Hello Paul-

We got a free lesson in electromagnetics today.After I emailed
yesterday,
we went to run the engine again & it ran terrible!Terry had diddled with
some of the computer settings, so we thought perhaps we'd screwed
something
up.We reviewed the settings & discoverered the EC2 tach setting was way
off -- 572 vs the not-to-be-changed value of 515.Terry fired up again &
all seemed well.

Until... I noticed the EM2 reporting continually decreasing line
voltages...

I looked at the switch panel, and saw we had the externally-regulated
alternator off-line.I flicked it back online... and... disaster.
Suddenly
the engine was trying desperately to stop & could not be adjusted to run
smoothly.Flicking the alternator off resulted in fairly smooth running.
Every time the alternator was brought on line, the engine went bananas.
As
soon as it went off line, the engine became much smoother.

Here's a test for the group:Why is this happening?Here's an old photo
which pinpoints the problem for those with sharp eyes...

Mark (Rocky Mtn High)


--



The alternator wire (output) bundled with the CAS wires

Rino



Lynn & Rino have it (mostly) correct.The problem was the field wire from
the alternator being bundled with the CAS proximity sensor wires.The
field
wire switches on & off rapidly (that being how a regulator controls an
alternator to generate power at whatever desired voltage).The rapid
switches induce pulses in the CAS proximity sensor wires, which confuse the
EC2 & result in a rough running engine.

Mark

** extra bonus question **

As one can see from the original photo, I am running the model alternator
which was stock for the RX-7.How does one shut down a stock alternator of
this type while the engine is running?;-)

Mark Supinski


Mark,

The Aero-Electric has lots of info on how to do a "crowbar over-voltage"
protection circuit on an internally regulated alternator.Basically, you
have to use a contactor to open the battery lead.

I chose to go with dual Geo Metro alternators and convert them to work with
external regulators.With an external regulator, you interrupt the field
circuit with a SPST switch to shut it down.Years back, Contact magazine
did a story on this subject.

Mark S.