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BMW and MINI – LSPI in Gasoline Direct Injection (GDI) Engines – Why High Quality Oil and Frequent Changes Are Important
BMW and MINI (as well as most other manufacturers) are producing more and more engines that incorporate intricate engine management and control systems in order to meet emissions requirements, reduce vehicle weight (smaller engines) and increase power output. While it seems that the goals of reducing engine size to achieve higher fuel economy and lighter vehicle weight, while producing more power are at opposite ends of the field, the manufacturers have been achieving both of these goals through the use of Gasoline Direct Injection (GDI) and forced induction (turbo or super charging)*.
These small displacement, forced induction, GDI engines are running within a very tight optimum operational envelope in order to achieve the desired fuel economy and power output. The tightest area of the engine management mapping is what we might call “cruise”. This is when the vehicle is running at a more or less steady speed, in the top gear. During this operational parameter, the engine is being run as lean as possible (for best economy and emissions). Contrary to what we might think, the engine is under a fair amount of load (cylinder pressures and temperatures) when in this mode. Additionally, if the load is moderately increased (not enough to cause a gear downshift), by a slight uphill grade, minor acceleration, etc., the engines cylinder pressures and temperatures are significantly increased.
Due to all of the above points, these small displacement, forced induction, GDI engines can exhibit a phenomena known as LSPI (Low Speed Pre-Ignition). Similar to detonation, this condition creates extremely high cylinder pressures and can be highly destructive to the engine. We commonly know pre-ignition and detonation as “knock” or “ping”. These conditions occur when the charge in the combustion chamber ignites prematurely or burns too quickly. The expanding combustion charge either is trying to push the piston down while it is still moving upward or expands in volume faster than the piston can move downward. The knock or ping we detect is the piston rattling in the cylinder bore, the cylinder head rattling on the engine block, crankshaft bearings being hammered and general distress on the engine parts.
LSPI is thought to be generated in these small displacement engines due to combustion soot or other particles from “dirty” oil that are in the combustion chambers during the compression cycle. The heat in the combustion chambers heats the particles to a burning point and the particles act as a source of ignition to the compressed charge. As soon as the fuel begins to be injected, the charge is ignited … before the spark plug fires. This is the pre-ignition condition.
Is there anything we can do to help assure that our BMW or MINI engines don’t suffer from LSPI? Since it is believed that a potential source of the LSPI is particles in the combustion chamber, we would suggest the following:
1) Forced induction GDI engines tend to produce more soot in the combustion cycle. Therefore, use a high quality fuel system cleaner and a carbon cleaner as a periodical treatment to help prevent build-up of soot in the combustion chambers.
2) Dirty oil has a higher particular content than fresh oil, even though the oil may still be fully within its operational envelope. This particular content may contribute to the combustion chamber particles that are available for potential pre-ignition. Using a high quality synthetic motor oil and applying shorter change intervals will help to keep the particular content low.
* What is GDI and Forced Induction?
GDI injects the fuel directly into the combustion chamber at the precise moment that is optimum for cylinder combustion at any given engine operational parameter. This allows a far more exact level of engine management. In order to increase power from these smaller engines, forced induction using turbocharging or supercharging may be employed. As the name implies, forced induction “forces” additional air into the cylinders during the intake cycle. Normally, atmospheric pressure pushes the air into the cylinder as the piston falls and creates the volume in the cylinder. Forced induction adds pressure over that of the atmospheric pressure, which forces additional air mass into the cylinder. This increased air mass can now have an additional amount of fuel injected (to keep the proper air/fuel ratio). The resulting combustion is of greater power as if a larger cylinder (larger engine size) were being used. Therefore, with GDI and forced induction, a smaller engine can be made to have the power of a larger engine while also achieving higher fuel economy, compared to the larger engine.
BMW NA is performing a recall on various F56 MINI Cooper Hardtop models from the 2014 model year. Affected models were produced from Jan.,7, through July, 21, 2014. The spare wheel and tire assembly may have been assembled to the vehicle with a standard non-locking nut. The non-locking nut may vibrate loose and allow the spare assembly to be released from the vehicle while underway.
2014 MINI Cooper two door hardtop models produced January 7, 2014 through July 21 , 2014.
According to the recall:
” Vibrations from driving may cause the nut to loosen, allowing the wheel to separate from the car. If the spare wheel separates from the vehicle, it could become a road hazard and increase the risk of a crash.”
BMW/MINI will replace the spare wheel assembly securing nut with a self-locking nut.
The recall is planned to begin November 2014. A second notice will be send when the repair parts are available. Anticipated schedule is October 2014. Owners of affected vehicles are being notified by BMW/MINI. Further information can be obtained by contacting MINI customer relations at 1-866-275-6464.
All passenger vehicles sold in the US since 1996 are required to incorporate the OBD-II (On Board Diagnostics v-II) engine management parameters. The OBD-II systems play important roles in increasing engine efficiency (fuel economy) and reducing emissions, as well as offering useful fault codes for diagnosing various engine management faults or failures, at the expense of increased complexity. OBD-II engine management systems incorporate multiple engine sensors and operating systems. Often, the engine will have more than one of a particular sensor or operational system. The OBD-II engine management needs a way to make determinations of which part or system is in question when monitoring as well as delivering a fault code. The various fault code readers will also need to represent the location of the faults in an abbreviated, yet precise, manner.
The OBD-II system looks at the engine in regards to the groups of cylinders that are monitored collectively. In other words, the Engine management system does not typically operate and monitor all of the paraleters of each of the individual cylinders. The cylinders are grouped into collective groups, or BANKS, as follows:
* Most 4-cylinder engines have just one bank; Bank-1 = cylinders 1 through 4 are all operating under one collective group.
