower rpms only half or less is available, limiting the low speed output. And turbo-common-rail diesels are very much focussed on remarkably strong lower-midrange performance as well as higher peak power... A modern one of moderate tuning may fetch 80hp out of a 1450cc engine (vs 50hp from an older generation non-turbo model, and at lower rpm too (4000 vs 4500)), which is a nice upgrade, but has a much more noticable increase in torque - say, 185Nm at 2000rpm (and at least 75% of that from 1500 to 3000), vs 91 at 2800 (and 82-90 from 2700 to 3500). Much greater fuel flow rate at lower engine speeds, with the turbo focussed on providing extra air mass at those speeds to take advantage of it. (talk) 13:57, 29 January 2012 (UTC)

Article issues[edit]

Suggestion to improve readability for naive entry to the article

The following text from the body of the article could be moved to the top. It would provide a reasonably satisfactory single-paragraph statement of what common rail is. (this text is from the body. I didn't make it up)

The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high-pressure fuel. This simplifies the purpose of the high-pressure pump in that it only needs to maintain a commanded pressure at a target (either mechanically or electronically controlled). — Preceding unsigned comment added by 2001:DC0:A000:4:F120:DC44:41BD:709D (talk) 23:10, 2 February 2016 (UTC)

Two issues I noticed with this article.

1. The article describes Fiat's selling of the technology as a tactical error before claiming Fiat "had no choice" in the matter due to its financial situation. How is it a "tactical" error if it "had" to do it? Tactics would suggest Fiat had some choice in the matter and made a mistake.

2. The article claims the technology was invented in the 1960s, but then describes a number of implementations of the technology dating to the early 1900s. One or other is false, either what was developed in the 1960s was merely an improved, modern, version of the technology, or else the earlier implementations weren't common rail systems.

I don't know enough about the subject to answer those questions and would have to delete the claims (which would be a fair chunk of the article) if I made the edits myself, therefore I think it best to comment here. -- (talk) 14:07, 15 June 2010 (UTC)

Completely agree with point 2. How can the prototype (late 1960s) have been developed 50 years after the technology first entered service with Vickers (1915)? The article is bizarre. Also, could something be said about the manufacturing hurdles for Common Rail technology to have taken so long to be commercialized in motor car IC engines.JBel (talk) 20:50, 12 October 2011 (UTC)
The reason for this discrepancy is that when people research engine history, they tend to only research road car engines, ignoring the advances and technology in aviation and industrial engines. Mechanical common rail was in place on Doxford engines long before it was available in any vehicle. I don't know anything about the Vickers system, unfortunately. --Joffeloff (talk) 09:24, 15 January 2013 (UTC)

Introduction to the list in the section "Common rail today" is restrictive[edit]

The list in the section "Common rail today" shows the growing and wide spread use of common rail technology. However, the list is introduced as containing brand names of car makers using common rail when there are notable markets and manufacturers outside the car market that use common rail. The section needs some updating to be inclusive of the broader application of common rail. RockyCliff (talk) 03:52, 30 November 2010 (UTC)

wait wait wait[edit]

So ... was common rail developed in the 1960s? Or already in use in 1942, and the 19-teens? We surely can't have it both ways can we, unless that sixties engine designer tripped over and dropped his plans into an experimental time machine in the same lab? (talk) 13:58, 29 January 2012 (UTC)

Typical wiki - every individual fact is correct, but the whole is unreadable. If anyone wants to rework this, the main point for improvement would be to distinguish between types of engines (compression ignition / spark ignition, their fuel: diesel / heavy oil / petrol, and also the size and application: ships / large generators / trucks / cars). Andy Dingley (talk) 14:32, 29 January 2012 (UTC)

common rail vs direct injection[edit]

