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How to check the Stratified charge for BMW F10/11

Testing of the performance modes of N53B30 for F10/F11 has certain specifics. The reason is the obstacle, that BMW has maximally hidden problems with the performance of the NOx system, locked the access to all typed of basic data which would allow identifying these problems directly or indirectly.

Part of the NOx system problems are not recorded in the DME error message memory at all (there are not even the error message codes intended), part – should be recorded (the error message codes are intended), but in practice – they are not recorded. It means – an empty error message list doesn’t mean that everything is OK.

What are the symptoms, that something is wrong with the Stratified charge (the main performance mode of the engine)?

At first – the fuel consumption increases. For 15 .. 25%. But there also are some nuances. If you have purchased a used car, it can not be using a Stratified charge since the day of the purchase. You will believe, that fuel consumption is normal. You will not know, that actually you are overpaying for the fuel. Also in case, if initially, something was fine, DME can gradually (and so it usually happens) turn off the Stratified charge. Fuel consumption increases slowly and seamlessly during the time of several months.

Second – the engine has lost the typical “easiness” of the performance. But also the recognition of this symptom is individual. There are many, who say – this easy, “flying” performance of this engine, the excellent responsiveness to the accelerator pedal can not be confused with any other engine. At the same time, some people oppose – well, this car drives, other car drives, what’s the difference? But if you notice, that the engine has become “clumsy”, “heavy” – most probably, the Stratified charge is turned off.

Third – unevenness of the performance of the engine appears. In idle – they are manifesting as low-quality maintaining of idle (for example, the idle “flows”, when you turn the steering wheel, once the car is parked; turning on and off powerful consumers – AC, window heating, etc.); while driving – the vibration of the engine can be felt: so – some of the cylinders are not working with full power.

Fourth – the engine doesn’t give full power, vibrations are strong. Services suggest replacing the injectors, but the replacement does not improve the situation cardinally.

Fifth – problems of the NOx system (and consequences – turned-off Stratified charge) can be the reason for the error messages regarding fuel trim, trim of Lambda probes, the reason for misfires, shivering of the engine, strong unevenness of the engine performance. Before replacing any components – check the “health” of the NOx system.

And finally – if the engine does not use a Stratified charge, could be problems (and very often there are) with the shifting of the automatic gearbox. The gearbox can behave clumsy, shift with jerks, shift late. The creation of the adaptations of the gearbox switching is malfunctioning.

How to check the Stratified charge for F10/11?

1. Warm-up the engine to the working temperature. In regular circumstances, DME turns on the Stratified charge, if the engine temperature reaches around 60oC.

2. Start driving. While the engine runs idle, the Stratified charge will not get turned on. But, if the Stratified charge was turned on, the engine will run in it for a certain time also in idle, when the car will be stopped. For how long time – depends on several conditions (“health” of the NOx catalytic converter, exhaust temperature, does the DME measures the leaking of the injectors in idle, or performs other service procedures, etc.).

3. Observe live data, using BMW Diagnostic Software ISTA D/+or INPA.

If you use ISTA D/+: perform full identification of the car; choose DME and press the “Call up ECU functions” button.

In the DME menu choose the ”Diagnostics scan” section, ”Oxygen sensor control” subsection, select ”Signal, Oxygen sensor before catalytic converter” and ”Signal, Oxygen sensor 2 before catalytic converter”, press ”Read status”.

These data will show, with what fuel mixture the engine of your car runs:

1.99 .. 2.01V: Homogeneous mode; Lambda 0.99 .. 1.01
2.40 .. 3.00V; Stratified charge; Lambda 2 .. 3
2.25 .. 2.30V; Homogeneous lean; Lambda around 1.5

How-to-check-the-Stratified-charge-for-BMW-F10-F11-1

In the picture: the engine works in Homogeneous mode with Lambda around 1.00

Start driving and drive evenly with speed 50 .. 100km/h.

If the engine uses a Stratified charge, the indications of the sensors of both banks should be around 2.40 .. 3.00V.

After each 10 .. 40 seconds, the indications of the sensors from 2.40 .. 3.00V will reduce for several seconds under 2.00V. At this moment the NOx catalytic converter is cleaned from nitrites. Evaluate the time interval between these cleaning cycles:

30 .. 40 seconds – perfect health of the NOx catalytic converter
10 .. 15 seconds – very bad health of the NOx catalytic converter
20 .. 30 seconds – acceptable health of the NOx catalytic converter (the more, the better)

Check the usage of a Stratified charge during a longer period of time – part of hidden problems can turn odd Stratified charge after a certain time (5 .. 30 minutes). So – perform a longer drive, check Stratified charge several times, after each 5 .. 15 minutes. In a perfect scenario – perform the test for at least 3 .. 5 driving sessions. If during any of the sessions the engine does not use a Stratified charge, perform the repeated test after a short moment (5 .. 10 minutes). Temporarily turned off Stratified charge does not indicate problems – DME can perform some specific test or adaptation procedure (measure the injectors, adapt the Tank ventilation valve, EGR, etc.)

Note: during tests, don’t drive faster than 100km/h, because increased speed can initiate the desulfation session. During the desulfation session, Stratified charge is turned off, the engine works with Lambda 0.95.

If you use INPA: choose DME; open Fuel mixture menu ../F5/F6. Evaluate the Lambda value for both banks.

Lambda 0.99 .. 1.01 – Homogeneous mode
Lambda 2.00 .. 3.50 – Stratified charge
Lambda ap. 1.50 – Homogeneous lean mode
Start driving and drive evenly with speed 50 .. 100km/h.

If the engine uses a Stratified charge, indications of Lambda of both banks should be 2.00 .. 3.50.

After each 10 .. 40 seconds the Lambda indications from 2.00 .. 3.50 will reduce to 0.90 for several seconds. At this moment the NOx catalytic converter will be cleaned from nitrites. Evaluate the time interval during these cleaning cycles.

30 .. 40 seconds – perfect health of the NOx catalytic converter
10 .. 15 seconds – very bad health of the NOx catalytic converter
20 .. 30 seconds – acceptable health of the NOx catalytic converter (the more, the better)

How-to-check-the-Stratified-charge-for-BMW-F10-F11-2

Example: the engine uses Stratified charge with Lambda around 3

How-to-check-the-Stratified-charge-for-BMW-F10-F11-3

Example: the regeneration of the NOx catalytic converter is in progress

Check the usage of a Stratified charge during a longer period of time – part of hidden problems can turn odd Stratified charge after a certain time (5 .. 30 minutes). So – perform a longer drive, check Stratified charge several times, after each 5 .. 15 minutes. In a perfect scenario – perform the test for at least 3 .. 5 driving sessions. If during any of the sessions the engine does not use a Stratified charge, perform the repeated test after a short moment (5 .. 10 minutes). Temporarily turned off Stratified charge does not indicate problems – DME can perform some specific test or adaptation procedure (measure the injectors, adapt the Tank ventilation valve, EGR, etc.)

Note: during tests, don’t drive faster than 100km/h, because increased speed can initiate the desulfation session. During the desulfation session, Stratified charge is turned off, the engine works with Lambda 0.95.

If the engine uses Stratified charge stable and the regeneration interval of the NOx catalytic converter corresponds to its good health – congratulations! Your car is fine! If the engine does not use a Stratified charge, uses it rare/unstable, for a short moment, the regeneration is often (each 10 .. 15 seconds) – unfortunately, the car has problems with the NOx system.

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