[Vwdiesel] 0w30 Mobil 1

Lee Hillsgrove hillsgrove at tds.net
Mon Mar 4 20:48:04 EST 2002

>  Oh, Oh!  Question!! I have a question here!

  All right! Loren, with a question! Not every day you see that!

>  What's the feasibility of disconnecting the EGR on the TDI's?  I know on
>many other engines you can simply disconnect the line to it and tada!  No
>more extra soot.  Is there a sensor or such that will put out a fault code
>if you do such a thing?

 Yes, there is. Or, more accurately, a system that will trigger the dreaded
"Check Engine" light. At least in America. Other countries may or may not
have the same regulations.

  As was mentioned by other posters, some truly crafty individuals on Fred's
TDI club have pooled their knowledge and discovered that a vacuum switch
triggered by the signal intended to open the EGR valve could be used to cut
in a diode to one of the Mass Airflow Sensor wires. The ECU looks at the MAF
when EGR is triggered to "see" a reduction in airflow past the sensor since
the exhaust gas would be taking up a portion of the volume originally
occupied by the intake air. The OBDII system is required to verify the
integrity of the emission control systems, and this drop in flow when the
EGR is triggered is it's way of checking that system. It happens to be that
the voltage drop reported by the MAF to the ECU when EGR is triggered is
about .7 volt. Fortuitously, the voltage drop across a common silicon diode
is.......   .7 volt. Isn't that convenient? When the ECU asks for EGR, the
vacuum switch opens and shunts the intercepted MAF signal across the diode,
and the ECU stays fat, dumb, and happy. No check engine light.

 Of course, this information is only of use to someone using their TDI for
off-road or closed-circuit racing purposes only. To do otherwise would be
illegal, immoral, and possibly fattening.

 Such off-road vehicles may, with the incorporation of a better crankcase
ventilation system and the use of a quality oil, see the benefit of greatly
reduced or eliminated intake manifold clogging. Some owners have reported
serious clogging after as little as 50K miles. The soot from the EGR
combines with the oil vapors from the CCV system and form a thick paste that
constricts the intake manifold. Not good.

 It just seems so much like taking a percentage of
>your garbage and making you use it each time you make stew for the
>family.  Ewwww!

  That's about the size of it.......  Or, roughly equivalent to running a
tube from YOUR tailpipe to your intake. Think about it. Not a desirable
situation!  :-))


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