Since "common rail" is a type of Direct Injection, I think a better structure would be to have an article called "Direct Injection" (no such page exists currently) and "common rail" would be a heading under that. Then other forms of DI (ie non-common rail) could be included in the same article. Therefore I propose to rename this page Direct Injection and restructure so that common rail is a heading. 1292simon (talk) 14:05, 11 April 2012 (UTC)

care to provide a reason (as opposed to abbreviated obsenities)? 1292simon (talk) 15:01, 11 April 2012 (UTC)
    • OK, it's because you obviously don't have a clue about the subject matter (I've just read your edit history - you prodded Gale Banks because you hadn't heard of him) and you think that "direct injection" first began when you saw the bootlid label on a car in Gran Turismo. Andy Dingley (talk) 15:37, 11 April 2012 (UTC)
Just FYI you haven't provided any arguments to respond to the points regarding structure above. 1292simon (talk) 02:54, 12 April 2012 (UTC)
This merge is so inappropriate to anyone basically competent to work such an article that no further detail is needed. Sometimes a comment isn't even wrong. Thinking that it's both appropriate and necessary to merge common rail to direct injection (apart from your other recent merge suggestions) shows such a lack of knowledge about the topic that it's difficult to begin to address it. Andy Dingley (talk) 17:00, 12 April 2012 (UTC)

Should this "common rail" content be moved to a section within a broader "direct injection" article? 1292simon (talk) 02:54, 12 April 2012 (UTC)


  • Support Since "Common Rail" is a type of Direct Injection, I think a better structure would be to have an article called "Direct Injection" and "Common Rail" would be a section in that article. Then other forms of Direct Injection (ie non-common rail) could be included in the same article. — Preceding unsigned comment added by 1292simon (talkcontribs)
"Since "Common Rail" is a type of Direct Injection,"
It isn't.
Common rail refers to the mechanism by which fuel is delivered to the injector. Earlier systems used injection pumps, that had to organise both pressure generation, volume control and injection timing. Common rail systems isolate the functions of pressure pump and flow control, so that timing and volume are now controlled by a solenoid valve, rather than by the pump. It relates to aspects upstream of the fuel injector.
Direct injection refers to the combustion chamber design - injection takes place into the cylinder volume, rather than an isolated combustion chamber, as it does for indirect injection. It relates to aspects downstream of the fuel injector.
It would be a bad idea to merge this anywhere. It is a clearly notable topic in its own right. If it was to be merged anywhere, it would be least damaging to merge it to fuel injection or injection pump, but not to direct injection, combustion chamber, or combustion dynamics.
Andy Dingley (talk) 16:57, 12 April 2012 (UTC)
IMHO that's semantics. I meant "common rail injection systems" are a type of "direct injection systems", rather than the rail itself (the articles focus on respective systems, which are far more interesting than just looking at components like the rail itself, I am not suggesting to change this 1292simon (talk) 23:43, 12 April 2012 (UTC)
What's just semantics? "direct injection systems" is itself a nonsense. Direct injection is about where the injection happens, not the mechanism used to do so. Andy Dingley (talk) 00:02, 13 April 2012 (UTC)
AFAIK early Diesel engines used indirect injection and more recent direct injection systems are based on earlier gasoline direct injection developments, so there isn't much to say about implementation specifics of diesel direct injection besides the Common rail system.
On the other hand, Fuel injection#Direct injection section can certainly be improved. I would also like to see more proof to the statement that common rail is now used in gasoline direct injection engines; neither article gives any sources for that. --Dmitry (talkcontibs) 17:56, 12 April 2012 (UTC)
Ok. Do you also oppose renaming it "Diesel direct injection" (so that there is a consistent structure between the diesel article and diesel direct injection, it is not intuitive for the layperson that the main diesel direct injection is called "common rail")? 1292simon (talk) 23:48, 12 April 2012 (UTC)
I'm not going to defend Fuel injection. It's the usual wikicrap, written by US teenagers who can't imagine there is anything else other than a current production petrol car engine. In particular this sentence, "Throughout the early history of diesels, they were always fed by a mechanical pump with a small separate cylinder for each cylinder, feeding separate fuel lines and individual injectors" just screams - I can see three errors in there, just in that little bit. Andy Dingley (talk) 00:02, 13 April 2012 (UTC)
Common rail might be less intuitive to you than diesel direct injection, but they are not synonyms. Common rail is an established term in the industry, especially in regard to modern high-performance car diesels which even displaced gasoline engines in European car sales. --Dmitry (talkcontibs) 07:12, 13 April 2012 (UTC)
Thanks for the explanation, Dmitry. I was trying to get some consistency between the structure of the petrol and diesel articles, but it looks like I will need to rethink my approach. Cheers 1292simon (talk) 09:05, 13 April 2012 (UTC)
  • Mildly oppose I don't think that it ultimately matters, but you already seem to have working separate articles. They can be functionally connected by appropriate links. Potentially you could have a better product by combining them, but it is quite difficult to combine articles without spoiling the whole thing. A couple of unnecessarily split articles just require a bit of paging back and forth, but a poorly combined unit is simply a mess. I should say that if anyone insists on combination, let him demonstrate an attractive product first. JonRichfield (talk) 19:30, 20 April 2012 (UTC)

