Several years ago, I wrote an entry regarding our local company, which has bought a piezo injector cleaning module for their injector cleaning stand. I was the first customer who tested the equipment and 10 different injectors (correctly performing or with well-known defects).
After the test injectors were cleaned, and for some, the identified leaking disappeared when tested repeatedly. The first experience was not excellent, but I didn’t have any significant expectations (the reasons are mentioned below).
After several years I decided to write a second part for that entry because I have collected data and experience for many customers (several hundred at least) from different European countries.
Unfortunately, conclusions are pretty harsh.
First – only in rare cases, diagnostics indicate some problems. Why?
a. tests are performed at room temperature. Leaking if the piezo injectors often manifest in low temperatures – these defects can not be identified at room temperature. Precisely the same situation, if the injector leaks exactly/only in high temperatures (work temperature of the injector reaches 100+oC);
b. for example, the test pressure of the ASNU complex is 5 bar, but the Rail pressure of N43/N53/N54/N63 engines reaches 200 bar. It is clear that the 40 times lower test pressure will not indicate any problems with the injectors. Only totally worn injectors will leak under these conditions. In conditions of 5 bar pressure, the true flowrate, shape of the atomization also can not be evaluated;
c. for more advanced and widely available Carbon Zapp test complexes, the N54 engines injection profiles are used to test these piezo injectors. These profiles are completely different from N43/N53 series engines (one of the aspects – 50 bar pressure in idle for N54 series versus 100 .. 150 .. 200 bar for N43/N53 series). Carbon Zapp does not evaluate the flow rate of the injectors in short opening modes (100 .. 200 us impulses). Strictly, these modes are used in most critical conditions: idle and deficient torque mode. In addition, for shorter impulses modes (Carbon Zapp offers 240 us impulse test), lower test pressure (180 bar, not 200 bar) is used, which also does not correspond to the proper conditions:
d. none of the stands does intend an exact measurement of the angle of the injected beam. The DI method, used by BMW (and only BMW), ignites the fuel at the moment of its injection, which means the fuel shout “hit” right next to the spark. It will not be ignited if the fuel is even a little further from the spark plug. Also, if/when the fuel hits the spark plug and “floods” it, misfire is guaranteed. Unfortunately, none of the stands doesn’t even detect this range;
e. primary performance mode of N43 and N53 series engines is Stratified charge, which means – the fuel is ignited directly after injection. Fuel has 0 times to mix with air in the combustion chamber. In this mode, atomization of the injected fuel is very important. Atomization is defined by the “character” of the fuel – it is injected in micro drops (tiny fog) or in a stream. Unfortunately, the evaluation of atomization quality can be evaluated only visually. It is clear that visual inspection is unreal for short injector openings (ten thousand parts of the second long): the human vision has much larger “inertia”. Unfortunately, none of the stands is equipped with a very high-speed performance (hundreds of thousands of images in second) camera, and it has to be understood that such a camera costs huge money;
f. finally – most often, sporadic defects are typical for the piezo injectors (at least in 50% of cases). It means imperfections, appearing and disappearing, and even a perfect stand will not indicate such a defect.
One more fundamental problem – cleaning fluid and cleanliness of the whole system. Opening of the piezo injector for the leakage (max allowed) is a few parts of the micrometer. Each most minor dirt, impurity, the foreign body causes enormous problems. If used injectors are placed in the stand (and exactly such ones are – used, clogged, leaking, etc.), the dirt from them gets in the cleaning system, from cleaning system – it can get back in the following injectors, which will be put for testing. It is clear that the cleaning liquid is not replaced after each injector, and it would be an inadequate cost. I addition, all system is contaminated – pipes, storage container, etc. This is a fundamental problem of cleaning and testing these capricious injectors.
In addition to the previously mentioned arguments, we have to conclude that most users of these stands don’t even know how to properly use them! At least in 50% of cases, the reference data of the injectors were input incorrectly (for example, with a vast allowed range); as a result – even damaged injectors “successfully” passed all tests! Practically in none of the cases, the service staff has not made any conclusions themselves, hadn’t given any additional information (even in instances where completely unsatisfactory test results were output).
In many cases, the performance of the injectors got much worse after cleaning; a pronounced flow of the injector in a closed position was observed. At least one of three cases of such injector cleaning resulted in replacing all injectors because their leaking after such tests has become a catastrophe. Obviously, the cleaning liquid was contaminated by impurities, which got stuck in the injector’s nozzle.
Unfortunately, in none of the (many) cases sent to me, I could not confirm NOT EVEN ONE of the laboratory test results would at least approximately correlate with the measurements of DME itself in actual work conditions. Yes, the situation is precisely so harsh.
Note: for N43/N53 series engines, INPA allows to evaluate following parameters of the injectors (measured by the DME in the actual work conditions):
a. injector flowrate measurements in Homogeneous mode (results of chemical tests) in different segments; also for cold engine;
b. injector flowrate corrections (atomization quality also is detected separately) in Stratified charge (results of chemical tests);
c. leaking of the injector in a closed position in Stratified charge (results of tests of mechanical efficiency);
d. corrections of the Delay parameter of the injector both in Homogenous and Stratified charge modes (results of tests of mechanical efficiency);
e. mechanical efficiency of each cylinder in idle both in Homogenous and Stratified charge modes;
f. delay and flowrate correction data applied to each injector in the current moment;
g. set of electric parameters of each injector – charge/discharge energy; reached voltage at the opening period;
h. error message recording with thorough freeze-frame data: in which conditions and what kind of problem the injector has experienced;
i. misfire density data (available OBD Mode 6), which allows evaluating (also) the beam of the injector.
Several tenths of different parameters are available regarding each of the injectors and live data, which indicate the performance of each injector (cylinder) in the exact performance modes.
Summary of this entry – I categorically DO NOT recommend cleaning these injectors, and I also DO NOT recommend testing these injectors. Not even talking about the waste of money, your injectors will get contaminated with the impurities from the test contour. My suggestion – keep away from these stands!
What to do?
a. perform professional diagnostics, during which the data of all injectors are analyzed;
b. replace the injectors, which were indicated as faulty during diagnostics;
c. perform the necessary service procedures (encoding of the injectors, re-adaptation of the engine);
d. evaluate the situation after repair.
Note: for N43/N53 series engine, the full functionality – Stratified charge – should be restored first. Reason – many parameters of the injectors are measured precisely in Stratified charge mode.
Also read: fuel additives. Want to try?