Why code the injectors?
Modern diesel injection systems designed according to the principles of common fuel accumulator - “fuel ramp/rail/rail” (Common Rail - common ramp), have undeniable advantages in relation to engines with mechanical injection. The advantages, undoubtedly, include such points as higher efficiency, uniformity of fuel combustion (as a consequence, uniformity and quietness of engine operation) and environmental friendliness up to EURO-7.
Such virtues have been made available by:
А. Extremely high fuel pressure in the main line (up to 3000 bar in the most modern variations);
B. Optimization of the atomization torch and the injection cycle. The injection cycle is (functionally) divided into three main stages:
1. Pre-injection
2. Main injection
3. Subsequent injection.
Details of the purpose of each can be found in the table below.
| No. | Stage Name | Purpose |
|---|---|---|
| 1 | Preliminary Injection | Preparatory stage and heating of the combustion chamber |
| 2 | Main Injection | Key fuel dose required for piston movement |
| 3 | Post Injection | A small fuel dose (approximately equal to the preliminary injection) to normalize the end of the combustion process and suppress excessive engine detonation |
The data given in the table reflect the injector speed only approximately. In real fuel systems there can be several pre-injections, subsequent injections. On the most technologically advanced variations of fuel systems it is currently possible to count up to 9 injections per injector cycle (Deplhi DFI-3 systems).
This phenomenal performance is managed by the ECU (in repair specialists' slang - “brains”). It receives information from a multitude of sensors - mass air flow sensor, intake manifold pressure sensor, fuel pressure sensor, engine shaft position sensors, detonation sensors and many others). Based on these signals, a conclusion is made about the current mode of operation of the engine, its load, as well as the status of all auxiliary peripherals of assemblies and units.
The fuel injector must have perfect electro-hydraulic balance in order to respond adequately to the control unit's commands. In the course of daily operation, deviations occur in one way or another due to natural wear of the injector components, as well as various kinds of damage caused by poor quality of the fuel used and insufficient filtration. We will leave the damages and methods of their elimination “overboard” of this article. Let us focus on natural wear.
To compensate for it, there is a mechanism in the operation of the engine control unit - long-term correction. When it is implemented, the ECU records the actual participation of each cylinder in the total rotation according to the detonation sensors and crankshaft sensor and makes appropriate changes in the parameter “injection time” for each injector. The long-term correction process is gradual and time-consuming. When very large corrective adjustments are required to stabilize the engine (outside the range provided by the manufacturer), the engine control unit will detect an error in the functioning of the problem injector and warn the owner of the problem by activating the Check Engine indication. The further action of the car owner in this case will be a visit to a car service center for repair or replacement of the injector.
Now a few words about inaccuracies during injector assembly. It is quite difficult to avoid them and, in factory conditions, also economically inefficient. Paying more attention to each manufactured injector than is stipulated by the production flow chart means losing money. Therefore, one way or another, one produced injector will differ from the neighboring injector. To compensate for these differences, another mechanism was developed and implemented - short-term correction (also called “coding”). The essence of this mechanism consists in obtaining actual hydraulic parameters of the injector (bench test), analyzing the obtained values, comparing them with similar parameters of an ideal, reference injector and assigning a correction code.
The code is an alphanumeric designation formed by a special algorithm, which reflects the difference between the actual performance of the tested injector and the reference. This code is stored in the engine control unit memory. From the moment the code is entered, the ECU firmware “sees” what corrections need to be made when working with a particular injector. This correction mechanism starts working immediately when the code is entered into the ECU memory, that is why it is called “short-term correction”.
In the presence of minor deviations in the operation of the injector after repair, theoretically, it is possible to exclude coding from the mandatory procedures, while giving the stabilization of engine operation to the long-term correction mechanism.
While adaptation is taking place, the car engine makes unpleasant sounds, runs unevenly, and smokes heavily. Why should not ignore coding when repairing fuel injectors? Here are three simple answers to this question
First, the procedure for starting an engine on injectors without a code is incorrect in the extreme, and the procedure itself can put the engine out of commission.
Secondly, quite often it is not possible to adapt injectors without a code. You waste time on repeated disassembly, diagnostics, adjustment or give the customer an incomplete job.
Thirdly, even if the engine operation has stabilized, you have normalized it due to the correction range of the long-term correction mechanism, going beyond which, as we have already mentioned, activates Check Engine. The customer will be extremely dissatisfied if this happens in a short period of time after the repair.
To summarize. Fuel injector coding is a mandatory step in its repair. By coding injectors, we make adjustments, perfectly balancing the hydraulic parameters of the electromagnetic injector, and in the case of Piezo Bosch also the electrical parameters.
Injector testing equipment from Diesel Easy, such as the BlueBench or Modern test benches, allows you to check and assign correction codes:
— for Bosch electromagnetic and piezoelectric injectors (IMA/ISA);
— for Delphi Euro3/4/5 (C2I, C3I) solenoid injectors;
— for Denso solenoid injectors (QR);
— for Siemens (IIC) piezoelectric injectors;
The coding algorithms of the above mentioned manufacturers' injectors fully correspond to the original ones. The coding procedure on BlueBench and Modern is quite simple and automatic. The development of manufacturers in modernization of coding technology is promptly monitored.
All innovations are added to the capabilities of the Diesel Easy stands to give you consistent and high quality results.
Why code the injectors?
Modern diesel injection systems designed according to the principles of common fuel accumulator - “fuel ramp/rail/rail” (Common Rail - common ramp), have undeniable advantages in relation to engines with mechanical injection. The advantages, undoubtedly, include such points as higher efficiency, uniformity of fuel combustion (as a consequence, uniformity and quietness of engine operation) and environmental friendliness up to EURO-7.
Such virtues have been made available by:
А. Extremely high fuel pressure in the main line (up to 3000 bar in the most modern variations);
B. Optimization of the atomization torch and the injection cycle. The injection cycle is (functionally) divided into three main stages:
1. Pre-injection
2. Main injection
3. Subsequent injection.
Details of the purpose of each can be found in the table below.
No.: 1
Stage Name: Preliminary Injection
Purpose: Preparatory stage and preheating of the combustion chamber
No.: 2
Stage Name: Main Injection
Purpose: Key fuel dose required for piston movement
No.: 3
Stage Name: Post Injection
Purpose: A small fuel dose (approximately equal to the preliminary injection) to normalize the end of the combustion process and suppress excessive engine detonation
