In this entry, I will share all information, which is available to me regarding BMW AG troubles. Why I put an accent to “is available”? Because it is clear that each manufacturer tries to hide his problems. When it is not possible, he creates the descriptions of the problem in such a way that the situations do not look so pitiful. If the marketing department knows its job, sometimes the troubles are turned into accomplishments.

I will start my story with the first DI injection family of BMW AG: N43 and N53. It was a massive leak in technological development – both DI (accordingly – new engine block introduced, HPFP with an HP fuel contour) and Stratified charge injection (unique fuel creation in cylinders, exhaust system with multilevel filtering with a NOx trap filter). At this moment, piezo injectors appeared in the BMW petrol engine. And the story can begin.

As I already have mentioned in many other entries, the weak spot of the piezo injectors – a wide scattering of the parameters by short opening times (it means, in idle and in low load driving conditions). Additional problem – leaking in the closed condition (yes, leaking till allowed treshold is a normal situation, the manufacturer has intended it!). Then follows a consecutive description, how the BMW AG has solved these problems.

N43/N53. E series. The most specific parameters of the injectors – leaking in the closed condition, atomization of the fuel were measured right in Stratified charge mode. Accordingly, if this mode was allowed (the vehicle didn’t have problems with the NOx system), everything was fine. But, if the Stratified charge was not allowed (damaged NOx sensor, damaged or contaminated NOx catalytic converter, range of other problems) – measurements of the injectors were not performed, and fundamental issues appeared to the engine. Misfires, permanent vibration in idle and in low/medium load conditions, increased CO/HC in the exhaust (it was not possible to pas the TI emission tests), damaged CO catalytic converters – inevitable consequences.

N54. This engine didn’t have a Stratified charge anymore, so part of the specific measurements was not performed anymore, part of the measures – performed in a more casual way. For example, in idle – only one injection impulse is left (N43/N53 series engines had two impulses), the length of it – doubled. Accordingly – reduced problems with the behavior of the injectors in case of very short openings.
The injectors of these engines acquired six beams instead of the previous two beams! It provides better fulfillment of cylinders with the fuel. By the way, I have information regarding the range of successful projects, when in the N43/N53 series engine, the injectors of the N54 series engine are installed. The engines successfully run even in a Stratified charge! Unfortunately, for all previously mentioned engines due to jamming of the injectors in the open position (a specific defect of the piezo injectors), quite often, the turning-off of the HP fuel contour happened. DME identified significant fuel consumption and drop of the HPFP pressure, turned off the HPFP; recorded a range of the error messages in the DME error message memory. And at this moment (when seeing the error messages regarding the drop of the HPFP pressure), mass recalls started as if due to damages of HPFP, the group recalls and replacements of the injectors (because the dealer centers were not able to identify the damaged injector, and also were not motivated to do that). Due to injector problems, these engines were a nightmare for BMW AG.

N53. F series. Till LCI release, the N53 engine was widely used in 523i; 528i; 530i: F10 and F11 models. Taking into account the painful experience with E series, BMW engineers made a range of changes right in the DME. MSD80/81 was replaced by MSD87. What fundamental changes expected this generation of the engines? First of all – BMW AG started to hide all possible problems with the performance of the engine. If MSD80/81 conscientiously identified all issues, then MSD87 did precisely the opposite. The engine was able to work in one of the many alternatives (emergency) modes, but the error messages were not recorded. Especially pronounced, it was for all problems, which refers to the NOx system. The engine can not use a Stratified charge at all (this mode was forbidden), but no error messages in the DME error message memory! Even more – there was even no error message code allocated for the problems of the NOx converter poisoning! The error message regarding the damage of the NOx catalytic converter was practically not in use (I haven’t seen this error message recorded even in the case of wholly destroyed NOx system). To solve the problems, which appeared when the Stratified charge was not used:

a) the algorithms of maintaining the idle in Homogenous mode were reworked. Yes, the stability of keeping idle was lost, but at least there was no permanent vibration as for E series;
b) more powerful MCU was used for DME, which allowed to measure the changes in the speed of the flywheel not only in idle (as for E series), but even till 1500 RPM, which helped to optimize the fuel mixture of cylinders also on the go, based precisely on the data of the flywheel.

