This entry is dedicated both to the owners of the cars and test performers, calling on them to evaluate the conclusions regarding test results of the injectors or any other components. Yes, the background of the findings, made in this entry, is based on an in-depth study of maths and physics during studies (it allowed to notice the discrepancies during several seconds). Still, all conclusions can also be made by the “regular” person, using logic and thinking a little.

In this current case, five injectors were unreasonably defected, causing unjustified expenses of around EUR 1500. We have to understand that it is for one customer. If this is a regular mistake, the costs of the error can reach a considerable amount of money. I deliberately use the word “error” because I have no reason to think that any of the parties involved are trying to cheat intentionally.

The story: the owner of the car with the N53 series engine approached one of the companies, which uses Carbon Zapp equipment for testing the injectors because suddenly problems with the engine performance appeared (the engine started to vibrate, EML symbol lighted up in KOMBI).


Here, the test results.

I will start with the injector No.2. This injector, as if has fundamental problems – it (not taking into account as if correct capacity) had not reacted to the given signal. Due to this reason, future tests are not performed, and the injector is marked as wholly damaged:

I have no reason not to believe the test performers, so let’s leave this injector “alone.”


Now the results of the tests of all other injectors follow (1st;3rd;4th;5th;6th):

Here, as we see – all injectors have not passed the tests successfully, and the verdict – they should be replaced. To prove it, the specialists of the company of the injector testing performed the repeated analysis (at the same time, at the same temperature and other conditions):

Here, the new injector has passed the tests successfully. Everything sounds logical?


Let’s check more further.

As we see, none of them as if damaged injectors do not leak in the closed condition. Tests NLT are successfully passed! Interesting nuances: ALL tests, not passed by the ALL damaged injectors (as a minimum: 2, but typically 3) indicate an increased amount of the injected fuel.

And now, let’s check the tests, successfully performed by the new injector.

In the last column, the delta between max allowed values and measured data calculated.

The difference for both TP1 and TP4 tests data and max values is only 0.3mg! There is no slightest doubt that the test results are very close to the max allowed values. This difference can be compared by measuring error. No illusions – when performing the repeated tests, some of them definitely could reach above the max value – also, the new injector will have the same problems as the used ones. At this moment, I got a bit suspicious. I assume that to get such a successful result, the test was done for several times. And that actually is not entirely correct. But – it is only an assumption, and I have no evidence, unfortunately.

Also, the test results of TP2 and TP3 are significantly close exactly to the max allowed values.

Let’s go back to them as if damaged injectors. You can see the data by yourself – as if unsuccessfully passed tests actually overreach the max values for typically 5 .. 10%. Is it a lot or a small thing?

At this moment, some basic data should be marked:

initial (factory measured) parameters of new injectors, used for N43/N53 engines, can differ:

  • delay: +/-42% (1.55 .. 2.86 mg/stk);
  • flow-rate: +/-17% (52.9 .. 70.8 mJ).

The allowed (and true – for used injectors) scattering is even more extensive.

In injection modes, which are typical for low/medium load (for example, TP4 test) – even not performing particular calculations, it’s clear – even for new injectors, the injected fuel amount can differ even for +/-25 .. 35%. Conclusion – Carbon Zapp provides significantly narrowed corridors of the allowed values than the manufacturer has intended for new injectors. Moreover – injectors coding data is not included in calculations!


So, we have to take into account these nuances:

  • Carbon Zapp equipment does not measure the parameters of the injectors in the conditions, defined by the manufacturer (in which the Delay and Flowrate is measured);
  • the allowed test corridors of the Carbon Zapp equipment do not correspond the allowed tolerances, defined by the manufacturer (they are more narrow); coding data is not included in calculations at all;
  • the test results are affected by the machine itself (physical characteristics of the liquid, an indication of the pressure sensor and weight indications and their precision).


One more significant argument: TP3 test is as if intended to the injection mode of the emission test (idle/2000 RPM, 0 loads, CO/HC test mode) mode. Pay attention to the test conditions:

  • pressure: 65 Bar;
  • impulse length: 650 us.

These data correspond to the N54/N55/N63 series engines! The N43/N53 series engines have RADICALLY different work conditions in these injection modes!

For N43/N53 series engines:

  • pressure 150 .. 200/200 Bar (N43/N53);
  • two impulses (not one as for N54/N55/N63);
  • impulse length – radically shorter (around 200 .. 250us).

Here, one more evidence that also this (Carbon Zapp is the most potent test equipment at this moment) can not be blindly trusted!

What are the reasons that al test results seem as “shifted” to larger values? Possibly – use of liquid with slightly different compositions. Probably, the pressure sensor is slightly “lying”. Perhaps, the weights are somewhat “lying”. The various technical solutions of the injector driver systems (different dU/dt, different Umax) – also, this obstacle will have a significant impact on the test results.


My verdict: ALL as if not passed tests actually are passed successfully. That, if any of injectors has problems, has to be checked in real conditions (temperature, Rail pressure), using diagnostics equipment (INPA).


In this case, customer unjustified spent around EUR 1500. I call on Carbon Zapp specialists:

  • upgrade the test profiles according to the N43/N53 specifics;
  • implement correct (according to the manufacturer’s details) corridors of min/max values;
  • implement adaptive corridors, appropriately the delay of the injector and flowrate encodings;
  • train the staff in using the equipment and interpret the data.

Such mass errors are not acceptable! They are too costly to the customers!


Here, INPA data regarding the “health” of these injectors both in Stratified and Homogeneous mode:

Not the slightest problems! Also, live data of the injectors, Fuel mixture, and Rough run data confirm – everything is in the best order with these injectors!

Here, with these “damaged” injectors, the engine perfectly performs even in Stratified charge – in the most sensitive injection mode!