Modern diesel injection systems, designed using the mutual fuel grid principle - a fuel rail, has a number of serious advantages over the mechanical injection engines. These advantages of course includes a higher efficiency, a more uniform fuel combustion (and more uniform and quiet engine operation as a result) and enviromental friendliness up to EURO-7 level.
Such benefits have become avaliable thanks to:
А. Extremely high fuel pressure in the line (up to 3000 bar in the most modern versions);
Б. Optimization of the flare pattern and injection cycle. Optionally the injection cycle is divided into three main stages:
2. Main injection
3. Subsequent injection.
More information about them can be found in the table below.
|1.||Pre-injection||Preparation and heating of the combustion chamber|
|2.||Main injection||Main fuel injection which is required for initial piston movement|
|3.||Subsequent injection||A small dose of fuel (roughly equal to the pre-injection) for normalization of the combustion process and extinguishing of excessive detonation.|
The data given in the table only aproximietly reflects the speed of the injector. On operational fuel systems there can be multiple pre-injections and subsequent injections. On the most advanced versions of fuel systems the working cycle of the injector can include up to 9 injections (the Deplhi DFI-3 system).
The managment of such an phenominal speed is taken over by the electronic engine control unit ECU. It recieves the data from a number of sensors: mass air flow sensor, intake manifold pressure sensor, fuel pressure sensor, engine shaft position sensors, knock sensors and many others. Based on this data the ECU makes a conclusion about the engine working order, its load, as well as the condition of all the auxiliary components and assemblies.
In order to adequately respond to the comands of the control unit the fuel injector must be in perfect electro-hydralic balance. In the course every day operation inevitably deviation arise due to natural wearing out of the injector components, as well as various damage caused by low fuel quality and insufficient filtration rate. But let us not talk about such damage and it repair in this article. Here we'll talk about the natural wear.
To compensate for it the ECU have a special mechanism - the long-term correction. The mechanism allows ECU to detect actual participation of each piston in the rotation of the shaft by processing the data from knock and engine shaft position sensors and makes corresponding changes and the "injection time" parameter of each injector. The process of long-term correction is gradual and time-consuming. When to stabilize the engine operation large corrections are requaired (outside of the range provided by manufacturer) the ECU will detect the error as the injector faliure and let the owner know by activating the Check Engine indicator. In this case the next action of the car owner would be a visit to car service to repair or replace the injector.
Now a couple of words about inaccuracies in the injector assembly. Such inaccuracies are hard and economically inefficient to avoid if we speaking about factory assembly. Paying to each injector more attenchion than provided by the production flow chart is merely a loss of money. So anyway each individual injector would more or less differ from the other. To compensate for these differences another mechanism was developed - the short-term correction (also called the "coding"). This solution collects the data about actual hydralic parameteres of the injector (bench testing), analyses them, compares it to the same parameteres of the ideal standart injector and assign to them the correction code.
The code is an alphanumeric designation generated according to a special algorithm, which reflects the difference between the actual data and the standart. The code saves in the ECU memory. From the moment the code is written inside it the control unit can "see" which adjustments required for each individual injector. This mechanism starts to work instantly after the code is written the ECU memory, this is why it's called the "short-term correction".
If a minor deviations of the injector appeared after repair, theoretically, it is possible not to use the coding procedure and stabilize the engine only by the means of the long-term correction mechanism.
When the adaptation process is running the car's engine can produce unpleasant noize, work unevenly and smoking a lot. Why you don't want to forget about the injectors coding? Let us show you three simple answers to the question.
First off, the engine starting procedure without coding is highly incorrect and can itself take the engine out of order.
Secondly, you can't adapt your injectors often enough without coding. You will waste your time on disassembly, diagnosis, regulations or will give your client an unfinished work.
And finally, even if the engine operation stabilized, without the use of the short-term correction, you can only normalize it inside the range of the long-term correction mechanism, which, as we said before, will activate the Check Engine indicator. The client would hardly be pleased if this indicator will appear in a short period of time after the repair.
Let us summarize. Coding of a fuel injector - is a mandatory step in injector repairs. By coding the injector you make a correction, perfectly balancing hydralic parametres of the electromagnetic injector, as well as the piezoelectric injector in case of the Piezo Bosch.
The testing equipment for injectors testing by Diesel Easy, for example the BlueBench or Modern test benches, allows you to set correction codes:
- for electromagnetic and piezoelectric Bosch injectors (IMA / ISA);
- for electromagnetic injectors Delphi Euro3/4/5 (C2I, C3I)
- for Denso electromagnetic injectors (QR)
- for Siemens piezoelectric injectors (IIC)
The algorythm of injectors coding of above mentioned manufactorers is exactly the same as the original ones. The coding procedure on BlueBench and Modern test benches is easy enough and kakes place in an automated mode. The development of manufacturers in matters of coding technology modernization is closely monitored by our specialists. All innovations are added to the capabilities of Diesel Easy test benches to make sure you will achieve a stable and high-quality result.