Graeme and any other inquiring minds,
With the original roadster distributor, the ignition trigger is supplied
by the breaker points as the contacts open and close. With the EI
distributor,
the trigger is instead, provided by the reluctor (on the distributor
rotor
shaft) and the pick-up coil (inside the distributor). As the reluctor
rotates, the amount of magnetic flux passing through the pick-up coil
changes. The changing magnetic flux generates an electrical signal in
the pick-up coil. This is commonly referred to as the Hall effect.
This electrical signal is conducted into the IC ignition module (mounted
on the side of the distributor), which triggers the primary current
running through the ignition coil. This generates high voltage in the
secondary winding of the coil, which is conducted to the spark plugs.
The IC ignition module (attached to the side of the distributor housing)
performs multiple functions with 5 individual circuits:
1. Spark timing signal monitoring circuit This circuit detects the
ignition signal sent from the distributor pick-up coil, and amplifies
the signal.
2. Lock-preventing circuit This circuit cuts off the ignition coil
primary current when the ignition switch is ON and the engine is
stationary. If the ignition coil primary current is allowed to flow
under such conditions,
excessive current will be drawn because of low internal resistance of
the ignition coil. This would result in an abnormal temperature rise in
the ignition coil or discharged battery. These malfunctions will be
prevented by this lock-preventing circuit.
3. Duty control circuit This circuit controls the ratio of the
ignition coil primary current ON-OFF time periods, in one cycle of
ignition
operation. This is equivalent to the dwell angle of the conventional
points type distributor. In order to provide high performance spark
firing over a wide range of driving speeds, this duty is controlled by
the source voltage and the ambient temperature, as well as by the engine
rpm.
4. Power switching circuit This circuit is used to make or break
directly, the primary circuit current of the ignition coil.
5. Current limiting circuit This circuit controls the current value so
that excessive current will not flow through the power switching
circuit.
That's about it for its theory of operation for the EI distributor.
While I'm here, I'll offer a little who's who, too:
I'm a former cake decorator for Martha Stewart Living. Oops, wrong
story.
I'm 45 years old, married with a 9 year old daughter. My passion for
automobiles was sort of initiated by my older brother, who bought a new
sports car about the time I started driving. I purchased my first car,
a '67 Mustang, from my brother. I drove this Mustang til the day I
graduated from college in
1979, when I had arranged for a car dealer to have waiting for me in my
parents' driveway a brand new 1979 Datsun 280ZX. Everybody thought I
was crazy for spending $11,000 for a car that only holds 2 people. Now
everybody thinks I'm crazy for still having it and driving it everyday
with over 350,000 miles on it. I guess I've gotten my money's worth.
I got involved with SCCA Solo 2 with the 280ZX and won a few titles in
the Southwest Division in the '80's. Then for a second car, I bought a
'75
MGB, another 2 seater. I had a head-on collision in it with a Ford LTD,
so I
put it out of its misery and sent it to the auto graveyard (best place
for
it). I vowed to never buy another convertible until I found out Datsun
made one and it was competitive at the national level in SCCA Solo 2 in
CSP. How
convenient!!!
After I found a Datsun 2000 advertised, I drove it 150 miles home. The
PO didn't bother to tell me when I called, that the top was gone, it was
in the 40 F temperature range and all I had for upper attire was a
T-shirt. On top of that, my buddy who went with, drove my 280ZX back at
100 mph the entire way home, despite my request to take it easy since I
didn't really know what the roadster's engine was made of. I spent the
next year doing a full mechanical makeover and Solo 2 prep. Then came
the flares and paint. You can see it before and after at
http://www.picturetrail.com/gboone
I got my B.S. in Mechanical Engineering in 1979 from the University of
Arkansas. Worked for Mobil Oil for 12 years as a project engineer,
rotating
equipment specialist, equipment reliability engineer, and major project
manager. Now I live in Cheyenne, Wyoming, the roadster capital of the
world, oops I mean the capital city of Wyoming :-) Been doing a variety
of engineering work since, for various entities like DOE, oil companies,
chemical companies, etc. Been unemployed for the past 14 months and
working on starting my own business in internet marketing, automotive
related, of course. Tired of being the victim of layoffs.
Have a nice weekend.
Gary Boone
'70 SRL311-13767
WyCROC member http://www.wycroc.org/
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