Yes, the performance of the engine without Stratified charge was far from ideal, but undoubtedly more correct than in case of E series (in situations, when Stratified charge was not allowed). Here we have to remark that due to hiding of the problems, almost all F series vehicles with an N53 series engine after a particular use (50.000 km+) were not using a Stratified charge. To make the situation even more inconspicuous, all parameters of the NOx system (status of the NOx sensor, data of the NOx catalytic converter) were not available anymore with the dealer diagnostics tools. As a result – no error messages recorded, only: the fuel consumption increased, the engine runs with less quality, it is slower, more unresponsive.
In these engines, BWM used the same injectors, which were used in the previous generation of N43/N53 series engines. For many years already, the actual (last) release of the injectors: 11.

N63. Also, these engines didn’t have a Stratified charge. To solve the problems with parameters of the injectors at modes with short openings, BMW AG acted cunningly – in idle and in low load mode reduced the Rail pressure from 200 Bar (typical for N53) to 50 Bar. There was no need for two injection impulses anymore. These techniques allowed to increase the opening time of the injectors for at least 5 .. 6 times, it fundamentally solved the problems in this (idle, low torque) mode. Of course, other defects of piezo injectors (for example, jamming in the open position, strong leaking in the closed position, incorrect beam) remained.
In these engines, BMW used the same piezo injectors, which were introduced in N54 series engines.

N55. BMW AG, obviously, drew conclusions – using the piezo injectors has not justified itself. Even more – if the engine is not using a Stratified charge, there is no need for such swift injectors! Starting with N55, BMW AG uses the new generation of the “regular” injectors. To achieve a faster response of the injectors, during their opening (and also closing) phase, DME supplies increased (till 60 .. 70V) voltage. Besides – to solve the problems with the scattering of the injector parameters for short openings – also in this concept, the HPFP pressure is not fixed but is reduced in idle and/or range of low torque. Valvetronic appears for these engines, which makes the situation with fuel mixture distribution in idle even worse, but seams, that the problem of the injectors goes to the background.

N20/N26. In N20, the same injectors as for N55 are used. Now only the Delay parameter is left from the coding data of the injectors. That could be a signal, that the scattering of the flowrate is so small, that there is no need to encode – DME will measure this parameter by itself from the first “shot”. Sounds good. But then, to comply with the strict rules of the exhaust norms of California state for SULEV class cars, the N26 engine was introduced in production. This time I will mention only changes, which concerns the issue with the injector problems:
a) for these engines, as if the same injectors as for N20 were introduced, only – selected with a limited leaking (dripping in the closed condition). Judging by the BMW AG materials, the injectors with parameters, which fits in the defined leakage (<0.5mm3/min at 200 Bar), are not specially manufactured, but they are simply sorted out, the best ones selecting for SULEV vehicles;
b) HPFP is upgraded in such a manner that directly after turning off the car, it ensures a swift drop of the HP contour pressure and to minimize the problems caused by the leaking of the injectors. Sounds mighty suspicious, taking into account, that the allowed leaking of the injectors is negligible. Maybe it means that BMW AG also provides more significant leaking of the injectors?
c) the generation of the DME software increased from MEVD 17.2.4 to 17.2.9. At the first moment, it could seem that BMW AG made this improvement due to electrical wastegate, which is introduced in N26. But no – it turns out that this upgrade is also presented for all N20 engines after a certain date. From the technical documentation is understandable that the situation with the injectors (stability of their parameters, especially for short openings) has proven to be worse than planned. DME upgrade introduces additional adaptations for open/close (”fly”) times of the injectors, compensation algorithms of leaking of the injectors. Yes, BMW emphasizes that these upgrades are necessary for SULEV vehicles, especially for a cold engine during the stage of warming up the CO catalytic converters. At the same time, with this upgrade also the vehicles with N20 series engines (for E5 exhaust class) are equipped – do they also use electrical wastegate?
Unexpected kindness from the manufacturer.

