distributor swap (clarification)

Ben Swann benswann at comcast.net
Sun Apr 2 11:16:40 EDT 2006



The use of  5 window or single window Hall wheel does not necessarily
pertain to use of knock sensing.  They are merely two different ways of
measuring where the engine cam position is and the single window sensor is
used in conjunction with two crank position sensors and so thoretically more
accurate.  Don't know why VAG used both methods, but suspect it had to do
with parallel development efforts and in general, the single window with
crank senesors supercedes the 5 window method.  But again it does not
indicate use of a knock sensor or not.


Read the spec. manuals and you will find that the 5 window hall system used
in conjunction with some CIS-E3 engines uses knock sensing and can retard
timing on a cylinder by cylinder basis and there is no vacuum diaphrgm on
the distributor.  Also, the single window sensor is used on the earlier CIS
turbo cars - turbo 5000 and (Ur) Quattro but does not incorporate knock
sensing, as that came in the later years.


And as pointed out, it is not a CIS or EFI thing - often the injection
subsystem is independent of the ignition subssytem, although things get
rather tightly coupled as time progresses and more interdependant.  So hope
this clarifies although probably adds to the muddy waters.



benswann at comcast.net


[Date: Thu, 30 Mar 2006 10:23:49 -0700

From: "Kenneth Keith" <auditude at gmail.com>

Subject: Re: distributor swap

To: 200q20v at audifans.com, rletsinger at gmail.com


Well, it's not really a CIS vs. EFI thing either.  It's a knock sensing
thing.  So any turbo motor that has knock sensing, such as MC(CIS), or any
normally aspirated motor with knock sensing, such as 7A (EFI), will have a
single window dizzy.  I don't know about the high compression n/a 10v motors
like NG (CIS), but I suspect they would also have the single window wheel.
BUT those 10v distributors are different from 20v dizzies in ways other than
the number of windows in the sheet metal cup for the hall sensor.


With the 5 window dizzy, the ECU can't control timing AFAIK.  Instead it's
done by vacuum advance (is it advance or retard?) on a Coupe GT, for
example.  The cars with the single window dizzy use the window in
combination with the flywheel teeth and timing pin to determine engine
position and adjust timing.


I hear that the n/a 7A motor has only two maps, we can call them "good gas"
and "bad gas."  I believe the 3B has a more sophisticated setup where it can
step down the timing and boost more gradually than in just two steps.





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