$699 BMW TWIN-Turbo Decarb Service (six-cylinder only, V8 please call for price)
Due to modern unburned hydrocarbon (UHC) regulations, vapors from the crankcase are usually vented into the intake stream in order to prevent oil droplets from escaping through the exhaust. In a port injection engine, these droplets are ‘washed off’ the neck of the intake valve by a relatively constant stream of gasoline droplets. In a direct injection turbocharged engine, the gasoline doesn’t touch intake side of the valve. As a result, the droplets have a tendency to bake onto the valve and significantly reduce performance. To add to this effect, many advanced direct injection turbocharged engines also include exhaust gas recirculation in order to lean out the combustion mixture and reduce in-cylinder temperatures for certain combustion modes (reducing NOx emissions). Since direct injection combustion has the ability to produce far more soot than premixed combustion (port injection), the problem is magnified.

Even more alarming is that these deposits can dislodge and damage other downstream components (turbochargers, catalytic converters, etc.). Manufacturers have added systems to capture these oil droplets and particulates, but no system is 100% effective. As a result, there are many disappointed early adopters with large repair bills.

BMW tried to offer in-tank and spray-on valve cleaners, however their effects are minimal on an engine that already has carbon buildup. Only a thorough blasting of the valves and head ports using factory blaster and walnut shell media will provide a proper cleaning, as illustrated below.

                                     BEFORE DECARB SERVICE:

                                     AFTER DECARB SERVICE: