RE: [T3] Distributor Plug Wires....

[Matthew Jones <m@vw1600e.org.uk>]

> From: J. Jonik
> * What performance effects if dist. plug wires are in
> wrong spot ...

I've been thinking about this and trying to work out what the
effect would be:

The FI points connect the outside 2 wires to the central wire.
When the cam comes round, it breaks one connection, then the other.
One outside wire triggers one pair of injectors. The other outside
wire triggers the other pair.

If the 2 outside wires are swapped, it will simply trigger the
injectors at the wrong point in the cycle. The fuel will sit in
the inlet port until the valve opens later. This won't affect
performance much, if at all.

If the centre wire is swapped with one of the outside wires, only
1 pair of injectors will be triggered properly. But what would
happen to the other trigger? ...

For the sake of explanation, lets say that this arrangement has
a "good" side (centre wire 'C' on one side, one trigger wire 'X'
in the centre); and a "bad" side ('X' in the centre, and the other
trigger wire, 'Y', on the other side).

In this situation, if both points are closed, all 3 wires are
still connected together. If the "bad" side opens on its own,
the ECU still sees an open circuit from 'C' to 'Y', so it would
still trigger 1 set of injectors.

If the "good" side opens on its own, C & X go open circuit,
triggering one set of injectors. But X and Y would still be
connected together, so the ECU would also see Y disconnecting
from C at the same time, i.e. Y has also just gone open circuit,
and then trigger the other set at the same time.

So, depending on what order the points open, and whether both
are ever open together, you would either get all injectors firing,
but with odd fuel timing; or you would get one side firing twice,
leading to very rich running, possibly even flooding / hard to
start. But I *think* you would never get only 1/2 the injectors
firing.

Did anyone stay with me through that?! Its really hard to explain
without a diagram or hand waving. Have I got this right?

I know the reality is more complex, as it depends on the electronics
at the ECU end of the wires, whether the common wire is 0, 12V or
whatever, pull ups, loads etc. etc.

--
Matt. UK.
'73 1600e FB.

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