[s-cars] Hi Mileage S6, what would you do? Also S6 No Start Update

[Paul Gailus]

I don't think that the camshaft sensor is absolutely needed to have
the engine start and run, but not having it would lead to less than optimal
running and emissions.
The camshaft hall sensor is needed to resolve the 180 degree phase
ambiguity between the camshaft and crankshaft in a 4-cycle engine.
For example, it's needed to determine whether the piston is reaching
TDC on a compression stroke or on an exhaust stroke.
If you don't have the camshaft sensor, then you'd have to fire the coils
on both the exhaust and compression strokes like in a waste-spark system.
This would dissipate more energy and heat in the coils and POS'es,
and compromise many of the advantages of having separate coils
per cylinder in the first place.
Also, the injectors would also have to be fired once per crank revolution,
so some of the advantages of sequential over batch firing would be lost.

If I recall correctly, there are coil-per-plug engines out there that revert
to waste-spark operation as a "limp home" mode if the cam sensor fails.
Now _that_ would be a useful feature to have.

Paul

----- Original Message -----
From: Jack Gagnon <bullitt at gwi.net>
To: <s-car-list at audifans.com>
Sent: Monday, January 09, 2006 10:23 PM
Subject: RE: [s-cars] Hi Mileage S6, what would you do? Also S6 No Start
Update


> Hey, I was thinking....
>
> If the car will run fine as long as it is not turned off, why is the cps
> needed in the first place?  Is it used to determine timing, or is it just
a
> safety feature in case the t-belt breaks?  If it is a safety feature, it
is
> pretty much useless since the valves will get trashed as soon as it breaks
> anyway.  Looking at scott m's site, it appears that it will indicate a
> possible improper valve timing issue.  If that is all it does and it is a
> royal pita to swap, can it be deleted somehow?  I have heard of a few
people
> having a slipped t-belt, but I have never heard of the check engine light
> and the code telling them so.
>
> what do ya think?
>
> Jack
>
> -----Original Message-----
> From: s-car-list-bounces at audifans.com
> [mailto:s-car-list-bounces at audifans.com]On Behalf Of Aaron Taylor
> Sent: Monday, January 09, 2006 2:30 PM
> To: 'Dave Forgie'; s-car-list at audifans.com
> Subject: RE: [s-cars] Hi Mileage S6, what would you do? Also S6 No Start
> Update
>
>
> Ahh
> Now I don't feel so bad.
> I only paid 500$ to have mine installed!
> Aaron
>
> -----Original Message-----
> From: s-car-list-bounces at audifans.com
> [mailto:s-car-list-bounces at audifans.com] On Behalf Of Dave Forgie
> Sent: Sunday, January 08, 2006 9:58 AM
> To: s-car-list at audifans.com
> Subject: [s-cars] Hi Mileage S6, what would you do? Also S6 No Start
Update
>
> Dave:  I agree with Forrest Bradshaw's list.  Some of those need to be
> done but only a few of them will actually strand you on the side of the
> road.  In my experience, these are the cam position sensor (CPS)  and
> the fuel pump.
>
> The cam sensor will probably throw a Check Engine light (CEL) to give
> you a bit of a heads up - but not much. The problem is if you get a CEL
> and you turn the engine off to check whatever it is, the engine may not
> restart because the ECU looks to the CPS for a signal before it will
> trigger the fuel pump to come on.  No signal = no fuel = Stranded.  I am
> a strong advocate of replacing the CPS at the second timing belt change,
> if not before.
>
> In my experience, the original fuel pumps are good to about 100,000 mi
> (160,000 km) - after that, you are living on borrowed time.  The fuel
> pump will just fail.  Period.  Minimal subtle warnings (no CEL), like a
> little longer to start one morning.  When mine failed, I had this
> warning sign which, like a minor chest pain, I ignored. I then set off
> on a trip.  Car was fine that day but after being parked for a night
> meeting, it refused to start - the fuel pump had failed.  Since I was
> away from home and away from my mechanic, the car had to be flat-bedded
> to the nearest dealer who proceded to economically 'rape' me. ($800 to
> install a $120 pump).
>
> I have since replaced that pump (a perfectly good VDO) with a Bosch as a
> potential solution for RS2-related fueling issue.  I wrote a procedure
> up which you may want to follow.  It isn't that difficult if your tank
> level is down (which you can arrange IF you do a pre-emptive replacement
> - which I advocate):
>
> http://forums.audiworld.com/s4s6/msgs/86586.phtml
>
> Dave F.
>
>
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