First Picture[edit]

First picture in this article it's a Multipoint Fuel Injection... — Preceding unsigned comment added by Rfguicacs (talkcontribs) 07:33, 1 June 2012 (UTC)

As stated by the above user, the image I recently removed is of a fuel rail used for multi-point fuel injection. The general fuel injection article explains the difference between the two better than I could, but mainly MPFI has a much lower fuel pressure than common rail injection, and the timing of ignition is less important since the fuel is injected into the manifold before the intake valve, instead of directly into the cylinder (or a prechamber). You can easily tell the difference, as an MPFI rail will have fuel lines going to exposed injectors that inject into the manifold, while a common rail system's rail will have lines going to injectors in the cylinder head. --Joffeloff (talk) 09:24, 15 January 2013 (UTC)
Thank you for elaborating. I have just started the process for renaming the file (File:Injector common rail.jpg). If there are other mis-categoried files in the Commons category, please do not hesitate to move them or ask help doing so. Thanks for the input! Ariadacapo (talk) 16:56, 16 January 2013 (UTC)

Electrical common rails[edit]

Common rail (or simply COM) is a term used in electrical engineering too to define common paths of currents in a circuit. The article should reflect this or a new article should be made. --Rev L. Snowfox (talk) 14:33, 26 December 2013 (UTC)


Lede currently [1] reads in part On diesel engines, it features a high-pressure (over 1,000 bar or 100 MPa or 15,000 psi) fuel rail feeding individual solenoid valves, as opposed to a low-pressure fuel pump feeding unit injectors (or pump nozzles). (my emphasis)

That may be true of car engines (of which I have little experience) but it's certainly not true of small marine diesels... and I suspect of small diesels generally. The still-common arrangement here is to have a single high-pressure injector pump with a separate high-pressure line to each injector. The injectors are little more than no-return valves, having and needing no power supply or control connections (apart from the high-pressure lines themselves, which control the timing and quantity by Pascal's principle).

Bosch A-type injection pump 001.jpg
Valmet361 mk1 bosch.jpg

You can see two examples of pumps for the system I am describing at right. The top one is on a six-cylinder engine. There are six high-pressure lines leading to six "dumb" injectors. The bottom is a three-cylinder engine. These pumps are sometimes called distributor pumps (and that should not be a redlink).

That, I have always assumed, is the reason that common-rail systems are called what they are. There's a common high-pressure line, as opposed to one per cylinder in the older system. But both systems use high-pressure lines to feed the injectors. It's just a matter of how many.

I'm not doubting that some, perhaps many, pre common rail diesels used the system as described in our article. I have heard of cam-driven injectors used on older diesels, all fed by a low pressure (common) fuel line. I've just never worked on one. I suspect that large marine engines may still work this way.

My experience, pre common rail, is limited to small marine engines, and a few diesel tractors, light trucks, and buses. But it concerns me that ALL of these have used the system I described. It's still in use, was once very common, and in some applications at least it still is. As the whole reason that common rail is called what it is, it should have at least a mention in the lede.

Am I missing something? If I'm right, then our current article is highly confusing and misleading... or in layman's terms, just plain wrong. Andrewa (talk) 19:04, 24 August 2016 (UTC)