Intake Clogging

From TDIClub

This phenomenon refers to the buildup of soot and oil mixture in the intake ducts. Due to EPA emissions regulation, and other environmental factors, VW has designed a Exhaust Gas Recirculation ([EGR]) valve. This allows a portion of exhaust gasses to be recirculated back into the intake, reducing the amount of excess oxygen, limiting the generation of [NOx].

Due to high content of sulphur in North American diesel fuels, exhaust is rather sooty. This mixes with another aspect of diesel engine operation: Crank Case Vent (CCV) gasses. These result from blow-by gasses generating a positive pressure inside the crank case. Because these must be vented to prevent leaking seals, they are also recirculated back into the intake for complete combustion. Unfortunately the violent operation inside the diesel engine churns the oil into a fine mist which is carried by the gasses, combining with the soot from ERG to form a sticky goop that plagues the inside of intake ducts, hampering the amount of air that can get through, negatively affecting performance.

Any TDIer can spot this affliction simply by noticing lack of power to the wheels. Remedies include

• using higher-cetane, low-sulphur diesel ([ULSD] coming to North America in fall, 2006)
• using fuel additives
• using biodiesel
• performing the CCV mod, consisting of some type of air/oil separator
• performing EGR modification, consisting of blocking off the EGR valve and/or reporgramming the ECU