Originally Posted by kbsilver
Just curious if anyone knows. The walnut blasting/cleaning of the head and intake valves. Is this done with the head ON the engine, or is it removed? I do find it interesting that in most warrenty cases for cabon build, they replace the head rather than clean it (I expect it is cleaned at some point and made available as a refurb replacement).
I'll presume there is no way to meet emission standards, even with more DEF usage, without resorting to EGR (I would go for that!). Am I correct that the primary need for EGR is to reduce NOx?
Yes, the EGR and the SCR are to reduce NOx emission:
"Beginning with model year 2009, BMW will introduce 2 diesel
models for the first time since 1987. The E90 and E70 will be
available with the new M57D30T2 (US) engine.
The two new models will meet the EPA Tier 2, Bin 5 requirements
and will be considered “50 State” legal. In order to comply with
these new stringent regulations, both vehicles have the latest in
emission control and engine management technology.
Both vehicles will be equipped with the latest Selective Catalytic
Reduction system to reduce unwanted NOx emissions. Also, the
X5 will have an additional Low Pressure EGR system to further
assist in the reduction of NOx."
Here what BMW say about the EGR:
"Exhaust Gas Recirculation (EGR)
During normal operation, the exhaust gas recirculation is controlled
based on the EGR ratio. During regeneration of the diesel particulate
filter, it is conventionally controlled based on the air mass.
The monitoring function also differs in this way: During normal
operation a fault is detected when the EGR ratio is above or below
defined limits for a certain period of time.
This applies to the air mass during regeneration of the diesel particulate
filter. In order to monitor the high pressure EGR cooler, the
temperature after the high pressure EGR cooler is measured with
the bypass valve open and close with the engine running at idle
speed. A fault is detected if the temperature difference is below a
For the low pressure EGR cooler (only E70), the measured temperature
after the low pressure EGR cooler is compared with a calculate
temperature for this position. A fault is detected if the difference
exceeds a certain value.
Each of these faults is stored reversible. If the fault is determined in
two successive driving cycles, an irreversible fault is stored and the
MIL is activated."