In this entry – about the testing of the injectors.
Introduction: some of my reflections/conclusions.
No matter how “powerful” the testing equipment is, it will not be able to repeat the “real-life” conditions. Usually, the problems persist either in low (below 0 oC) or in high temperatures (above 100 oC). Sometimes the defect is sporadic – it can “disappear” exactly at the moment of testing. Accordingly – unfortunately, even using perfect equipment, there will be situations, when the hidden defect will not be indicated.
Wery important is also a person, who performs the diagnostic – diagnostics specialist. The shape of the fuel bundle is observed exactly by the diagnostics specialist. The amount of injected fuel is measured exactly by him. Exactly he is the one, who will notice some peculiarity or strange “behavior” of the injector. Or directly opposite – will not notice.
A second part, which is directly depending on the diagnostics specialist – in what technical order the diagnostics equipment and in how to clean environment the testing and cleaning liquids are kept. I have experienced a situation when after the cleaning of the injectors, the one, who were previously working perfectly, started to leak. How such a “result” can be reached? Clean countless injectors in the same liquid – because so you can spare some money.
The diagnostics specialist has to understand, exactly which test is intended for which purpose. I had witnessed a situation when the specialist works with the most powerful ASNU diagnostics stand, but he has no clue, what test is offered by each of 17 presets. And we are not even talking about that – this current specialist would know, what amount of fuel should be injected by the injector. Accordingly – zero sense of all test algorithms! Zero sense of expensive equipment!
Third part – it refers both to diagnostics equipment, diagnostics specialist and also the complete business culture of the company. This part is the paperwork, or – more exactly – fulfilling of exact data regarding each injector, each customer and issuing of a technical report.
Yes, I have seen a “diagnostics”, which manifests as following: the specialist from the adjoining room brings a handful of injectors. In one hand he keeps the injectors, which “as if” are good, on the other hand – ones, which “as if” are damaged. Of course, the injectors are not numbered, their defects are not registered. There is no confidence, that the injectors are the ones, which were brought by the customer.
Yes, of course, it is much easier if the test equipment itself insures a template of the test protocol (or even fulfills the protocol by itself), but – even if the testing equipment doesn’t offer an automated creation of the protocols, the specialist can create one by himself – not a bit worse than the automated one!
Some time ago, I had a chance to see an ANSU test stand, which was equipped with ad additional module for testing the Piezo injectors of the petrol engines. I had one fundamental objection: the test pressure was only 5 Bar! It’s by safety reasons, as claimed by the diagnostics specialist (and manufacturer). Partly – understandable. But – there are anyway stands for testing the injectors of diesel engines with pressure till 2000 Bar and even more! Unfortunately, due to this pressure limitation, ASNU is quite inefficient.
A much better situation is with Carbon Zpp test stands. Advantages of these stands:
a) test pressure till 850 Bar;
b) check-up of the electrical parameters of the injectors;
c) injectors tests with known amounts of injection;
d) creation of automated reports.
One of my customers sent me a Carbin Zapp diagnostics protocol:
and here: test data of each injector:
As you see:
a) at first, the “health” of the element injector is checked. The capacity of the elements of injectors is measured, but, what is much more important – min/max values are indicated. As if small thing, but – each test has a name! It’s enough to mention: R2LC test passed – and for everyone, which works in the industry, it’s clear which test procedure exactly is mentioned;
b) in NLT test, the leaking in the injector is tested. And what is more important – test pressure 205 Bar! And that exactly what the test pressure should be! In several entries I have mentioned – the injector was leaking, but the leaking disappeared, when the Rail pressure dropped to 180 .. 190 Bar. So – a lower test pressure won’t be OK, not even talking about 5 Bar pressure of the ASNU!
c) iVM TP1 test: test flow-rate of the injector. The opening time of the injector: 1050us = 1.05 milliseconds. Very important – min/max values are indicated. Obviously, the test developers have mathematically calculated the allowed flowrate corridor (knowing the min/max values of the injector encoding);
d) TP2 .. TP4 – additional tests with different pressures, with different length of the pulse. Yes, if I would have a chance, I would additionally use also 220 .. 250 Bar pressure, because my experience shows – exactly in conditions of increased pressure, the injectors start to leak. A second nuance, which I would include in the tests – packs of very short impulses (min opening time: 100us). Exactly such a test would indicate a”post” reaction of the injector to the impulse, the shape of the beam emitted in a half-open position.
Why this picture is so important?
Each injector is numbered. Regarding each injector, there is a note, in which cylinder it was located before the test, in which cylinder it is placed after the test. If the injector is rejected (as in this example), an appropriate remark is done.
Why it is so important?
The higher the qualification od the performer of diagnostics, the more important is the information, gathered in such diagnostics. If I see any abnormalities in the performance of the injectors while performing the diagnostics, for me it’s very important to make sure, that the problem is solved after cleaning of the injector. Just as important – make sure, that no new problems have appeared in other cylinders. And, what is not less important – get a confirmation, that the injectors, rejected in the diagnostics, are also rejected in the tests.
If such information is not available, the following situation could appear quite easily: during diagnostics before cleaning, the injectors of cylinders No.1 and No.4 are rejected, during cleaning the injector 1 and 2 are rejected (but, as there is no information, in which cylinders these injectors were installed, there is no confirmation, that these are the same injectors, which were rejected in diagnostics), after cleaning the performance of cylinder No.5 becomes suspicious (but we don’t have information, if the cleaning of any of previously rejected injectors was not successful or any of other injectors got “damaged”). Accordingly – without this info: something was diagnosed as damaged, something really was damaged, after a repair, the situation has changed, but… There is no clarity! Even more – if after some time any of injectors will start to leam more strongly, it won’t be possible to make any conclusions, if any of the previously rejected injectors has started to leak again (and no options – it has to be replaced) or some other injector, which was previously working correctly, is now damaged (and it is worth to clean it).
In the existing example, the cleaning of the injectors has been done close to the perfect scenario. I give 9 from 10! It is really a pleasure to see professional work!
P.S. pay attention, how wide dispersion of parameters is allowed in TP4 test. 6.4 .. 12.2 ml, it means – the injected amount can differ for even 2 times! 240us corresponds to idle for warmed-up engine; 180 Bar – average value between N43 (150 Bar) and N53 (200 Bar) engines. Here, why for the engine, which is equipped with Piezo injectors, measuring of all injectors and correctly applied adaptations are so important – without it, the fuel mixture distribution between cylinders will be very incorrect, because by short openings the dispersion of injectors parameters are huge!