B48/B58. In these engines, the same injectors as for N55/N20/N26 are used. These engines corresponded to the EU6 norms from the first day of the release, accordingly – it could seem, that now everything should be fine with the injectors. But…

But the most interesting will only come!
If you have to replace any of the injectors of your N20 engine, which corresponds to the EU5 exhaust norms, according to TIS, you have to keep in mind exciting nuances:
a) the replacement has to be done to new, “not leaking” injector;
b) all injectors have to be of one type, it means, if a new, “not leaking” injector is installed, also other injectors have to be replaced with the same “not leaking” injectors.
BMW proudly calls it “EU5 to EU6 conversion procedure”.

Here, as for an example – the warning in case of the replacement of the injector for N55 engine:

Here, as an example – injector options for the vehicle, equipped with N20 series engine:

As you see, actually, two codes of the injectors are available: for EU5 and for EU6 requirements.
Both codes as active are also marked in BMW AG databases.
And since the end of the Year 2012 also the code of the new EU6 injectors has been changed:

As we see, ETK clearly indicates that the retrospective exchangeability is not allowed!

New nuances appear in BMW AG materials regarding B58 engine:

Here, the EU5 injector in the left, EU6 injector – on the right.
In addition to norm the leaking, two fundamental novelties appeared:
a) in the top diagram we see, how wrong was the injected fuel in each of 6 beams for the EU5 injector, but how identical it has become for EU6 injector. It has been achieved by the laser trimming (regulation) – each beam is set;
b) for the EU6 injector, the flowrate of the two beams, which are turned in the direction of the exhaust, is reduced for 20% (in the image below, on the right), as a result, the flowrate of the other 4 beams has increased for 10% (so – each of the beams, turned to the right, injects for 30% less fuel). Such a solution has as if improved the fulfillment of cylinders.

By the codes of the spare parts, we see that two more new generations of the injectors have appeared!
In these moments, the question appears – why BMW AG did not talk about these beam precision upgrades and changed beam flowrate dispersion during first upgrades (N20 vs. N26)? Obviously, these upgrades were not yet introduced at that time!

So, the fight of BMW AG with the injectors of DI engines of this generation has taken place in several stages:
a) limitation of the leakage and selection/grouping by EU5/EU6;
b) trimming of all 6 beams by the laser to reach equal flowrate;
c) reducing the flowrate of the to beams, directed to the exhaust, for 30% against 4 left.

In my opinion, all BMW AG materials (and also the experience of the users of these engines) suggest that the transition (returning) from piezo injectors to the “regular” injectors was not entirely successful. Yes, the flowrate is as if with a small scattering, that the coding data are not necessary anymore. Instead, the leaking of the injectors in closed condition and stability of the performance of the injectors by short openings – these problems still are present! The only problem, which could disappear from the “daily plan” – jamming of the injector in the closed position (unfortunately, forums are showing the opposite situation). The mechanism with the spring is more robust and “stronger.”

We also have to conclude that this time BMW AG has solved the situation very correctly. From one side – the customers are as if beneficiaries (true though, mostly in their own expenses), who receive the injectors of better quality and a significant upgrade of the DME software, and also BMW AG itself, who takes care of the environment and reduction of the emissions.

What would I do, if I had the engine, equipped with these injectors?
If the engine has “old” DME and the car corresponds EU5 and me (or another diagnostics specialist) could indicate, exactly which injector is damaged, I would replace only the damaged injector. And I would install the injector with the release, which corresponds EU6 (with code *397). After replacement, I would NOT upgrade DME to 17.2.9. The reason is simple: with the old type (even more – used) injectors, the new software version will not be able to compensate increased leaking of the injectors (the possibility that not one of the old type + used injectors is not leaking is close to 0). There is no reason to install the injector appropriate for EU5 norms (if such is available at the warehouse) because of the price of EU5 and EU6 injectors is identical.
Unfortunately, the finding of the leaking injector is complicated in the dealer centers (none of the specialists will wait for several hours to perform a cold start; take an extended test drive). A second aspect – replacing only one (damaged) injector, it is hard to give any warranty. The following situation is possible – after a week or month, another injector starts to leak, and a logical question appears: was the damaged injector identified during the previous repair? For these reasons, the dealer centers replace all injectors at one time.
Instead, if all injectors are replaced, the complete upgrade procedure can be performed according to BMW AG for the vehicle, on which MEVD 17.2.9 (after July 2012) is installed.