Difference between conventional injection and common rail
Conventional injection, common rail or unit injector? What is the difference, as well as the advantages and disadvantages of each of the systems. For a complete architecture of the injection circuit, see here.
Classic injection
In the case of standard injection, an injection pump is directly connected to each of the injectors. This pump will then deliver pressurized fuel to each of them. The computer then checks the injectors to open them at the right time. It has the advantage of being robust enough due to its relative simplicity. Unfortunately, this makes the diesel brighter and noisier due to the rather simplified combustion process (we send fuel to the 3rd engine stroke and that's it).
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Common Rail Injection System
This time, there is a common line between the injection pump and the injectors (in some cases in the form of a sphere). This pressurized fuel accumulator provides higher and more uniform injection pressure across all injectors. This overpressure then ensures better fuel distribution in the cylinders, that is, a better air-fuel mixture.
In addition, the engines are a little quieter because it allows for fuel pre-injection. Indeed, engineers have noticed that the engine rumbles less if we do a tiny injection of fuel before the 3rd stroke of a 4-stroke engine (some even do up to 8 injections per cycle!), The one where the fuel is injected. an explosion (or rather, a fire... "Geeks"-mechanics are very careful in their use of precise terms!).
In addition, with this system, engineers can offer motors that use less energy and perform better at the same displacement.
There was no high pressure on older machines. Thus, there was a low pressure fuel / booster pump that directed fuel directly to the rail.
Modern cars need more pressure for direct injection, so there is a high pressure pump and the rail can generate much more pressure.
Pump nozzle?
There is a third method, which has been much less common and has disappeared since ... This unit injector system, invented and used by the Volkswagen group for many years, consists of installing a small, independent pump on each injector. This is instead of a central pump. One of the advantages was the ability to inject at high pressure, which was more important than conventional injection. Unfortunately, the power was coming in too quickly, which somewhat impaired the engine enjoyment aspect.
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Dernier comment posted:
Jerome (Date: 2021, 04:24:05)
Why did we replace the common rail pump in the new system.
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