[s-cars] S6 Tach and Speedo gone Whacko- Zeroing out and spinning forward

[Paul Gailus]

Brian,

It's possible that you might be getting EMI (electromagnetic interference) from
the ignition system into the tach and speedo sensors and/or their associated wiring.
This would be more likely to happen with external ignition coils and relatively long
high voltage wiring to the plugs. Is this the setup that you're using?
If so, you might try to keep the coil secondary wires (and primary wires for that matter)
separated away from the sensor wiring as much as possible.

Also, you might try routing a ground wire from the coil's secondary winding ground
connection over to the engine head or valve cover. Route this wire along with the plug
wires. The idea here is to minimize the "loop area" formed by the plug wires and their
associated ground return back to the coils. The smaller the loop area, the less effective
it is for radiating interference. Shielding the plug wires is another possibility if necessary.

You could also be getting interference coupling through "ground loops" between the
ignition and speed sensor systems. This can be minimized by proper routing of the
various grounding wires and connections.

Paul

-----Original Message-----
>From: brian bilotti <vinnieb2 at yahoo.com>
>Sent: Dec 13, 2006 11:41 PM
>To: Robert Rossato <bob.rossato_af at cox.net>, s-car-list at audifans.com
>Subject: Re: [s-cars] S6 Tach and Speedo gone Whacko- Zeroing out and	spinning forward
>
>Bob,
>
>I just had the full 034 system installed by 034, read
>no more MOTRONIC ECU. I also had the 034 Motorsport
>Engine mounts installed.
>Can you say, "NO GIVE WHATSOVER"? I also have a
>Urethane snub mount. I suspect it's not that :-(
>
>The ONLY thing that cuts out is the speedo and tach.
>Heck today I even got the speedo to go 360 degrees
>FORWARD, so that makes 180 MPH??? The motor's not
>cutting out, ONLY the tach and speedo have gone
>whacko.
>
>bb
>--- Robert Rossato <bob.rossato_af at cox.net> wrote:
>
>> Brian, 
>> 
>> I don't have a definitive solution, just some random
>> rambling early
>> morning thoughts.
>> 
>> I don't recall this issue before, but one
>> possibility may be that you
>> have a bad connection or a break in a wire that is
>> opening when the
>> engine rocks in its mounts during acceleration.  I
>> was having a similar
>> issue with my oil temperature wiring.  If I
>> accelerated hard the gauge
>> would drop to zero and then come back up when I
>> eased up on the throttle
>> and the engine leveled off in its mounts.
>> 
>> I don't think it's the speed sensor connection at
>> the left side of the
>> transmission as that would only cut out the
>> speedometer, not the tach.
>> And since the tach gets its signal from the ECU, I'm
>> not sure what wire
>> in the engine bay could be intermittent that would
>> cause the tach to cut
>> out, but not kill the engine.
>> 
>> Bob
>> 
>> 
>> 
>> > -----Original Message-----
>> > From: s-car-list-bounces at audifans.com 
>> > [mailto:s-car-list-bounces at audifans.com] On Behalf
>> Of brian bilotti
>> > Sent: Wednesday, December 13, 2006 12:44 AM
>> > To: s-car-list at audifans.com
>> > Subject: [s-cars] S6 Instrument Cluster Zeroing
>> out
>> > 
>> > 
>> > S-Heads,
>> > Got a weird issue with my IC. On boost, thank you
>> > Javad and 034, the tach and speedo needles zero
>> > out/drop to zero then shoot back up again.
>> > 
>> > Wasn't there a writeup about this somewhere?
>> > 
>> > Thanks
>> > 
>> > bb
>> 
>> 
>
>
>
> 
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