An interesting intake / clutch vent update - rerouting the clutch vent pipe

Rerouting the clutch vent pipe – It is interesting that on the manual transmission 993 there is a clutch vent pipe that runs up along the passenger side of the engine to a rubber hose that directs the venting to the pre-filter side of the engine air intake box. An emission control idea?? It seems to me this arrangement has three value-added features. 

• First, it clogs the filter with any abrasive debris that comes out of the pipe. It also 
• Allows any abrasive friction material that gets past the filter into the engine and it 
• Ensures when the clutch is not used carefully the burning friction odor is immediately piped into the engine bay and sucked into the cabin heating system adding a certain something special to the driving experience.

At this point, I rigged up a prototype breather that replaces the rubber hose leading to the engine air intake box. It is an easy slip-on solution made from home plumbing parts and an aftermarket automotive breather element is completely reversible and may be of interest to some.

Here is the parts list:

• Summit Racing breather SUM-G3405

And the following home store PVC plumbing parts:

• 1" pvc to female pipe adapter ( breather screws on to this)
• 1" pvc 45 Degree elbow
• 1" pvc pipe (to join the elbow to the pipe adapter)
• 1.25" rubber flex coupling with hose clamps (to clamp assembly to existing pipe in the engine compartment.

Some may question if it does anything at all. My understanding is that: 

• The clutch/flywheel section has veins in it that pump a little air through the clutch housing up into the vent tube in the engine compartment to aid in keeping the clutch cool and; 
• Confirming this if the clutch is not used carefully one immediately smells burnt clutch in the cabin sucked in through the heating intake duct in the engine compartment;
• When inspecting a used air filter there is a dirt spot corresponding to where the clutch vent tube enters the air cleaner housing and; 
• the last time I cleaned the Air Flow sensor between the air cleaner housing and the throttle body it was covered in an even grey debris coating I attributed to being fine clutch dust the filter did not capture.

The update replaces the rubber "hose elbow" called out as #7 in the below diagram and part number 993.110.333.00 "plug" called out as #12 can be purchased to plug the open hole in the intake airbox.