Today, an owner of E71 X6M turned to the workshop.
Several days ago, the owner of the car wanted to purchase injectors. BMW dealer asked EUR 3500 for 8 injectors, which sounded too much. Yes, the approximate price of an injector is around EUR 200 (of course, we talk about OEM injectors).
It turned out the customer has performed a diagnostics in this dealer center, where it was said to him, that 4 injectors are damaged, and all injectors have to be replaced due to this cause. And after also both HPFP have to be replaced.
The customer has a calculation for the first stage – for replacement of the injectors.
It’s not hard to calculate the total costs of the repair – they will reach at least EUR 6000.
Why I don’t call the name of the dealer center? I have no reason to doubt any word from the owner of the car. The problem is an obstacle, that the dealer didn’t give to the customer any protocol of diagnostics; in case of dispute/litigation (for defamation) the employees of the dealer center can “turn on the reverse”.
Note. In my presence, the owner of the car called the dealer center and tried to get the protocol of diagnostics, where these defects (damaged injectors and HPFP) are fixed. Unfortunately – without any success, because the papers have “went upstairs”, after several weeks they will “come back downstairs”. In any case – they are not available (yet) anymore.
Symptoms of the problem – close to max RPM, in exact conditions, the engine loses power/torque for a moment.
When did I hear about the symptom, my first question – why the injectors were blamed at all? If the engine has a good torque in the range of average RPM, what suddenly happened in increased RPM?
The opening times of injectors don’t even change!
The argument/assumption “it’s not enough time to inject” – something like that can be said only by a person, which don’t understand anything from basic performance thing of the engine. In N63/S63 series engines, the piezo injectors are used, their opening times are 5 .. 10 times shorter than for “regular” injectors. Accordingly – even, if the rail pressure would drop at least 10 times, the opening times of injectors won’t be longer than for engine of the previous generation (and that thought has enough time reserve). In addition – it’s not possible, that DME wouldn’t notice such (not one time) drop of pressure/injected amount! In additions – several (or maybe – all) injectors suddenly have some unheard, sudden, and not even theoretically possible defect? Sound’s like a nightmare!
So, the customer was convinced to perform one more diagnostics, this time in the workshop, before an investment of a significant amount of money.
First stage: identifying the situation.
Error messages – not present. History list: passive error messages regarding several misfires – nothing interesting.
Fuel mixture data:
Fuel mixture (Lambda, voltage) – correct; wideband probes trimmed correctly; control probes – voltage correct, no misfires observed; multiplicative type adaptations – correct ( in range of 5 .. 6 %).
Offset type adaptations of injectors:
Very correct, no slightest signs, that any of injectors would leak.
Rough run data:
Mechanical efficiency – in range of several %, in addition – bar regularly changes “polarity”, it means, DME has managed to completely compensate differences of cylinders.
Data of each injector are checked:
activation voltage and charge of each injector, opening time. Opening times in different modes/map sectors are compared (applied individual adaptations, which are made, based on tests of chemical and mechanical efficiency). All data – perfect. No slightest signs, that any of injectors would be “tired”. Their piezo elements are without defects.
Knock sensors data of cylinders?
Very similar. No slightest sign, that any would have problems with burnout, increased/reduced amount of injected fuel, detonation.
Maybe a problem with HPFP or LPFP?
The pressure of low-pressure contour – stable in each performance mode, deviation around 1 % – excellent result! The pressure of HPFP pump – identical, stable, deviation around +/-1.5 %, is maintained according to maps. Not even a sign, that there would be any problems!
Parameters as from a book.
Of course, parameters of injectors, pumps, the performance of turbines were observed in driving session, in real driving conditions by different required torque and RPM (not in idle). Nothing even suspicious!
Reference values correct, required positions correspond with real ones, jittering – in range of one “step”. Perfect!
The fuel mixture was observed in the moment of acceleration – it stayed correct. So – the engine has no fundamental problems nor with a fuel (fuel pumping and filter, LPFP and HPFP), nor with air (air filter, turbines).
Further, the max acceleration mode was repeated in mode Sport + mode “from a spot”.
At the same time, openings of the throttle valves were observed:
Opened throttle corresponds to around 81 deg. At the beginning of run-up everything was in order, but then, suddenly, the throttle opening for both banks was reduced to 45 .. 50 deg.
First conclusion – DSC system is triggered.
Here we have to take into account the following nuances:
a) studded tires are installed on the car;
b) stage 1 chip tuning has been performed for the engine, its torque curve is not “even” anymore, but it has maximums, which promotes the “get off” of the car in exact RPM conditions.
Note: DSC of this generation uses both data of accelerometer and wheel speed sensors. DSC will be activated even at the moment, when/if all 4 wheels of car spin.
The second loss of torque was immediately following the first one. Openings of throttles dropped to 15 .. 20 deg. In this case, the engine has reached redline and swiftly reduced required torque, to “spare” the engine. The owner of the car was not informed, that in this driving mode the car doesn’t switch next gear automatically if the pilot misses the right moment. The engine is so powerful, to change the gear from 1-st to 2-nd in the right moment – a quite complicated task. A moment too quick – RPM of the engine is far from the optimal moment, a moment too late – redline already.
In this time, the only real problem of the car – howling bearing, which was not noticed by the dealer’s mechanic in kindly offered diagnostics of the rolling part. And – completely inadequate engine diagnostics and estimate.
Note: none of the BMW documents don’t suggest to change all injectors if only some of them are damaged. True thou, as we see, even in case of perfectly working injectors, half of them can be “rejected”, another half – require to replace, based on non-existing BMW regulations. And with one effort – “catch” also both HPFP with a value of several thousand EUR…