Walnut Shell Blasting

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Is your BMW, Mini or Audi running rough and down on power even though there is no check engine light and you have taken care of all your recommended maintenance?  If so, you may need a walnut shell blasting decarbon service.

First off the “Why” your car is having issues.  Modern engines often use a type of fuel injection called direct injection.  The direct injection means that the fuel is injected directly into the combustion chamber instead of the intake tract.  This design allows an engine to yield more power while using less fuel.  However, the consequence of this design is that the fuel injectors are no longer placed before the intake valve, but directly in the cylinder itself.

The disadvantage of this is that the regular bathing and cleaning of the intake valves by the cleaning agents in modern fuel no longer takes place.  The intake valves are now only in contact with the air and other blow-by gases from the crankcase; where substantial quantities of fuel and oil can be found.  Over time these lead to deposits of carbonized fuel and oil in the intake tract as well as on the intake valves themselves.  This is often called carbonizing (hence the decarbon service name).  As the carbon continues to build it will have a detrimental effect on the efficiency of your engine; such as, valves that may not close properly anymore, rough idle, vibrations, diminished throttle response, and increased oil consumption.

Since this carbonizing effect is an inevitable byproduct of the direct injection design, it cannot be prevented.  Additives to fuel are useless as the fuel does not come into contact with the intake tract or valves.  We have seen the carbon buildup as early as 20,000 miles with the average recommended service at 45,000-65,000 mile intervals.


BMW Walnut shell blasting

Before and after walnut shell blasting service


So, what can you do?

There are a couple of options to remedy this, such as disassembling the head and manually scrubbing the valves and intake tract with a highly aggressive cleaning solution.  This is very labor intensive (read costly).  The more efficient method is to use some special tools that use a combination of high pressure air and fine walnut shell granules to clean the intake tract.  These granules hit the carbon at high speed and remove it entirely, while at the same time being soft enough to not damage the metal of the intake tract and the valves.

If you are feeling any above symptoms, or you are due for this service please give Alex’s Autohaus a call for all of your BMW repair, Audi repair and Mini repair and service needs.