* Most 6-cylinder engines have two banks; Bank-1 = cylinders 1 through 3, Bank-2 = cylinders 4 through 6
* Most 8-cylinder engines have two banks; Bank-1 = cylinders 1 through 4, Bank-2 = cylinders 5 through 8
* Most 12-cylinder engines have two banks; Bank-1 = cylinders 1 through 6, Bank-2 = cylinders 7 through 12
In the examples above, the cylinders in BANK-1 are operated as a group. they are also monitored as a group (in most cases). Likewise, the cylinders in BANK-2 are operated and monitored as a group.
In addition to the cylinder banks, the system may also monitor the intake and exhaust sides of the cylinder head as one group or separately. The confusion comes in when these are also referred to as BANKS. How do you know if the BANK reference in a fault code is referring to the cylinders or the intake/exhaust sides of the cylinder head? We’ll look at this in a bit, but before we do let’s add to the confusion, shall we?
If there is more than one of a given sensor, we may see these labeled as Sensor-1 and Sensor-2. We could also see them as Sensor-A and Sensor-B. Typically, this will be limited to cylinder head and camshaft sensors and oxygen sensors. For the oxygen sensors, the pre-cat sensors will be “1″ or “A” and the after=cat sensors, “2″ or “B”. For cylinder head sensors and systems the intake side of the cylinder head would be “1″ or “A” and the exhaust side, “2″ or “B”. Unless, they are being referred to as Bank-1 or Bank-2. Got that?
The apparent confusion can indeed actually be understood, but we need to have a grasp on the methodology in order to properly decipher the codes from different fault code readers. Let’s look at some examples:
Cylinder banks will always be related to as Bank-1 and Bank-2 if the engine does operate as two Banks. In other words, a typical 6-cylinder, V-8, V-10 or V-12 will be represented with both Banks 1 & 2. Note that on BMW V8, V10 & V12 engines, the right side (Passenger side on, left-hand drive models) is Bank-1 (cylinders 1-4, 1-5 or 1-6). A fault code that is Bank dependent will always include the Bank number in the code (EXAMPLE: Fuel Trim Bank-1). The exception to this can happen with engines that are operated as one Bank, such as a 4-cylinder. Codes may include the Bank-1 designation, or may not mention the cylinder Bank, since there is only one. Note that the “Bank” designation can be used for intake and exhaust when there is only one cylinder bank …. OR …. on a straight 6-cylinder for the intake and exhaust since the two cylinder banks do not have separate intake and exhaust systems for each group of cylinders. Keep reading, it gets better!
Sensor or Cylinder Head Intake & Exhaust Numbers:
Different code readers will call out sensors either numerically or alphabetically (1 & 2 or A & B). For cylinder head related sensors or issues, 1 and A will be for the intake side, 2 and B will be for the exhaust side. As stated earlier, oxygen sensors will be labeled 1 or A for the pre-cat sensors and 2 or B for the after-cat sensors.
Let’s look how this pans out, for a better understanding.
1) BMW straight 6-cylinder engine or BMW or MINI 4-cylinder engine with an intake cam position sensor fault code -
* Fault code says Camshaft Sensor A – Since this is a straight-6, even though operationally there are two cylinder banks, there is only one intake and one exhaust camshaft. The single camshafts cover both cylinder banks and there would only be one sensor per camshaft. Therefore, there is no relevent cylinder bank. We just need to know which camshaft sensor. e can now know that Sensor-A is the intake cam position sensor.
* Fault code says Camshaft Sensor 1 – Same notes as above. Remember, 1 and A are used interchangeably.
* Fault code says Camshaft Sensor Bank 1 – Since the system is not differentiating between the two groups of cylinder banks (as outlined above), it is using the Bank designation as the Intake/Exhaust delineation. Bank-1 is for the intake cam position sensor. Bank-2 would be for the exhaust cam sensor.
* Fault code says Camshaft sensor Bank-1 Sensor-1 (or A) – Similar to the first two examples, but this particular code reader is looking at the whole line of 6-cylinders as one bank because there is just one cylinder head and one set of cams for all of the cylinders. Therefore, there is only a Bank-1 when looking at faults pointing at items in the cylinder head, such as the camshaft position sensors. Finally, the last part of the code call-out is noting the intake camshaft (sensor 1 or A).
2) BMW V8, V10, V12 or straight 6-cylinder engine or BMW or MINI 4-cylinder engine with an oxygen sensor fault code -
* Fault code says Oxygen Sensor Bank-2, Sensor-1 – This is indicating that the pre-cat oxygen sensor for bank-2 (6-cyl = 4-6, V8 = 5-8, V10 = 6-10, V12 = 7-12, would not apply to a 4-cyl which only has one bank). Therefore, it would be one of the two sensors that is mounted in the exhaust manifolds (in this case the Bank-2 manifold) prior to the catalytic converter sections (sensor-1 or A) and is typically accessed from above. A fault code for sensor-2 (or B) would be for the after-cat sensor.
Click below for oxygen sensors:
3) BMW V8, V10 or V12 engine with and intake camshaft position sensor fault code on the driver (left) side cylinder bank -
* Fault code says Camshaft sensor Bank-2, Sensor-1 (or A) – This is indicating that Bank-2 is the left side and Sensor-1 indicates that the fault is at the intake camshaft sensor. Note that on a V style engine, there will always be at least two banks (BMW) and the right side bank is always bank-1.
This can get confusing, but if you apply the above points to think about how the code is represented and what type of engine it is referencing, you can figure out the actual meaning quickly.