My fix for the grounding problems is to dip the entire van in liquid solder.
When it hardens: Presto, perfect grounding!

Yeah I just know some spoilsport will find a minor problem or two with this.
Just don't tell me.

Mike

Friday?

On 4/10/03 9:58 AM, "Steve Delanty" <laurasdog@WEIRDSTUFFWEMAKE.COM> wrote:

> Jay wrote:
>> Grounds and clean connections are the key. I have added extra body to
>> engine ground wires, as well as  wires from the alternator and the AFM
>> casting.  All the connections are cleaned and assembled with di-electric
>> grease.
>
> Grounds, grounds, grounds...
>
> I believe that part of the problem is that VW engineers violated
> one of the most important rules of good grounding tecniques
> by grounding the ECU and some of the sensors to the body of the
> vehicle and the O2 sensor (and who knows what else) at the engine.
> Good design practice would dictate grounding ALL of the EFI components
> including the ECU to the engine ONLY. (and most modern EFI systems
> go out of their way to do this)
>
> Grounding the ECU at the body and O2 at the engine means that the
> ANY resistance (and there is always some) in the ground strap from
> engine to body will cause an error voltage to be added to the output of
> the O2 sensor.
>
> Consider the following facts for your amusement...
> Under "normal" conditions the voltage output of the O2 sensor is
> approximately 0.5 volts. A voltage output of 1.0 volt would indicate an
> EXTREMELY rich condition, and a voltage of 0.25 volts would be
> extremely lean, so it's obvious that small voltage errors can make a pretty
> big difference between what the O2 sensor sees and what the ECU *thinks*
> the O2 sensor sees.
>
> When the alternator is producing current, the ground return path for said
> current back to the alternator travels through the ground braids. Since these
> braids have a finite resistance, there *will* be a voltage drop across them.
> How much? Well, if the alternator is producing 30 amps, and the ground
> braid resistance is 0.01 ohms, then the voltage difference between the
> body of the car (where the ECU is grounded) and the engine (where the O2
> is grounded) will be 0.3 volts, with the body voltage being positive
> relative to
> the engine. (that is the engine is 0.3 volts more negative than body)
> So... this 0.3 volts introduced by grounding errors is subtracted from the 0.5
> volts that the O2 sensor puts out, and suddenly the ECU only sees 0.2 volts
> !!!
> Holy Cr@p!  We're way to lean says the ECU, and cranks the mixture up to
> rich as hell..
>
> The problem is worsened by the fact that the DC offset voltage caused by
> charging current is only an average, and an error of 0.3 volts will also have
> an AC component riding on it caused by the 3-phase alternator output, which
> causes the peak voltages to be much higher. Also, "Load dump" (which is brief
> high voltage spikes caused when electrical loads are suddenly removed)
> causes very short duration but high current spikes to pass through the
> ground braids and I saw brief voltage peaks well in excess of 1 volt between
> the body and engine when I was measuring. This means that the O2 sensor
> input to the ECU actually goes to a voltage BELOW ground (negative with
> respect to ground) periodically.
>
> I think the ECU just can't cope with this BS on the O2 line and eventually
> goes into "stupid mode" until the power is reset.
>
> Some folks have said that disconnecting the O2 sensor made their vanagon
> syndrome go away. Yep. Makes sense to me...
>
> I believe that what REALLY needs to be done, is to find ALL the wires that
> ground the EFI system to the body (ECU and all sensors) and remove these
> grounds from the body and ground them ALL at the engine only. Only in
> this way can all error voltages caused by charging current passing through
> imperfect engine to body ground straps be eliminated
>
> Since our digifants, don't do it right, the next best thing is to add plenty
> of extra heavy duty grounding, preferably directly from the alternator to some
> body point removed from the EFI ground locations. There will always be
> *some* error voltage present on the O2 line this way, but you can probably
> reduce it to an insignificant amount.
>
> And again, the noise suppression capacitor on the back of the alternator
> is an important item. It not only helps remove some of the 3-phase AC
> component off the charging voltage, but it helps absorb the brief voltage
> spikes caused by alternator load dump.  Get one if ya ain't got one!
>
> So there. That's what *I* thnk about digifant and it's silly ground system...
>
> Happy motoring!
> Steve
> '86 Westy
>